Earthquake alert issuance device, earthquake alert issuance method, and program

Abstract

To provide an earthquake warning issuing device, an earthquake warning issuing method, and a program capable of improving the reliability of an earthquake warning issued according to an earthquake that has occurred.SOLUTION: An integration unit configured to estimate an index value of water pressure change by performing a filtering process using a high-pass filter having a predetermined frequency after integrating a water pressure value observed by a water pressure gauge included in each of observation devices disposed at a plurality of observation points provided on a submarine cable installed on a seabed once; SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an earthquake warning issuing device, an earthquake warning issuing method, and a program. [Background technology]

[0002] To ensure the safety of running trains, it is necessary to detect earthquakes early and stop trains if necessary. For this reason, earthquake early warning systems have been in operation for some time, which detect earthquakes early and issue earthquake warnings to stop running trains. In conventional earthquake early warning systems, in order to control train operations when an earthquake occurs, a method has been introduced in which an earthquake warning is issued when the observed S waves (secondary waves), which are the main waves of an earthquake, exceed a threshold set for each observation point based on information on S waves (hereinafter referred to as an "S wave warning"). In contrast to this, in recent years, a method has been developed in which the initial motion of P waves (primary waves), which arrive before S waves (information immediately after the arrival of P waves), is used to estimate the earthquake parameters of an earthquake (e.g., the location of the epicenter and the magnitude of the earthquake), and an earthquake warning is issued based on the estimated earthquake parameters (hereinafter referred to as a "P wave warning"). This method has been put into practical use to speed up train operation control when an earthquake occurs.

[0003] Since then, large-scale ocean-floor observation networks have been established, such as the Japan Trench Ocean Bottom Earthquake and Tsunami Observation Network (S-net) operated by the National Research Institute for Earth Science and Disaster Resilience. Ocean-bottom seismometer information, which represents seismic waves observed by ocean-bottom seismometers included in these ocean-bottom observation networks, is being used to issue early earthquake warnings in the railway industry. Because ocean-bottom seismometers are installed closer to the epicenter than land-based seismometers, the travel time difference between P waves and S waves is smaller than that of land-based seismometers, and the benefits of applying P-wave warnings are not as great as those of applying P-wave warnings to land-based seismometers. For this reason, early earthquake warning systems using ocean-bottom seismometer information from ocean-bottom seismometers use S-wave warnings, in which thresholds for determining whether to issue an earthquake warning are preset for each observation point. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Hiroyuki Miyakoshi, Shunroku Yamamoto, Akihiro Gion, Maki Kamiyama, Shuichi Tadani, Atsushi Watanabe, and Taku Kunugi, "Data Processing for Utilizing Ocean Bottom Seismometer Information for Railway Early Earthquake Warning," Journal of the Railway Technical Research Institute, Vol. 29, No. 1, pp. 35-40, January 2015 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional earthquake early warning systems, which use ocean-bottom seismometers to issue S-wave alerts, issue an earthquake alert when a single ocean-bottom seismometer detects seismic waves generated by an earthquake. In other words, conventional earthquake early warning systems issue earthquake alerts based on seismic waves observed at a single observation point. While issuing earthquake alerts using a single observation point, such as S-wave alerts, has the advantage of being able to issue earthquake alerts quickly based on seismic waves detected by an ocean-bottom seismometer, it also has the disadvantage of being prone to overestimating or underestimating the magnitude of earthquakes. Furthermore, the amplification characteristics of seismic waves beneath the seafloor vary more than those of seismic waves on land. Therefore, even for earthquakes of similar magnitude and epicenter distance, the magnitude of seismic motion can vary depending on the location of the ocean-bottom seismometer where the seismic waves pass through. For this reason, with conventional early earthquake warning systems, there are cases where inappropriate train travel control is implemented, such as when train travel control is not implemented when an earthquake occurs that requires it, or when control is implemented when an earthquake occurs that does not require it, which can result in a decrease in train travel safety and economic losses.

[0006] The present invention has been made based on the recognition of the above-mentioned problems, and aims to provide an earthquake warning issuing device, an earthquake warning issuing method, and a program that can improve the reliability of earthquake warnings issued in response to an earthquake that has occurred. [Means for solving the problem]

[0007] The earthquake warning issuing device, earthquake warning issuing method, and program according to the present invention employ the following configuration. (1): An earthquake warning issuing device according to one embodiment of the present invention is an earthquake warning issuing device that includes an integration unit that once integrates the water pressure values ​​observed by the water pressure meters provided in each of the observation devices arranged at a plurality of observation points on an undersea cable installed on the seabed, and then performs filtering using a high-pass filter of a predetermined frequency to estimate an index value of the water pressure change, and an earthquake warning issuing unit that controls the issuance of earthquake warnings based on the index value of the water pressure change.

[0008] (2): In the above aspect (1), the earthquake warning issuing unit determines whether the index value of the water pressure change exceeds a predetermined earthquake warning threshold, and issues the earthquake warning if the index value of the water pressure change exceeds the earthquake warning threshold.

[0009] (3): In the above aspect (2), the earthquake warning threshold is calculated based on a predefined second distance attenuation formula as the maximum value of the index value of the water pressure change estimated in the event of an earthquake of a magnitude calculated based on measurement data from seismometers installed along the railway line and a predefined first distance attenuation formula, and the first distance attenuation formula is calculated and predefined based on the acceleration value of seismic motion represented by measurement data from earthquakes that have occurred in the past, and the second distance attenuation formula is calculated and predefined based on the index value of the water pressure change from the water pressure gauge that observed earthquakes that have occurred in the past.

[0010] (4): In the above aspect (1), an estimation unit is further provided that estimates the magnitude of the earthquake that has occurred for each observation point based on the index value of the water pressure change, and the earthquake warning issuing unit determines whether the earthquake magnitude is equal to or greater than a predetermined earthquake magnitude threshold, and issues the earthquake warning if the earthquake magnitude is equal to or greater than the earthquake magnitude threshold.

[0011] (5): In the above aspect (4), the estimation unit determines the arrival time of the P wave and the arrival time of the S wave from the earthquake for each observation point based on the index value of the water pressure change, estimates the epicenter distance between each observation point and the epicenter of the earthquake for each observation point based on the difference between the arrival time of the P wave and the arrival time of the S wave, and estimates the magnitude of the earthquake based on the index value of the water pressure change, the epicenter distance, and a predefined third distance attenuation formula.

[0012] (6): In the above aspect (5), the estimation unit estimates the magnitude of the earthquake by substituting the index value of the water pressure change and the epicenter distance into the third distance attenuation formula.

[0013] (7): In the above aspect (6), the earthquake magnitude threshold is the magnitude of an earthquake that may cause damage along the railway line, and the third distance attenuation formula is calculated and defined in advance based on the index value of the water pressure change of the water pressure gauge that observed earthquakes that occurred in the past.

[0014] (8): A method for issuing an earthquake warning according to one embodiment of the present invention is a method for issuing an earthquake warning, which includes integrating once the water pressure values ​​observed by the water pressure meters provided in each of the observation devices arranged at a plurality of observation points on an undersea cable installed on the seabed, filtering using a high-pass filter of a predetermined frequency to estimate an index value of the water pressure change, and controlling the issuance of an earthquake warning based on the index value of the water pressure change.

[0015] (9): A program according to one embodiment of the present invention is a program that causes a computer to once integrate water pressure values ​​observed by water pressure meters provided on each of observation devices placed at multiple observation points on an undersea cable installed on the seabed, and then performs filtering using a high-pass filter of a predetermined frequency to estimate an index value of water pressure change, and controls the issuance of earthquake warnings based on the index value of water pressure change. [Effects of the Invention]

[0016] According to the present invention, it is possible to improve the reliability of earthquake warnings issued in response to an earthquake that has occurred. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an example of a usage environment of an earthquake early warning system including an earthquake warning issuing device according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an example of an earthquake waveform obtained by processing information about an earthquake observed by an ocean-bottom observation network by an earthquake warning issuing device. [Figure 3] FIG. 1 is a diagram showing an example of a comparison of information about earthquakes observed by an ocean-bottom observation network. [Figure 4] 3 is a diagram schematically showing an example of a method for calculating an earthquake warning threshold value for determining whether or not an earthquake warning needs to be issued, which is set in the earthquake warning issuing device according to the first embodiment. FIG. [Figure 5] FIG. 3 is a diagram showing an example of an earthquake warning threshold value set in the earthquake warning issuing device according to the first embodiment for determining whether or not an earthquake warning needs to be issued. [Figure 6] 1 is a diagram illustrating an example of the configuration of an earthquake warning issuing device according to a first embodiment. [Figure 7] 5 is a flowchart showing an example of a process flow for issuing an earthquake warning in the earthquake warning issuing device according to the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the configuration of an earthquake warning issuing device according to a second embodiment. [Figure 9]10 is a flowchart showing an example of a process flow for issuing an earthquake warning in an earthquake warning issuing device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of an earthquake warning issuing device, an earthquake warning issuing method, and a program according to the present invention will be described with reference to the drawings.

[0019] [Earthquake Early Warning System Usage Environment] 1 is a diagram showing an example of a usage environment of an earthquake early warning system including an earthquake warning issuing device according to an embodiment. The earthquake warning issuing device 100 is a device that controls the issuance of an earthquake warning AL in an earthquake early warning system that detects an earthquake E that has occurred early and issues an earthquake warning AL to stop a train T as necessary.

[0020] In an earthquake early warning system, an earthquake warning issuing device 100 detects an earthquake E that has occurred using information observed by a large-scale seafloor observation network NW, such as the Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S-net), which is promoted and maintained by the National Research Institute for Earth Science and Disaster Resilience. In response to the detected earthquake E, the earthquake warning issuing device 100 issues an earthquake warning AL to stop a train T traveling on a railway line R. The seafloor observation network NW includes, for example, a submarine cable laid on the seabed over several hundred kilometers, and multiple observation devices OB (multiple observation points) are arranged at intervals of several tens of kilometers. Each observation device OB includes at least, for example, an ocean-bottom seismometer SS and an ocean-bottom pressure meter SW. The ocean-bottom seismometer SS is composed of measuring devices such as a speedometer and an accelerometer, and is provided to monitor seismic motion caused by the earthquake E that has occurred. The seabed water pressure gauge SW is, for example, composed of a water pressure gauge, and is installed mainly to monitor the occurrence of tsunamis from changes in water pressure caused by Earthquake E. The changes in water pressure caused by Earthquake E observed by the seabed water pressure gauge SW also contain information indicating the seismic waves (vibration waveforms representing seismic motion) W caused by the earthquake E that has occurred.

[0021] In the undersea observation network NW, each end of the undersea cable is connected to a land station MS (for example, land station MS-1 and land station MS-2). Each land station MS sequentially (in real time) acquires various information (data), including information about the earthquake E observed by the ocean-bottom seismometer SS and the ocean-bottom pressure gauge SW, through bidirectional data communication via the undersea cable. More specifically, each land station MS acquires information (data) about the observed earthquake E from the ocean-bottom seismometer SS included in each observation device OB, for example, at a frequency of 100 [Hz]. Each land station MS acquires information (data) about the observed earthquake E from the ocean-bottom pressure gauge SW included in each observation device OB, for example, at a frequency of 10 [Hz]. Each land station MS sequentially (in real time) outputs the information (data) acquired from the ocean-bottom seismometer SS and the ocean-bottom pressure gauge SW to the earthquake warning issuing device 100. The information (data) that each land station MS sequentially (in real time) outputs to the earthquake warning issuing device 100 is associated with information indicating the locations of the ocean-bottom seismometer SS and ocean-bottom water pressure gauge SW, i.e., the location of the observation point where the observation device OB is located. Each land station MS may be configured to output the information (data) acquired from each ocean-bottom seismometer SS and ocean-bottom water pressure gauge SW to a management device (not shown) operated by an organization that has jurisdiction over the ocean-bottom observation network NW, and this management device (not shown) may be configured to sequentially (in real time) output the information (data) to the earthquake warning issuing device 100.

[0022] The SW submarine pressure gauge is an example of a "water pressure gauge."

[0023] The earthquake warning issuing device 100 controls the issuance of an earthquake warning AL based on information (data) about earthquake E observed by the ocean bottom seismometer SS and the ocean bottom pressure gauge SW, which is output by each land station MS (which may be a management device not shown). Figure 1 shows an example of how an earthquake warning AL is issued to a train T running on a track R in response to an earthquake E that has just occurred.

[0024] The earthquake warning issuing device 100 does not have to issue an earthquake warning AL directly to the train T. For example, the earthquake warning issuing device 100 may output information indicating that an earthquake warning AL will be issued to a traffic control system that manages the operation of the train T, and the traffic control system may instruct the driver operating the train T to stop (halt). If the running of the train T is controlled by the power supply to the train T, the earthquake warning issuing device 100 may output information indicating that an earthquake warning AL will be issued to a power supply facility such as a substation that supplies power for the running of the train T that issued the earthquake warning AL, and the power supply facility may stop the power supply to the corresponding section, thereby stopping the train T (halting the train).

[0025] In the following explanation, information (data) regarding Earthquake E observed by the ocean-bottom seismometer SS will be referred to as "ocean-bottom seismometer information," and information (data) regarding Earthquake E observed by the ocean-bottom water pressure meter SW will be referred to as "ocean-bottom water pressure meter information."

[0026] The seismic waves W representing the seismic motion caused by Earthquake E include P waves (primary waves), which are the first to arrive and are the main cause of vertical ground motion (so-called vertical shaking) by vibrating in the direction of their propagation, and S waves (secondary waves), which are the second to arrive and are the main cause of horizontal ground motion (so-called horizontal shaking) by vibrating perpendicular to the direction of their propagation. The ocean-bottom seismometers SS and ocean-bottom pressure meters SW are installed closer to the epicenter of Earthquake E than seismometers (not shown) installed on land. For this reason, the travel time difference between the P and S waves in the seismic waves W observed by the ocean-bottom seismometers SS and SW is smaller than the travel time difference between the P and S waves in the seismic waves W measured by land-based seismometers (not shown).

[0027] (First embodiment) The earthquake warning issuing device 100 of the first embodiment controls the issuance of an earthquake warning AL based on ocean bottom seismometer information and ocean bottom pressure gauge information related to S waves, which are the main motions of an earthquake. More specifically, the earthquake warning issuing device 100 determines the magnitude of seismic motion caused by earthquake E, represented by the ocean bottom seismometer information observed by the ocean bottom seismometer SS, based on earthquake warning thresholds set for each observation point, i.e., each observation device OB, and issues an earthquake warning AL if it is determined that the magnitude of the seismic motion exceeds the earthquake warning threshold. The earthquake warning issuing device 100 determines the magnitude of the change in water pressure caused by earthquake E, represented by the ocean bottom pressure gauge information observed by the ocean bottom pressure gauge SW, based on earthquake warning thresholds set for each observation point (each observation device OB), and issues an earthquake warning AL if it is determined that the magnitude of the change in water pressure exceeds the earthquake warning threshold.

[0028] Here, we will explain an example of seismic motion based on ocean-bottom seismometer information and ocean-bottom water pressure gauge information. FIG. 2 shows an example of seismic waveforms processed by the earthquake warning issuance device 100 from information about Earthquake E (ocean-bottom seismometer information and ocean-bottom water pressure gauge information) observed by the ocean-bottom observation network NW. FIG. 2 shows an example of temporal changes in each seismic waveform representing seismic motion. (a-1) and (a-2) of FIG. 2 show an example of seismic waveforms (displacement waveforms of seismic motion) based on ocean-bottom seismometer information acquired by the earthquake warning issuance device 100. The displacement waveforms of seismic motion shown in (a-1) and (a-2) of FIG. 2 are waveforms obtained by integrating the velocity values ​​of seismic motion represented by the ocean-bottom seismometer information once in the time domain or by integrating the acceleration values ​​of seismic motion twice in the time domain. (b-1) and (b-2) of FIG. 2 show an example of seismic waveforms (waveforms of changes in water pressure) based on ocean-bottom water pressure gauge information acquired by the earthquake warning issuance device 100. The waveforms of water pressure changes shown in (b-1) of Figure 2 and (b-2) of Figure 2 are waveforms of values ​​(hereinafter referred to as "water pressure change index values") obtained by integrating the water pressure values ​​due to seismic motion represented by the ocean-bottom water pressure gauge information once in the time domain and then filtering using a high-pass filter (i.e., a high-pass filter (HPF)). Here, the high-pass filter used by the earthquake warning issuing device 100 for filtering is, for example, a 0.16 [Hz] high-pass filter. The displacement waveform of seismic motion shown in (a-1) of Figure 2 and the waveform of water pressure change shown in (b-1) of Figure 2 are information observed by the ocean-bottom seismometer SS and the ocean-bottom water pressure gauge SW provided in the same observation device OB, that is, information observed at the same observation point. The displacement waveform of the seismic motion shown in (a-2) of Figure 2 and the waveform of the change in water pressure shown in (b-2) of Figure 2 are seismic waveforms based on information observed by an ocean-bottom seismometer SS and an ocean-bottom water pressure meter SW (ocean-bottom seismometer information and ocean-bottom water pressure meter information at the same observation point) equipped on another observation device OB, which was placed at a different observation point from the observation device OB that observed the seismic waveforms shown in (a-1) of Figure 2 and (b-1) of Figure 2.

[0029] As can be seen from the displacement waveform of the seismic motion shown in Figure 2(a-1) and the water pressure change waveform shown in Figure 2(b-1), and the displacement waveform of the seismic motion shown in Figure 2(a-2) and the water pressure change waveform shown in Figure 2(b-2), the observation device OB, located at the same location, can obtain similar seismic waveforms by performing corresponding processing on the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS and the ocean-bottom pressure gauge information observed by the ocean-bottom pressure gauge SW. In other words, by integrating the water pressure values ​​represented by the ocean-bottom pressure gauge information observed by the ocean-bottom seismometer SW once in the time domain and filtering them, the change in water pressure caused by the shaking of the seafloor due to Earthquake E can be obtained as information similar to the magnitude of the seismic motion due to Earthquake E, represented by the velocity and acceleration values ​​represented by the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS.

[0030] Here, we will explain an example of a comparison between the magnitude M of earthquake E observed by a public institution such as the Japan Meteorological Agency and the maximum velocity value of seismic motion (so-called peak ground velocity (PGV)) indicated by ocean-bottom seismometer information observed by ocean-bottom seismometers SS equipped in each observation device OB of the ocean-floor observation network NW, and the maximum water pressure change index value based on water pressure indicated by ocean-bottom pressure gauge information observed by ocean-bottom pressure gauges SW, when the epicenter distance Δ of earthquake E is, for example, less than 50 km. Figure 3 shows an example of a comparison of information about earthquake E observed by the ocean-bottom observation network NW (ocean-bottom seismometer information and ocean-bottom pressure gauge information). Figure 3(a) shows a comparison between the magnitude M of earthquake E observed by a public institution such as the Japan Meteorological Agency and the maximum velocity value (PGV) indicated by each ocean-bottom seismometer SS. Figure 3(b) compares the magnitude M of earthquake E observed by public institutions such as the Japan Meteorological Agency with the maximum water pressure change index value obtained from the water pressure values ​​due to seismic motion observed at each ocean bottom pressure gauge SW.

[0031] As can be seen from the comparison results shown in Figure 3(a) and Figure 3(b), the maximum velocity value (PGV) and the maximum water pressure change index value both increase as the magnitude M increases. In other words, the water pressure change index value based on the water pressure values ​​observed by the ocean-bottom pressure gauge SW also represents a value according to the magnitude of the earthquake E that occurred, just like the velocity and acceleration values ​​observed by the ocean-bottom seismometer SS.

[0032] However, the maximum velocity values ​​(PGV) shown in FIG. 3(a) have a larger variation in values ​​for the same magnitude M than the variation in the maximum water pressure change index values ​​shown in FIG. 3(b). Furthermore, the maximum velocity values ​​(PGV) shown in FIG. 3(a) exhibit values ​​similar to those observed in large earthquakes E of magnitude M=7.0 or greater, even when the magnitude M of earthquake E is relatively medium, i.e., M=6.0 or less. Therefore, if the earthquake warning issuing device 100 issues an earthquake warning AL based on values ​​similar to those observed in an earthquake E of magnitude M=7.0 when an earthquake E of magnitude M=6.0 or less occurs, train T will be stopped even though it does not need to be stopped. In other words, the variation in the maximum velocity values ​​(PGV) shown in FIG. 3(a) may reduce the safety of train T's operation and cause economic losses.

[0033] Thus, for a relatively medium-sized earthquake E, it is considered that the water pressure change index value based on the water pressure values ​​represented by the sea-bottom pressure gauge information observed by the sea-bottom pressure gauge SW equipped in the observation device OB can provide a value that more robustly represents the magnitude M than the velocity value of seismic motion represented by the sea-bottom seismometer information observed by the sea-bottom seismometer SS. For this reason, when the earthquake E that has occurred is relatively medium-sized, it is considered more appropriate for the earthquake warning issuing device 100 to control the issuance of an earthquake warning AL using the water pressure change index value based on the water pressure values ​​represented by the sea-bottom pressure gauge information observed by the sea-bottom pressure gauge SW, rather than the velocity value of seismic motion represented by the sea-bottom seismometer information observed by the sea-bottom seismometer SS equipped in the observation device OB.

[0034] Figure 3(a) shows an example of comparing the magnitude M of earthquake E observed by a public institution such as the Japan Meteorological Agency with the maximum ground velocity value (PGV). However, it is believed that the same results can be obtained by comparing the maximum acceleration value of seismic motion (so-called peak ground acceleration (PGA)) indicated by ocean-bottom seismometer information observed by the ocean-bottom seismometer SS with the magnitude M instead of the maximum ground velocity value (PGV).

[0035] For this reason, earthquake warning thresholds for determining whether or not to issue an earthquake warning AL for each of the ocean-bottom seismometer information and the ocean-bottom water pressure gauge information are set in advance in the earthquake warning issuing device 100 for each observation device OB. Each earthquake warning threshold may be determined and set in advance by the earthquake warning issuing device 100, or may be set in advance for the earthquake warning issuing device 100 by a computer device (not shown). The earthquake warning issuing device 100 then determines whether or not to issue an earthquake warning AL based on whether or not the maximum velocity value of the seismic motion (which may be the maximum acceleration value of the seismic motion) represented by the ocean-bottom seismometer information observed by each ocean-bottom seismometer SS and the maximum water pressure change index value based on the water pressure value represented by the ocean-bottom water pressure gauge information observed by each ocean-bottom water pressure gauge SW each exceed the corresponding earthquake warning thresholds that have been set.

[0036] Here, we will explain each earthquake warning threshold that is set in advance in the earthquake warning issuance device 100. Fig. 4 is a diagram that schematically shows an example of a method for calculating an earthquake warning threshold that is set in the earthquake warning issuance device 100 according to the first embodiment and that is used to determine whether or not an earthquake warning AL needs to be issued. Fig. 5 is a diagram that shows an example of an earthquake warning threshold that is set in the earthquake warning issuance device 100 according to the first embodiment and that is used to determine whether or not an earthquake warning AL needs to be issued. Each earthquake warning threshold that is set in advance in the earthquake warning issuance device 100 is calculated using the following procedure.

[0037] (Earthquake Warning Threshold Calculation Procedure P1): The magnitude M of earthquake E, which exceeds a threshold (hereinafter referred to as the "earthquake motion threshold") for shaking (acceleration due to seismic motion) that could potentially cause damage to train T along the railway line, i.e., along track R, is calculated using an acceleration attenuation formula. Figure 4 shows a schematic diagram of how magnitude M is calculated using earthquake warning threshold calculation procedure P1 based on the seismic motion that travels along land plate PL and reaches the area of ​​track R along which train T is traveling, after earthquake E is caused by the subduction of sea-side plate PS beneath land-side plate PL. The seismic motion threshold is predetermined, for example, to 80 gal, depending on conditions such as structures along track R. In earthquake warning threshold calculation procedure P1, the magnitude M of earthquake E, which exceeds the seismic motion threshold (e.g., 80 gal), is calculated by applying the acceleration value of the seismic motion measured by a seismometer (not shown) to the acceleration attenuation formula. The distance attenuation formula for acceleration is a formula that is predefined by calculating using the acceleration values ​​represented by the measurement results of earthquakes E that occurred in the past, which are stored in advance, for example, using a seismometer (not shown) installed on land, in other words, a formula that is empirically determined from earthquakes E that occurred in the past.

[0038] The distance attenuation formula for acceleration is equivalent to the formula used to calculate the magnitude M of earthquake E that exceeds the threshold of seismic motion (earthquake motion threshold) that could cause damage to train T in a conventional early earthquake warning system that uses ocean bottom seismometers SS to issue S-wave warnings, that is, that controls the issuance of earthquake warnings using the threshold exceedance method.

[0039] In the earthquake warning threshold calculation procedure P1 described above, the magnitude M of earthquake E that exceeds the earthquake motion threshold is calculated using the distance attenuation formula for acceleration corresponding to the acceleration [gal] due to seismic motion, but the magnitude M of earthquake E may also be calculated using the distance attenuation formula for velocity corresponding to the velocity [kine] due to seismic motion. In this case, the procedure should be equivalent to the earthquake warning threshold calculation procedure P1 described above. Therefore, a detailed description of the procedure for calculating the magnitude M of earthquake E that exceeds the earthquake motion threshold using the distance attenuation formula for velocity corresponding to the velocity [kine] due to seismic motion will be omitted.

[0040] The distance attenuation formula for acceleration is an example of a “first distance attenuation formula.” For example, the measurement results of earthquake E that occurred in the past using a seismometer (not shown) installed on land are an example of “measurement data.”

[0041] (Earthquake Warning Threshold Calculation Procedure P2): When earthquake E of magnitude M calculated in earthquake warning threshold calculation procedure P1 occurs, the velocity value of the seismic motion observed by the ocean-bottom seismometer SS is estimated (calculated) using the seismic motion index value (hereinafter referred to as the "seismic motion index value") measured by a seismometer (not shown) installed on land and the velocity attenuation formula corresponding to the ocean-bottom seismometer SS. Figure 4 shows a schematic diagram of the calculation of velocity values ​​using earthquake warning threshold calculation procedure P2 based on the seismic motion caused by earthquake E that travels along the land-side plate PL and reaches the observation device OB, i.e., the ocean-bottom seismometer SS. In earthquake warning threshold calculation procedure P2, the velocity value of the seismic motion caused by the earthquake E that occurred, as represented by the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS, is applied to the velocity attenuation formula corresponding to the ocean-bottom seismometer SS to estimate (calculate) the maximum velocity value caused by the seismic motion that exceeds the seismic motion threshold (e.g., acceleration value = 80 [gal]). The velocity attenuation formula for the ocean-bottom seismometer SS, like the acceleration attenuation formula for the land-based seismometer (not shown) used in earthquake warning threshold calculation procedure P1, is a formula that is pre-defined by accumulating ocean-bottom seismometer information from past earthquakes E observed by the ocean-bottom seismometer SS and calculating using the velocity values ​​represented by this accumulated ocean-bottom seismometer information. In other words, although the accumulated velocity values ​​are different, the velocity attenuation formula for the ocean-bottom seismometer SS is also a formula empirically determined from earthquakes E that are the same as or different from past earthquakes E measured by a land-based seismometer (not shown). The maximum velocity value estimated (calculated) in earthquake warning threshold calculation procedure P2 is set as the earthquake warning threshold for the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS.

[0042] The velocity distance attenuation formula corresponding to the ocean bottom seismometer SS is equivalent to the formula used to estimate (calculate) the earthquake warning threshold (maximum velocity value) for the ocean bottom seismometer information observed by the ocean bottom seismometer SS in conventional early earthquake warning systems that use ocean bottom seismometer SS to issue S wave warnings.

[0043] Figure 5(a) shows an example of the comparison between magnitude M and maximum velocity value (PGV) shown in Figure 3(a), with the earthquake warning threshold TV set for the estimated (calculated) velocity value. As can be seen from Figure 5(a), due to variations in maximum velocity value (PGV), even for a relatively medium-sized earthquake E with a magnitude M of 6.0 or less, the maximum velocity value (PGV) may exceed the set earthquake warning threshold TV. However, if the earthquake warning threshold TV is set to a high maximum velocity value (PGV), an earthquake warning AL may not be issued in the event of an earthquake E that requires train T to be stopped. Therefore, from the perspective of improving operation stability by stopping train T as quickly as possible in the event of an earthquake E, the earthquake warning threshold TV set as shown in the example of Figure 5(a) must be considered preferable.

[0044] In the above-mentioned earthquake warning threshold calculation procedure P2, the maximum velocity value of seismic motion exceeding the seismic motion threshold is estimated (calculated) using the velocity distance attenuation formula corresponding to the ocean-bottom seismometer SS. However, in addition to or instead of the maximum velocity value, the maximum acceleration value may be estimated (calculated) using the acceleration distance attenuation formula corresponding to the ocean-bottom seismometer SS. In this case, the procedure should be equivalent to the above-mentioned earthquake warning threshold calculation procedure P2. Therefore, a detailed description of the procedure for estimating (calculating) the maximum acceleration value using the acceleration distance attenuation formula corresponding to the ocean-bottom seismometer SS will be omitted.

[0045] (Earthquake Warning Threshold Calculation Procedure P3): Furthermore, if earthquake E of magnitude M calculated in earthquake warning threshold calculation procedure P1 occurs, the water pressure change index value of the seismic motion observed by the BPF SW is estimated (calculated) using the seismic motion index value measured by a seismometer (not shown) installed on land and the distance attenuation formula for the water pressure change index value corresponding to the BPF SW. Figure 4 shows a schematic diagram of the calculation of the water pressure change index value in earthquake warning threshold calculation procedure P3 based on the seismic motion caused by earthquake E that traveled along the land-side plate PL and reached the observation device OB, i.e., the BPF SW. In earthquake warning threshold calculation procedure P3, the water pressure change index value due to the seismic motion of earthquake E, represented by the BPF information observed by the BPF SW, is applied to the distance attenuation formula for the water pressure change index value to estimate (calculate) the maximum water pressure change index value due to seismic motion exceeding the seismic motion threshold (e.g., acceleration value = 80 [gal]). The distance attenuation formula for the water pressure change index value corresponding to the bottom water pressure gauge SW, like the distance attenuation formula for velocity (or the distance attenuation formula for acceleration) corresponding to the ocean-bottom seismometer SS, is a formula that is predefined by accumulating in advance bottom water pressure gauge information from past earthquakes E observed by the bottom water pressure gauge SW and calculating using the water pressure change index value represented by this accumulated bottom water pressure gauge information. In other words, the distance attenuation formula for the water pressure change index value corresponding to the bottom water pressure gauge SW is a formula empirically determined from earthquakes E that were the same as or different from past earthquakes E, based on the water pressure change index value represented by the bottom water pressure gauge information observed by the bottom water pressure gauge SW, instead of the velocity value (or acceleration value) of seismic motion represented by the bottom water pressure gauge information observed by the ocean-bottom seismometer SS. The maximum water pressure change index value estimated (calculated) in the earthquake warning threshold calculation procedure P3 is set as the earthquake warning threshold for the water pressure change index value for the bottom water pressure gauge information observed by the bottom water pressure gauge SW.

[0046] Figure 5(b) shows an example of a comparison between magnitude M and the maximum value of the water pressure change index shown in Figure 3(b), with the earthquake warning threshold TW set for the estimated (calculated) water pressure change index value. As can be seen from Figure 5(b), the variation in the maximum water pressure change index value is smaller than the variation in the maximum velocity value (PGV) at the same magnitude M. Therefore, even in a relatively medium-sized earthquake E of magnitude M = 6.0 or less, the water pressure change index value will not exceed the set earthquake warning threshold TW. Therefore, when a relatively medium-sized earthquake E occurs, it is considered preferable to control the issuance of an earthquake warning AL based on the determination of whether the water pressure change index value exceeds the earthquake warning threshold TW, in addition to or instead of the determination of whether the maximum velocity value (PGV) exceeds the earthquake warning threshold TV. This is considered to improve the reliability and accuracy of the control of the issuance of earthquake warning AL.

[0047] The earthquake warning threshold TW is an example of an “earthquake warning threshold.” The distance attenuation formula for the water pressure change index value is an example of a “second distance attenuation formula.”

[0048] Using this procedure (earthquake warning threshold calculation procedure), the earthquake warning threshold (earthquake warning threshold TV) for the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS and the earthquake warning threshold (earthquake warning threshold TW) for the ocean-bottom water pressure gauge information observed by the ocean-bottom water pressure gauge SW are estimated (calculated) in advance for each observation device OB. Then, each estimated (calculated) earthquake warning threshold is set in advance in the earthquake warning issuing device 100. As a result, the earthquake warning issuing device 100 determines whether to issue an earthquake warning AL depending on whether the maximum velocity value of seismic motion (which may be the maximum acceleration value of seismic motion) represented by the ocean-bottom seismometer information observed by each ocean-bottom seismometer SS and the water pressure change index value based on the water pressure value represented by the ocean-bottom water pressure gauge information observed by each ocean-bottom water pressure gauge SW each exceed the corresponding earthquake warning threshold.

[0049] [Example of the configuration of an earthquake warning device] Next, an example of the configuration of the earthquake warning issuance device 100 will be described. Fig. 6 is a diagram showing an example of the configuration of the earthquake warning issuance device 100 according to the first embodiment. The earthquake warning issuance device 100 includes, for example, a storage unit 110 and a processing circuit 120.

[0050] The memory unit 110 stores a pre-set earthquake warning threshold TV for the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS and a pre-set earthquake warning threshold TW for the ocean-bottom pressure gauge information observed by the ocean-bottom pressure gauge SW. The memory unit 110 may store data and information used by each function of the processing circuit 120 included in the earthquake warning issuing device 100 when performing processing. The memory unit 110 is, for example, a storage device such as a read-only memory (ROM), a random access memory (RAM), a semiconductor memory device such as a flash memory, or a hard disk drive (HDD). While FIG. 1 shows a configuration in which the memory unit 110 is included in the earthquake warning issuing device 100, the memory unit 110 may be an external storage device connected to the earthquake warning issuing device 100. If the memory unit 110 is an external storage device, it may be, for example, a server device or storage device incorporated in a cloud computing system connected to the earthquake warning issuing device 100 via a network (not shown). The network (not shown) includes, for example, the Internet, a wide area network (WAN), a local area network (LAN), a provider device, a wireless base station, and the like.

[0051] The processing circuit 120 executes processes such as an ocean bottom seismometer information acquisition function 121, a maximum value calculation function 122, an ocean bottom water pressure gauge information acquisition function 123, a water pressure value integration function 124, and an earthquake warning issuance function 125. The processing circuit 120 realizes each function by, for example, a hardware processor executing a program (software) stored in a memory (not shown) (which may be the storage unit 110). The memory (not shown) is realized by, for example, a semiconductor memory element such as a ROM, RAM, or flash memory, a hard disk drive (HDD), an optical disk, or the like.

[0052] The term "hardware processor" refers to a circuit such as a central processing unit (CPU), a graphics processing unit (GPU), a large-scale integration (LSI), a system on chip (SOC), an application-specific integrated circuit (ASIC), or a programmable logic device (e.g., a simple programmable logic device (SPLD) or a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)). Instead of storing a program in a memory (not shown), the hardware processor may be configured so that the program is directly embedded in the circuit. In this case, the hardware processor realizes each function by reading and executing the program embedded in the circuit. The hardware processor is not limited to being configured as a single circuit, but may be configured as a single hardware processor by combining multiple independent circuits to realize each function. Multiple components may be integrated into a single hardware processor to realize each function. Multiple components may be integrated into a single dedicated LSI to realize each function. Here, the program (software) may be stored in advance in a storage device (a storage device with a non-transitory storage medium: which may be the storage unit 110) that constitutes a storage device such as a semiconductor memory element such as ROM, RAM, flash memory, or hard disk drive (HDD), or may be stored in a removable storage medium (non-transitory storage medium) such as a DVD or CD-ROM, and installed in a storage device (not shown: which may be the storage unit 110) that is provided in the earthquake warning issuance device 100 by inserting the storage medium into a drive device that is provided in the earthquake warning issuance device 100.The program (software) may be downloaded in advance from another computer device via a network (not shown) and installed in a storage device (not shown) included in the earthquake warning issuance device 100. The program (software) installed in the storage device included in the earthquake warning issuance device 100 may be transferred to a processing circuit included in the earthquake warning issuance device 100 and executed. The earthquake warning issuance device 100 may be realized in, for example, a computer device such as a personal computer or a storage device. The earthquake warning issuance device 100 may be realized in a server device or a storage device incorporated in a cloud computing system. In this case, the functions of the earthquake warning issuance device 100 may be realized by multiple server devices and storage devices in the cloud computing system.

[0053] The ocean-bottom seismometer information acquisition function 121 sequentially acquires ocean-bottom seismometer information output by the ocean-bottom seismometer SS equipped in each observation device OB. The ocean-bottom seismometer information acquisition function 121 sequentially outputs the acquired ocean-bottom seismometer information to the maximum value calculation function 122.

[0054] The ocean-bottom seismometer information acquisition function 121 may be configured to sequentially store the acquired ocean-bottom seismometer information in the memory unit 110, and the maximum value calculation function 122 may read out the ocean-bottom seismometer information stored in the memory unit 110 and output the acquired ocean-bottom seismometer information to the maximum value calculation function 122. In this case, the ocean-bottom seismometer information acquisition function 121 may be configured to always store a predetermined period of ocean-bottom seismometer information (for example, a period required to control the issuance of an earthquake warning AL) starting from the most recent ocean-bottom seismometer information, regardless of the memory capacity allocated to the memory unit 110, by, for example, storing the acquired ocean-bottom seismometer information up to the allocated memory capacity in the memory unit 110 and then overwriting the oldest ocean-bottom seismometer information with newly acquired ocean-bottom seismometer information.

[0055] The maximum value calculation function 122 estimates (calculates) the maximum value of velocity values ​​(PGV) observed by the ocean-bottom seismometer SS from the velocity values ​​of seismic motion represented by the ocean-bottom seismometer information sequentially output by the ocean-bottom seismometer information acquisition function 121. The maximum value calculation function 122 sequentially outputs the estimated (calculated) maximum value of velocity values ​​(PGV) to the earthquake warning issuance function 125. The maximum value calculation function 122 may estimate (calculate) the maximum value of acceleration values ​​(PGA) from the acceleration values ​​of seismic motion represented by the ocean-bottom seismometer information sequentially output by the ocean-bottom seismometer information acquisition function 121. In this case, the maximum value calculation function 122 sequentially outputs the estimated (calculated) maximum value of acceleration values ​​(PGA) to the earthquake warning issuance function 125.

[0056] The maximum value calculation function 122 may be configured to store the estimated maximum velocity value (PGV) (which may be the maximum acceleration value (PGA)) in the memory unit 110, notify the earthquake warning issuance function 125 that the maximum velocity value (PGV) has been stored, and have the earthquake warning issuance function 125 read out the maximum velocity value (PGV) stored in the memory unit 110, thereby outputting the estimated maximum velocity value (PGV) to the earthquake warning issuance function 125. In this case, the maximum value calculation function 122 may be configured to store the estimated maximum velocity value (PGV) in a predetermined memory area allocated in the memory unit 110, and delete the stored maximum velocity value (PGV) after the current earthquake E has subsided, thereby always storing the maximum velocity value (PGV) only when an earthquake E has occurred.

[0057] The bottom water pressure gauge information acquisition function 123 sequentially acquires bottom water pressure gauge information output by the bottom water pressure gauge SW provided in each observation device OB. The bottom water pressure gauge information acquisition function 123 sequentially outputs the acquired bottom water pressure gauge information to the water pressure value integration function 124.

[0058] The bottom water pressure gauge information acquisition function 123 may be configured to sequentially store the acquired bottom water pressure gauge information in the storage unit 110, and the water pressure value integration function 124 may read out the bottom water pressure gauge information stored in the storage unit 110 and output the acquired bottom water pressure gauge information to the water pressure value integration function 124. In this case, the bottom water pressure gauge information acquisition function 123 may be configured to always store bottom water pressure gauge information for a predetermined period (for example, a period required to control the issuance of an earthquake warning AL) starting from the most recent bottom water pressure gauge information, regardless of the storage capacity allocated to the storage unit 110, by, for example, storing the acquired bottom water pressure gauge information up to the allocated storage capacity of the storage unit 110 and then overwriting the oldest bottom water pressure gauge information with the newly acquired bottom water pressure gauge information.

[0059] The water pressure value integration function 124 estimates (calculates) the water pressure change index value observed at the bottom water pressure gauge SW by integrating once in the time domain the water pressure value represented by the bottom water pressure gauge information sequentially output by the bottom water pressure gauge information acquisition function 123, and then filtering using a high-pass filter. The water pressure value integration function 124 sequentially outputs the estimated (calculated) water pressure change index value to the earthquake warning issuance function 125.

[0060] The water pressure value integration function 124 may be configured to store the estimated water pressure change index value in the memory unit 110, notify the earthquake warning issuance function 125 that the water pressure change index value has been stored, and have the earthquake warning issuance function 125 read out the water pressure change index value stored in the memory unit 110 and output the estimated water pressure change index value to the earthquake warning issuance function 125. In this case, the water pressure value integration function 124 may be configured to store the estimated water pressure change index value in a predetermined memory area allocated in the memory unit 110, and delete the stored water pressure change index value after the current earthquake E has subsided, thereby always storing the water pressure change index value only when earthquake E occurs.

[0061] The water pressure value integration function 124 is an example of a function that "integrates the water pressure value once, then performs filtering using a high-pass filter of a predetermined frequency to estimate an index value of water pressure change." The water pressure value integration function 124 is an example of an "integration unit."

[0062] The earthquake warning issuance function 125 determines whether or not it is necessary to issue an earthquake warning AL to stop the train T, based on the maximum velocity value (PGV) (which may be the maximum acceleration value (PGA)) sequentially output by the maximum value calculation function 122 and the water pressure change index value sequentially output by the water pressure value integration function 124. At this time, the earthquake warning issuance function 125 determines whether or not the maximum velocity value (PGV) sequentially output by the maximum value calculation function 122 exceeds the earthquake warning threshold TV for velocity values ​​stored in the memory unit 110, and further determines whether or not the water pressure change index value sequentially output by the water pressure value integration function 124 exceeds the earthquake warning threshold TW stored in the memory unit 110. Then, the earthquake warning issuance function 125 determines that it is necessary to issue an earthquake warning AL when the maximum velocity value (PGV) exceeds the earthquake warning threshold TV and the water pressure change index value exceeds the earthquake warning threshold TW. The earthquake warning issuance function 125 actually issues an earthquake warning AL when it determines that it is necessary to issue an earthquake warning AL. This allows the driver of the train T for which an earthquake warning AL has been issued to safely stop (halt) the train T.

[0063] The earthquake warning issuance function 125 is an example of a function that "controls the issuance of earthquake warnings." The earthquake warning issuance function 125 is an example of an "earthquake warning issuance unit."

[0064] [Earthquake warning issuance control in earthquake warning issuing devices] Next, an example of a process in which the earthquake warning issuing device 100 issues an earthquake warning AL based on information (data) about earthquake E output by each observation device OB arranged in the seafloor observation network NW will be described. More specifically, an example of a process in which the earthquake warning issuing device 100 issues an earthquake warning AL based on ocean-bottom seismometer information output by the ocean-bottom seismometer SS and ocean-bottom water pressure gauge information output by the ocean-bottom water pressure gauge SW will be described. FIG. 7 is a flowchart showing an example of the process flow for issuing an earthquake warning AL in the earthquake warning issuing device 100 according to the first embodiment. The processes of this flowchart are repeatedly executed by the processing circuit 120 included in the earthquake warning issuing device 100 while the earthquake early warning system is operating. In the following description, it is assumed that the earthquake warning threshold TV for the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS and the earthquake warning threshold TW for the ocean-bottom water pressure gauge information observed by the ocean-bottom water pressure gauge SW are both set in advance. In the following description, for ease of explanation, it is assumed that the observation device OB outputs information (data) about earthquake E. The processing circuit 120 provided in the earthquake warning issuing device 100 controls the issuance of the earthquake warning AL based on the seafloor seismometer information output by the seafloor seismometer SS provided in the observation device OB and the seafloor water pressure gauge information output by the seafloor water pressure gauge SW.

[0065] The processing circuit 120 executes the ocean-bottom seismometer information acquisition function 121 to sequentially acquire ocean-bottom seismometer information observed and output by the ocean-bottom seismometers SS equipped in each observation device OB arranged in the ocean-bottom observation network NW (step S100). Then, the processing circuit 120 executes the maximum value calculation function 122 to estimate (calculate) the maximum velocity value (PGV) of the seismic motion of the earthquake E that has occurred from the velocity value of the seismic motion represented by the ocean-bottom seismometer information for each observation point (each observation device OB) from which the ocean-bottom seismometer information has been acquired (step S102). The processing circuit 120 may also execute the maximum value calculation function 122 to estimate (calculate) the maximum acceleration value (PGA) from the acceleration value of the seismic motion represented by the ocean-bottom seismometer information. The processing circuit 120 continues to acquire the ocean-bottom seismometer information in step S100 and to estimate (calculate) the maximum velocity value (PGV) in step S102 during subsequent processing.

[0066] Furthermore, the processing circuit 120 executes a bottom water pressure gauge information acquisition function 123 to sequentially acquire bottom water pressure gauge information observed and output by the bottom water pressure gauges SW provided in each observation device OB arranged in the seafloor observation network NW (step S110). Then, the processing circuit 120 executes a water pressure value integration function 124 to integrate once in the time domain the water pressure value due to seismic motion represented by the bottom water pressure gauge information for each observation point (each observation device OB) from which the bottom water pressure gauge information was acquired, and then performs filtering using a high-pass filter (step S112). This allows the water pressure change index value due to the seismic motion of the earthquake E that has occurred to be estimated (calculated). The processing circuit 120 continues to acquire bottom water pressure gauge information in step S110 and to integrate and filter the water pressure value in step S112 (estimating (calculating) the water pressure change index value) during subsequent processing.

[0067] The flowchart of the processing of the earthquake warning issuing device 100 shown in FIG. 7 illustrates an example in which the estimation (calculation) of the maximum velocity value (PGV) through the processing of steps S100 and S102 and the estimation (calculation) of the water pressure change index value through the processing of steps S110 and S112 are performed in this order. However, the processing of steps S100 and S102 and the processing of steps S110 and S112 are not limited to this order and may be performed simultaneously or in reverse. Furthermore, the processing of steps S100 and S110 may be performed simultaneously or in reverse, and the processing of steps S102 and S112 may be performed simultaneously or in reverse. In other words, if the processing circuit 120 performs the processing of step S100 after the processing of step S102 and the processing of step S110 after the processing of step S112, the estimation (calculation) of the maximum velocity value (PGV) and the estimation (calculation) of the water pressure change index value may be performed simultaneously or in reverse.

[0068] Next, the processing circuit 120 executes the earthquake warning issuance function 125 to determine whether the maximum velocity value (PGV) estimated (calculated) in step S102 exceeds the set earthquake warning threshold value TV for velocity values ​​(step S120). If it is determined in step S120 that the maximum velocity value (PGV) does not exceed the earthquake warning threshold value TV for velocity values, the processing circuit 120 returns the process to step S100 and repeats the acquisition of the ocean-bottom seismometer information observed and output by the ocean-bottom seismometer SS, and the subsequent processes.

[0069] On the other hand, if it is determined in step S120 that the maximum velocity value (PGV) exceeds the earthquake warning threshold TV for velocity values, the processing circuit 120 further executes the earthquake warning issuance function 125 to determine whether the water pressure change index value estimated (calculated) in step S112 exceeds the set earthquake warning threshold TW for water pressure change index values ​​(step S130).If it is determined in step S130 that the water pressure change index value does not exceed the earthquake warning threshold TW for water pressure change index values, the processing circuit 120 returns the process to step S100 and repeats the acquisition of ocean bottom seismometer information observed and output by the ocean bottom seismometer SS, and the subsequent processing.

[0070] On the other hand, if it is determined in step S130 that the water pressure change index value exceeds the earthquake warning threshold value TW for the water pressure change index value, the processing circuit 120 executes the earthquake warning issuance function 125 to issue an earthquake warning AL to, for example, a train T traveling on the track R (step S140). This allows the driver of the train T for which the earthquake warning AL has been issued to safely stop (halt) the train T.

[0071] With such a configuration and processing, the earthquake warning issuance device 100 of the first embodiment determines whether or not it is necessary to issue an earthquake warning AL in response to the earthquake E that has occurred, based on the observation results (ocean bottom seismometer information and ocean bottom pressure gauge information) of the ocean bottom seismometer SS and ocean bottom pressure gauge SW equipped in each observation device OB arranged in the ocean bottom observation network NW. In other words, the earthquake warning issuance device 100 of the first embodiment determines whether or not it is necessary to issue an earthquake warning AL in response to the earthquake E that has occurred, based on the observation results of the ocean bottom pressure gauge SW, which has small variation in the estimated (calculated) maximum value of the water pressure change index value, in addition to, or instead of, the observation results of the ocean bottom seismometer SS, which has large variation in the estimated (calculated) maximum value of the velocity value (PGV). As a result, the earthquake warning issuance device 100 of the first embodiment can more appropriately determine whether or not to issue an earthquake warning AL than earthquake warning issuance devices provided in conventional earthquake early warning systems that use observation results from the ocean-bottom seismometer SS (for example, ocean-bottom seismometer information) to determine whether or not to issue an earthquake warning AL (issue an S-wave warning). In other words, the earthquake warning issuance device 100 of the first embodiment can reduce unnecessary stops (halts) of the train T without issuing unnecessary earthquake warnings AL due to variations in the maximum velocity value (PGV) based on the observation results from the ocean-bottom seismometer SS (ocean-bottom seismometer information). As a result, the earthquake early warning system provided with the earthquake warning issuance device 100 of the first embodiment can improve the reliability and accuracy of control over the issuance of earthquake warnings AL, and can quickly issue an earthquake warning AL when an earthquake E occurs.

[0072] (Second embodiment) The earthquake warning issuance device 100 of the first embodiment controls the issuance of an earthquake warning AL by determining whether or not to issue an earthquake warning AL based on pre-set earthquake warning thresholds (earthquake warning threshold TV and earthquake warning threshold TW). The earthquake warning issuance device of the second embodiment (hereinafter referred to as "earthquake warning issuance device 200") estimates (calculates) the earthquake specifications of the earthquake E that has occurred based on both the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS and the ocean-bottom pressure gauge information observed by the ocean-bottom pressure gauge SW, and controls the issuance of an earthquake warning AL based on the estimated (calculated) earthquake specifications. The earthquake specifications include, for example, the location of the epicenter (geographical location such as latitude, longitude, and depth) and the earthquake scale (magnitude).

[0073] More specifically, the earthquake warning issuing device 200 determines the arrival times of the P waves and S waves of the earthquake E that has occurred based on the ocean bottom seismometer information observed by the ocean bottom seismometer SS and the ocean bottom pressure gauge information observed by the ocean bottom pressure gauge SW, and estimates (calculates) the distance (epicenter distance) between the epicenter of the earthquake E and the position of each observation device OB (position of the observation point) based on the difference between the arrival times. The earthquake warning issuing device 200 may also estimate (calculate) the distance between the epicenter of the earthquake E and the position of the track R on which the train T runs as the epicenter distance. The earthquake warning issuing device 200 then estimates (calculates) the magnitude M of the earthquake E using, for example, a distance attenuation formula for magnitude estimation that includes the earthquake's epicenter distance, magnitude, seismic activity index value, etc. The seismic activity index value is, for example, the maximum velocity value, the maximum acceleration value, the maximum water pressure change index value, etc. The earthquake warning issuing device 200 controls the issuing of an earthquake warning AL based on the estimated (calculated) magnitude M.

[0074] Here, we will explain how the earthquake warning issuing device 200 estimates (calculates) the magnitude M. In the following explanation, we will explain how the earthquake warning issuing device 200 estimates (calculates) the magnitude M of the earthquake E that has occurred based on seabed pressure gauge information observed by the seabed pressure gauges SW provided in each observation device OB arranged in the seafloor observation network NW. The earthquake warning issuing device 200 estimates (calculates) the magnitude M of the earthquake E that has occurred using the following procedure.

[0075] (Magnitude estimation procedure 1): First, the earthquake warning issuing device 200 sequentially (in real time) determines the arrival times of the P waves and S waves in the seismic waves W caused by the earthquake E that has occurred for each position (observation point) of each observation device OB based on the water pressure change index value represented by the seabed pressure gauge information observed by each seabed pressure gauge SW. The earthquake warning issuing device 200 determines the arrival times of the P waves and S waves based on, for example, the water pressure change index value represented by the seabed pressure gauge information.

[0076] (Magnitude Estimation Procedure 2): Next, the earthquake warning issuing device 200 estimates (calculates) the epicenter distance between the epicenter of earthquake E and the position (observation point) of each observation device OB based on the difference between the determined arrival times of the P waves and the S waves. The earthquake warning issuing device 200 estimates (calculates) the epicenter distance by, for example, sequentially (in real time) calculating the STA (Short Term Average) and the LTA (Long Term Average) based on the arrival times of the P waves and the S waves, and sequentially calculating the ratio of the calculated STA to the LTA (=STA / LTA). The method for estimating (calculating) the epicenter distance in the earthquake warning issuing device 200 is not limited to the method using the ratio of STA to LTA (=STA / LTA) described above, and any method may be used.

[0077] (Magnitude Estimation Procedure 3): Next, the earthquake warning issuing device 200 estimates (calculates) the magnitude M of earthquake E for each position (observation point) of each observation device OB using a distance attenuation formula for magnitude estimation prepared in advance. This distance attenuation formula for magnitude estimation is a formula that is predefined, for example, by accumulating in advance bottom water pressure gauge information from when a past earthquake E was observed by a bottom water pressure gauge SW, and calculating using a water pressure change index value based on the water pressure values ​​represented by this accumulated bottom water pressure gauge information. More specifically, the earthquake warning issuing device 200 estimates (calculates) the magnitude M for each observation point by substituting the epicenter distance estimated (calculated) using magnitude estimation procedure 2 and the seismic motion index value (e.g., the maximum value of the water pressure change index value) into the following formula (1) prepared in advance for each installation position (observation point) of each observation device OB.

[0078]

number

[0079] In the above equation (1), M is the magnitude, Δ is the epicenter distance, and γ is a correction term. In the above equation (1), "Pa·s" is the water pressure change index value estimated (calculated) from the water pressure value indicated by the ocean bottom pressure gauge information. For example, "Pa·s" is the water pressure change index value obtained by integrating the water pressure value indicated by the ocean bottom pressure gauge information once in the time domain and then filtering it with a high-pass filter.

[0080] The magnitude M estimated (calculated) in the magnitude estimation procedure 3 is an earthquake parameter that indicates the scale of the earthquake E that occurred.

[0081] The distance attenuation formula for magnitude estimation is an example of the "third distance attenuation formula."

[0082] Through this procedure (magnitude estimation procedure), the earthquake warning issuing device 200 estimates (calculates) the magnitude M of the earthquake E that has occurred based on the bottom water pressure gauge information observed by the bottom water pressure gauge SW.

[0083] As a result, the earthquake warning issuing device 200 can determine, at least based on the magnitude M estimated (calculated) by the magnitude estimation procedure 3, whether the earthquake E that has occurred this time is of a magnitude that requires the issuance of an earthquake warning AL to stop the train T.

[0084] Similarly, the earthquake warning issuing device 200 estimates (calculates) the magnitude M of the earthquake E that has occurred based on the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS. The procedure for estimating the magnitude M based on the ocean-bottom seismometer information in the earthquake warning issuing device 200 can be easily thought of based on the magnitude estimation procedure described above. In this case, the distance attenuation formula for magnitude estimation used in magnitude estimation procedure 3 (the distance attenuation formula corresponding to the water pressure change index value) can be replaced with a distance attenuation formula corresponding to the maximum velocity value or the maximum acceleration value. Therefore, a detailed explanation of the procedure and method by which the earthquake warning issuing device 200 estimates (calculates) the magnitude M based on the ocean-bottom seismometer information observed by the ocean-bottom seismometer SS will be omitted.

[0085] [Example of the configuration of an earthquake warning device] Next, an example of the configuration of the earthquake warning issuance device 200 will be described. FIG. 8 is a diagram showing an example of the configuration of the earthquake warning issuance device 200 according to the second embodiment. The components and functions of the earthquake warning issuance device 200 include the same components and functions as those of the earthquake warning issuance device 100 of the first embodiment. In the following description, the components and functions of the earthquake warning issuance device 200 that are the same as those of the earthquake warning issuance device 100 will be given the same reference numerals, and detailed description of each component and function will be omitted. The earthquake warning issuance device 200 includes, for example, a memory unit 110 and a processing circuit 220.

[0086] The memory unit 110 stores distance attenuation formulas for magnitude estimation (including a distance attenuation formula corresponding to a water pressure change index value and a distance attenuation formula corresponding to a maximum velocity value or a maximum acceleration value) that have been prepared (calculated) in advance. In the following description, the distance attenuation formula for magnitude estimation corresponding to a water pressure change index value is referred to as the "water pressure change index value-corresponding distance attenuation formula," and the distance attenuation formula for magnitude estimation corresponding to a maximum velocity value or a maximum acceleration value is referred to as the "speed-corresponding distance attenuation formula." The memory unit 110 stores, for example, the magnitude (i.e., the magnitude threshold value) of an earthquake E that may cause damage to the train T and that requires the issuance of an earthquake warning AL. The memory unit 110 may also store data and information used by each function in the processing circuit 220 of the earthquake warning issuing device 200 when performing processing.

[0087] The processing circuit 220 executes processes such as an ocean-bottom seismometer information acquisition function 121, a maximum value calculation function 122, a magnitude estimation function 226, an ocean-bottom water pressure gauge information acquisition function 123, a water pressure value integration function 124, a magnitude estimation function 227, and an earthquake warning issuance function 225. Like the processing circuit 120 provided in the earthquake warning issuance device 100, the processing circuit 220 also realizes each function by, for example, a hardware processor executing a program (software) stored in a memory (not shown) (which may be the storage unit 110). The memory (not shown) is realized by, for example, a semiconductor memory element such as a ROM, RAM, or flash memory, a hard disk drive (HDD), an optical disk, or the like.

[0088] The ocean-bottom seismometer information acquisition function 121 sequentially outputs the acquired ocean-bottom seismometer information to the maximum value calculation function 122 and the magnitude estimation function 226. The maximum value calculation function 122 sequentially outputs the estimated (calculated) maximum value of velocity (PGV) (which may be the maximum value of acceleration (PGA)) to the magnitude estimation function 226.

[0089] The magnitude estimation function 226 estimates (calculates) the magnitude M based on the velocity values ​​at each observation point using a distance attenuation formula (velocity-dependent distance attenuation formula) for magnitude estimation stored in the storage unit 110. The magnitude estimation function 226 estimates (calculates) the magnitude M based on the velocity values ​​using a procedure similar to the magnitude estimation procedure described above. More specifically, the magnitude estimation function 226 estimates (calculates) the magnitude M based on the velocity values ​​by substituting the ocean-bottom seismometer information sequentially output by the ocean-bottom seismometer information acquisition function 121 and the maximum velocity values ​​(PGV) (which may be maximum acceleration values ​​(PGA)) sequentially output by the maximum value calculation function 122 into the velocity-dependent distance attenuation formula stored in the storage unit 110. The magnitude estimation function 226 sequentially outputs the magnitude M based on the estimated (calculated) velocity values ​​to the earthquake warning issuance function 225.

[0090] The magnitude estimation function 226 may be configured to store the magnitude M based on the estimated velocity value in the storage unit 110, notify the earthquake warning issuance function 225 that the magnitude M based on the velocity value has been stored, and the earthquake warning issuance function 225 may read the magnitude M based on the velocity value stored in the storage unit 110, thereby outputting the magnitude M based on the estimated velocity value to the earthquake warning issuance function 225. In this case, the magnitude estimation function 226 may be configured to store the magnitude M based on the estimated velocity value in a predetermined storage area allocated in the storage unit 110, and delete the magnitude M based on the velocity value that was stored after the current earthquake E has subsided, thereby always storing the magnitude M based on the velocity value only when an earthquake E has occurred.

[0091] The bottom water pressure gauge information acquisition function 123 sequentially outputs the acquired bottom water pressure gauge information to the water pressure value integration function 124 and the magnitude estimation function 227. The water pressure value integration function 124 sequentially outputs the estimated (calculated) water pressure change index value to the magnitude estimation function 227.

[0092] The magnitude estimation function 227 estimates (calculates) the magnitude M based on the water pressure change index value at each observation point using a distance attenuation formula for magnitude estimation (distance attenuation formula corresponding to water pressure change index value) stored in the memory unit 110. The magnitude estimation function 227 estimates (calculates) the magnitude M based on the water pressure change index value by the magnitude estimation procedure described above. More specifically, the magnitude estimation function 227 estimates (calculates) the magnitude M based on the water pressure change index value by substituting the bottom water pressure gauge information sequentially output by the bottom water pressure gauge information acquisition function 123 and the water pressure change index value sequentially output by the water pressure value integration function 124 into the distance attenuation formula corresponding to water pressure change index value stored in the memory unit 110. The magnitude estimation function 227 sequentially outputs the magnitude M based on the estimated (calculated) water pressure change index value to the earthquake warning issuance function 225.

[0093] The magnitude estimation function 227 may be configured to store the magnitude M based on the estimated water pressure change index value in the memory unit 110, notify the earthquake warning issuance function 225 that the magnitude M based on the water pressure change index value has been stored, and the earthquake warning issuance function 225 may read the magnitude M based on the water pressure change index value stored in the memory unit 110, thereby outputting the magnitude M based on the estimated water pressure change index value to the earthquake warning issuance function 225. In this case, the magnitude estimation function 227 may be configured to store the magnitude M based on the estimated water pressure change index value in a predetermined memory area allocated to the memory unit 110, and delete the stored magnitude M based on the water pressure change index value after the current earthquake E has subsided, thereby always storing the magnitude M based on the water pressure change index value only when an earthquake E has occurred.

[0094] The magnitude estimation function 227 is an example of a function that "determines the arrival time of P waves and the arrival time of S waves due to an earthquake," "estimates the epicenter distance between the observation point and the epicenter of the earthquake based on the difference between the arrival time of the P waves and the arrival time of the S waves," and "estimates the earthquake scale of the earthquake based on the index value of water pressure change, the epicenter distance, and a predefined third distance attenuation formula." The magnitude estimation function 227 is an example of an "estimation unit."

[0095] The earthquake warning issuance function 225 determines whether or not it is necessary to issue an earthquake warning AL to stop the train T, based on the magnitude M based on the velocity values ​​sequentially output by the magnitude estimation function 226 and the magnitude M based on the water pressure change index value sequentially output by the magnitude estimation function 227. At this time, the earthquake warning issuance function 225 determines whether or not each of the magnitude M based on the velocity values ​​sequentially output by the magnitude estimation function 226 and the magnitude M based on the water pressure change index value sequentially output by the magnitude estimation function 227 is equal to or greater than the magnitude threshold stored in the memory unit 110. Then, the earthquake warning issuance function 225 determines that it is necessary to issue an earthquake warning AL when both the magnitude M based on the velocity values ​​and the magnitude M based on the water pressure values ​​are equal to or greater than the magnitude threshold.

[0096] Similar to the earthquake warning issuance function 125 provided in the processing circuit 120 of the earthquake warning issuance device 100, the earthquake warning issuance function 225 may determine whether or not it is necessary to issue an earthquake warning AL to stop the train T, based on the maximum value of the velocity values ​​(PGV) (which may be the maximum value of the acceleration values ​​(PGA)) sequentially output by the maximum value calculation function 122 and the water pressure change index value sequentially output by the water pressure value integration function 124. In this case, the earthquake warning issuance function 225 may switch between the determination result of whether or not the maximum value of the velocity values ​​(PGV) exceeds the earthquake warning threshold TV for the velocity values ​​and the determination result of whether or not the water pressure change index value exceeds the earthquake warning threshold TW, based on either or both of the magnitude M based on the velocity values ​​and the magnitude M based on the water pressure values, to determine whether or not it is necessary to issue an earthquake warning AL.

[0097] The earthquake warning issuance function 225 actually issues an earthquake warning AL when it determines that an earthquake warning AL needs to be issued, which allows the driver of the train T for which an earthquake warning AL has been issued to safely stop (halt) the train T.

[0098] The earthquake warning issuance function 225 is an example of a function that "controls the issuance of earthquake warnings." The earthquake warning issuance function 225 is an example of an "earthquake warning issuing unit." The magnitude threshold is an example of an "earthquake scale threshold."

[0099] [Earthquake warning issuance control in earthquake warning issuing devices] Next, an example of the process in which the earthquake warning issuance device 200 issues an earthquake warning AL based on information (data) about an earthquake E output by each observation device OB arranged in the seafloor observation network NW will be described. More specifically, an example of the process in which the earthquake warning issuance device 200 issues an earthquake warning AL based on the magnitude M estimated (calculated) from the ocean-bottom seismometer information output by the ocean-bottom seismometer SS and the ocean-bottom pressure gauge information output by the ocean-bottom pressure gauge SW will be described. Figure 9 is a flowchart showing an example of the process flow in which the earthquake warning issuance device 200 according to the second embodiment issues an earthquake warning AL. The processes in this flowchart are also repeatedly executed in the earthquake warning issuance device 200 while the earthquake early warning system is operating. In the following explanation, for ease of explanation, it is assumed that the observation device OB outputs information (data) regarding earthquake E, and the earthquake warning issuing device 200 controls the issuance of an earthquake warning AL based on the seafloor seismometer information output by the seafloor seismometer SS equipped in the observation device OB and the seafloor water pressure gauge information output by the seafloor water pressure gauge SW.

[0100] The flowchart shown in Fig. 9 includes processing similar to the processing for issuing an earthquake warning AL in the earthquake warning issuance device 100 shown in Fig. 7. Therefore, in the flowchart shown in Fig. 9, the same processing as in the flowchart shown in Fig. 7 is given the same step number, and detailed explanations thereof will be omitted.

[0101] In the processing of steps S100 and S102, the processing circuit 220 estimates (calculates) the maximum velocity value (PGV) for each observation point (each observation device OB) based on the ocean-bottom seismometer information observed and output by the ocean-bottom seismometer SS equipped in each observation device OB arranged in the ocean-bottom observation network NW. Similar to the processing circuit 120 equipped in the earthquake warning issuing device 100, the processing circuit 220 may estimate (calculate) the maximum acceleration value (PGA) for each observation point (each observation device OB).

[0102] Then, the processing circuit 220 executes the magnitude estimation function 226 to estimate (calculate) the magnitude M of the earthquake E that has occurred based on the velocity values ​​(which may be acceleration values) indicated by the acquired ocean-bottom seismometer information, for each position (observation point) of each observation device OB (step S200). The processing circuit 220 continues to acquire the ocean-bottom seismometer information in step S100, estimate (calculate) the maximum velocity value (PGV) in step S102, and estimate (calculate) the magnitude M in step S200 during the subsequent processing.

[0103] Furthermore, in the processing of steps S110 and S112, the processing circuit 220 estimates (calculates) a water pressure change index value for each observation point (each observation device OB) based on the seabed water pressure gauge information observed and output by the seabed water pressure gauge SW equipped on each observation device OB located in the seabed observation network NW.

[0104] Then, the processing circuit 220 executes the magnitude estimation function 227 to estimate (calculate) the magnitude M of the earthquake E that has occurred based on the water pressure change index value indicated by the acquired seabed water pressure gauge information, for each position (observation point) of each observation device OB (step S210). The processing circuit 220 continues to acquire the seabed water pressure gauge information in step S110, integrate and filter the water pressure values ​​(estimate (calculate) the water pressure change index value) in step S112, and estimate (calculate) the magnitude M in step S210 during subsequent processing.

[0105] In the processing flowchart of the earthquake warning issuance device 200 shown in Fig. 9, as in the flowchart shown in Fig. 7, if the processing of step S102 is performed after the processing of step S100, and the processing of step S112 is performed after the processing of step S110, the estimation (calculation) of the maximum velocity value (PGV) and the estimation (calculation) of the water pressure change index value may be performed simultaneously or in reverse. Furthermore, the processing flowchart of the processing of the earthquake warning issuance device 200 shown in Fig. 9 shows an example in which the estimation (calculation) of the magnitude M based on the velocity value by the processing of step S200 and the estimation (calculation) of the magnitude M based on the water pressure change index value by the processing of step S210 are performed in this order, but the processing of step S200 and the processing of step S210 are not limited to this order and may be performed simultaneously or in reverse, for example.

[0106] The processing circuit 220 executes the earthquake warning issuance function 225 and determines whether or not an earthquake warning AL needs to be issued based on the magnitude M based on the velocity value estimated (calculated) by the processing of step S200 and the magnitude M based on the water pressure change index value estimated (calculated) by the processing of step S210 (step S220). That is, the processing circuit 220 determines whether or not to stop the train T in response to the currently occurring earthquake E based on the respective magnitudes M estimated (calculated) in steps S200 and S210. At this time, the processing circuit 220 determines, for example, whether or not each estimated (calculated) magnitude M is equal to an earthquake scale=magnitude that is predetermined as an earthquake E that may cause damage to the train T, and determines whether or not to stop the train T based on the determination result.

[0107] If it is determined in step S220 that it is not necessary to issue an earthquake alarm AL, the processing circuit 220 returns the process to step S100 and repeats the processes of steps S100 to S220.

[0108] On the other hand, if it is determined in step S220 that an earthquake warning AL needs to be issued, the processing circuit 220 executes the earthquake warning issuance function 225 to issue an earthquake warning AL to, for example, a train T traveling on the track R (step S140). This allows the driver of the train T for which an earthquake warning AL has been issued to safely stop (halt) the train T.

[0109] With such a configuration and processing, the earthquake warning issuance device 200 of the second embodiment estimates (calculates) the magnitude M of the earthquake E that has occurred based on the observation results (ocean bottom seismometer information and ocean bottom pressure gauge information) of the ocean bottom seismometers SS and ocean bottom pressure gauges SW equipped in each observation device OB arranged in the ocean bottom observation network NW. In other words, the earthquake warning issuance device 200 of the second embodiment estimates (calculates) the magnitude M of the earthquake E that has occurred based on the observation results of the ocean bottom seismometers SS, which have a large variance in the estimated (calculated) maximum velocity values ​​(PGV), as well as the observation results of the ocean bottom pressure gauges SW, which have a small variance in the estimated (calculated) maximum water pressure change index values. Then, the earthquake warning issuance device 200 of the second embodiment determines whether or not to issue an earthquake warning AL in response to the earthquake E that has occurred based on the estimated (calculated) magnitude M. As a result, the earthquake warning issuance device 200 of the second embodiment, like the earthquake warning issuance device 100 of the first embodiment, can also reduce unnecessary stopping (halting) of the train T without issuing unnecessary earthquake warnings AL caused by variations in the maximum velocity value (PGV) based on the observation results (ocean bottom seismometer information) from the ocean bottom seismometer SS. As a result, the earthquake early warning system including the earthquake warning issuance device 200 of the second embodiment can also improve the reliability and accuracy of control over the issuance of earthquake warnings AL, like the earthquake early warning system including the earthquake warning issuance device 100 of the first embodiment, and can quickly issue an earthquake warning AL when an earthquake E occurs.

[0110] As described above, the earthquake warning issuing device of each embodiment (earthquake warning issuing device 100 and earthquake warning issuing device 200) controls the issuance of an earthquake warning AL to stop a train T based on the observation results of the ocean-bottom seismometer SS equipped in each observation device OB arranged in the ocean-floor observation network NW and the observation results of the ocean-bottom pressure gauge SW equipped in the same observation device OB. In other words, the earthquake warning issuing device of each embodiment controls the issuance of an earthquake warning AL based on the observation results of the ocean-bottom seismometer SS, which has a large variance in the estimated (calculated) maximum velocity value (PGV), as well as the observation results of the ocean-bottom pressure gauge SW, which has a small variance in the estimated (calculated) maximum water pressure change index value. As a result, an earthquake early warning system equipped with the earthquake warning issuing device of each embodiment can appropriately control the issuance of an earthquake warning AL when an earthquake E occurs, reducing the need to stop (halt) unnecessary trains T and safely stopping (halting) necessary trains T. That is, in the earthquake early warning system equipped with the earthquake warning issuance device of each embodiment, it is possible to improve the reliability and accuracy of the control of the issuance of the earthquake warning AL, and to quickly issue the earthquake warning AL when an earthquake E occurs. As a result, in the earthquake early warning system equipped with the earthquake warning issuance device of each embodiment, it is possible to increase the stability of operation of the train T even when an earthquake E occurs.

[0111] In the above-described embodiments, the earthquake warning issuing device (earthquake warning issuing device 100 and earthquake warning issuing device 200) controls the issuance of an earthquake warning AL to stop a train T based on the observation results of the ocean-bottom seismometer SS equipped in each observation device OB arranged in the seafloor observation network NW and the observation results of the ocean-bottom water pressure gauge SW equipped in the same observation device OB. That is, the earthquake warning issuing device of each embodiment is configured to control the issuance of an earthquake warning AL by combining the observation results of the ocean-bottom seismometer SS and the observation results of the ocean-bottom water pressure gauge SW. However, as described above, the variation in the maximum water pressure change index value based on the observation results of the ocean-bottom water pressure gauge SW is smaller than the variation in the maximum velocity value (PGV) based on the observation results of the ocean-bottom seismometer SS. Therefore, the earthquake warning issuing device of each embodiment is not limited to a configuration that controls the issuance of an earthquake warning AL by combining the observation results of the ocean-bottom seismometer SS and the observation results of the ocean-bottom water pressure gauge SW. For example, the earthquake warning issuing device may control the issuance of an earthquake warning AL based solely on the observation results of the ocean-bottom pressure gauge SW, which has little variance. In this case, the earthquake warning issuing device may omit the components and functions related to the observation results of the ocean-bottom seismometer SS from the components and functions of the earthquake warning issuing device of each of the above-mentioned embodiments. The operation and processing of the earthquake warning issuing device in this case may be equivalent to the operation and processing of the earthquake warning issuing device of each of the above-mentioned embodiments. Therefore, a detailed description of the configuration and operation of the earthquake warning issuing device in a configuration in which the issuance of an earthquake warning AL is controlled solely on the observation results of the ocean-bottom pressure gauge SW will be omitted.

[0112] In the above-described embodiments, the case where the earthquake warning issuing device actually issues an earthquake warning AL to a train T for which an earthquake warning AL needs to be issued has been described. That is, in the above-described embodiments, the case where the earthquake warning issuing device directly issues an earthquake warning AL to the train T has been described. However, the earthquake warning issuing device is not limited to a configuration in which it directly issues an earthquake warning AL to the train T. As described above, for example, the earthquake warning issuing device may issue an earthquake warning AL to a traffic management system that manages the operation of the train T or a power supply facility such as a substation that supplies power for the train T to run, or may output information regarding the earthquake warning AL to be issued. In this case, the control of the issuance of an earthquake warning AL by the earthquake warning issuing device may be equivalent to the control of the issuance of an earthquake warning AL by the earthquake warning issuing device in the above-described embodiments. Therefore, a detailed description of the control of the issuance of an earthquake warning AL by the earthquake warning issuing device in a configuration in which the earthquake warning AL is not directly issued to the train T will be omitted.

[0113] The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment, and various modifications and substitutions can be made within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0114] 100,200 Earthquake warning device 110...Storage section 120,220 Processing circuit 121...Seafloor seismometer information acquisition function 122 Maximum value calculation function 123···Submarine water pressure gauge information acquisition function 124...Water pressure integration function 125 Earthquake warning function 226···Magnitude estimation function 227···Magnitude estimation function 225 Earthquake warning function NW···Seabed Observation Network MS...Land station OB...observation equipment SS...Seafloor seismometer SW...Subsea Pressure Gauge

Claims

1. an integration unit that once integrates water pressure values ​​observed by water pressure meters provided in each of observation devices installed at a plurality of observation points on a submarine cable laid on the seabed, and then performs filtering using a high-pass filter of a predetermined frequency to estimate an index value of water pressure change; an earthquake warning issuing unit that controls the issuance of earthquake warnings based on the index value of the water pressure change; An earthquake warning issuing device equipped with:

2. The earthquake warning issuing unit determining whether the index value of the water pressure change exceeds a preset earthquake warning threshold; When the index value of the water pressure change exceeds the earthquake warning threshold, the earthquake warning is issued. The earthquake warning issuing device according to claim 1.

3. the earthquake warning threshold is calculated based on a second distance attenuation formula defined in advance as a maximum value of the index value of the water pressure change estimated in the event of an earthquake of a magnitude calculated based on measurement data from seismometers installed along the railway and a first distance attenuation formula defined in advance, the first distance attenuation formula is calculated based on acceleration values ​​of seismic motions represented by measurement data of earthquakes that have occurred in the past and is defined in advance; the second distance attenuation equation is calculated based on an index value of a water pressure change of the water pressure gauge that observed earthquakes that occurred in the past, and is defined in advance; The earthquake warning issuing device according to claim 2.

4. an estimation unit that estimates the magnitude of an earthquake that has occurred for each of the observation points based on the index value of the water pressure change; The earthquake warning issuing unit determining whether the magnitude of the earthquake is equal to or greater than a predetermined earthquake magnitude threshold; When the earthquake magnitude is equal to or greater than the earthquake magnitude threshold, the earthquake warning is issued. The earthquake warning issuing device according to claim 1.

5. The estimation unit determining, for each of the observation points, the arrival times of P waves and S waves due to the earthquake based on the index value of the water pressure change; estimating, for each of the observation points, the epicenter distance between each of the observation points and the epicenter of the earthquake based on the difference between the arrival times of the P waves and the S waves; and estimating the magnitude of the earthquake based on the index value of the water pressure change, the epicenter distance, and a predefined third distance attenuation formula. The earthquake warning issuing device according to claim 4.

6. The estimation unit the index value of the water pressure change and the epicenter distance are substituted into the third distance attenuation formula to estimate the magnitude of the earthquake. The earthquake warning issuing device according to claim 5.

7. The earthquake magnitude threshold is the magnitude of an earthquake that may cause damage along a railway line, the third distance attenuation formula is calculated and defined in advance based on the index value of the water pressure change of the water pressure gauge that observed earthquakes that occurred in the past; The earthquake warning issuing device according to claim 6.

8. a water pressure measurement device for measuring the water pressure at a plurality of observation points on a submarine cable installed on the seabed, the water pressure measurement device for measuring the water pressure at a plurality of observation points ... seabed, the water pressure measurement device for measuring the Controlling the issuance of earthquake warnings based on the index value of the water pressure change. How earthquake warnings are issued.

9. On the computer, The water pressure values ​​observed by the water pressure gauges provided in the respective observation devices arranged at a plurality of observation points on the submarine cable laid on the seabed are integrated once, and then a water pressure index value is estimated by filtering the values ​​using a high-pass filter of a predetermined frequency; Controlling the issuance of earthquake warnings based on the index value of the water pressure change. program.

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