Earthquake warning issuing method, earthquake warning issuing device, and program

Abstract

To provide an earthquake warning issuing method, an earthquake warning issuing device, and a program capable of issuing an earthquake warning with immediacy and high reliability on the basis of seismic waves obtained by measuring an occurred earthquake at a plurality of locations.SOLUTION: An earthquake warning issuing method causes a computer to: detect, for each of a plurality of measurement points provided on an optical fiber cable installed along a railway line, an arrival time of a P wave caused by an occurred earthquake on the basis of measurement data measured at the respective measurement points; determine a hypocenter of the earthquake for each measurement point on the basis of the arrival time of the P wave; estimate a hypocentral distance between the respective measurement point and the corresponding hypocenter for each measurement point; calculate, for each measurement point, a seismic motion index value based on the P wave on the basis of the measurement data; estimate a seismic magnitude of the earthquake for each measurement point on the basis of a predefined regression expression, the hypocentral distance, and the seismic motion index value; and control the issuance of an earthquake warning on the basis of the hypocentral distance and the seismic magnitude.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] To ensure the safety of running trains, it is necessary to detect earthquakes early and, if necessary, stop trains. For this reason, earthquake early warning systems have traditionally been used to detect earthquakes early and issue earthquake warnings to stop running trains. Conventional earthquake early warning systems issue earthquake warnings when a single seismometer detects seismic waves generated by an earthquake, in order to quickly stop trains when an earthquake occurs. In other words, conventional earthquake early warning systems issue earthquake warnings based on seismic waves observed at a single observation point. Furthermore, when a seismometer detects primary waves (P waves), which arrive before secondary waves (S waves), the main motion of an earthquake, the system uses the initial arrival of the P waves (information immediately after the arrival of the P waves) to estimate the earthquake characteristics (e.g., the location of the epicenter and the magnitude of the earthquake) of the earthquake. The system then issues an earthquake warning based on these estimated earthquake characteristics, thereby speeding up train operation control in the event of an earthquake.

[0003] However, even when using the initial arrival of P waves to estimate earthquake parameters, issuing earthquake warnings using a single observation point offers the advantage of issuing earthquake warnings quickly based on seismic waves detected by a seismometer. However, since the earthquake parameters are estimated based on seismic waves detected by a single seismometer, the estimation relies on a single piece of information, resulting in a large error in the estimated earthquake parameters. Therefore, increasing the number of observation points is considered a way to reduce the error in the estimated earthquake parameters, i.e., to improve the accuracy of the estimated earthquake parameters. However, currently, seismometers are installed every few dozen kilometers along railway lines, and increasing the number of seismometers to increase the number of observation points is not practical from the perspective of running costs, etc. Furthermore, although issuing earthquake warnings using multiple observation points can estimate earthquake parameters more accurately than issuing earthquake warnings using a single observation point, the need for seismic waves to be detected by seismometers at multiple points compromises the immediacy of the warnings.

[0004] In recent years, a measurement technology called Distributed Acoustic Sensing (DAS) using optical fiber cables has been developed and is beginning to spread. DAS is a technology that uses optical fiber cables to measure strain. By measuring strain every few meters along the optical fiber cable, it is possible to measure strain caused by vibrations associated with the movement of a train and accurately determine the train's running position. For example, Patent Document 1 proposes using DAS technology to measure seismic motion caused by an earthquake. Moreover, in recent years, optical fiber cables for communication purposes have sometimes been laid along railway tracks. For this reason, it would be more desirable to be able to issue earthquake warnings by estimating earthquake parameters from seismic waves measured at multiple locations using DAS technology. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-100442 Summary of the Invention [Problem to be solved by the invention]

[0006] However, no conventional technology has been proposed for estimating earthquake parameters using DAS technology. For this reason, it is considered difficult to estimate earthquake parameters from high-density seismic motion (seismic waves from multiple locations) measured using DAS technology, or to issue early earthquake warnings based on the estimated earthquake parameters, using the conventional technology.

[0007] The present invention has been made based on the recognition of the above-mentioned problems, and aims to provide an earthquake warning issuing method, an earthquake warning issuing device, and a program that can issue an earthquake warning that is immediate and highly reliable based on seismic waves measured at multiple points when an earthquake occurs. [Means for solving the problem]

[0008] The earthquake warning issuing method, earthquake warning issuing device, and program according to the present invention employ the following configuration. (1): An earthquake warning issuance method according to one embodiment of the present invention is an earthquake warning issuance method in which a computer detects, for each of a plurality of measurement points provided on an optical fiber cable installed along a railway line, the arrival time of a P wave from an earthquake that has occurred, based on measurement data measured at the measurement points; determines, for each of the measurement points, the epicenter of the earthquake, based on the arrival time of the P wave; estimates, for each of the measurement points, the epicenter distance between the measurement point and the corresponding epicenter; calculates, for each of the measurement points, a seismic motion index value based on the P wave, based on the measurement data; estimates, for each of the measurement points, the magnitude of the earthquake, based on a predefined regression equation, the epicenter distance, and the seismic motion index value; and controls the issuance of an earthquake warning, based on the epicenter distance and the earthquake magnitude.

[0009] (2): In the above aspect (1), the computer controls the issuance of the earthquake warning based on the epicenter distance and the earthquake magnitude obtained by performing statistical processing on the earthquake magnitude corresponding to each of the measurement points.

[0010] (3): In the above aspect (2), the regression equation is calculated based on measurement data obtained by measuring earthquakes that occurred in the past at a plurality of the measurement points, and is defined in advance.

[0011] (4) In the above aspect (3), the seismic index value is calculated by detecting the arrival time of an S wave from an earthquake that has occurred for each of the measurement points based on the measurement data.

[0012] (5): In the above aspect (4), the computer estimates the magnitude of the earthquake by substituting the epicenter distance and the seismic motion index value into the regression equation.

[0013] (6): In the above aspect (5), when the number of measurement points that detected the arrival time of the P wave exceeds the first detection number, the computer determines the epicenter at the measurement point that detected the arrival time of the P wave, estimates the epicenter distance at the measurement point that detected the arrival time of the P wave, calculates the seismic motion index value at the measurement point that detected the arrival time of the P wave, and estimates the earthquake magnitude at the measurement point that detected the arrival time of the P wave.

[0014] (7): In the above aspect (6), when the number of measurement points at which the arrival time of the P wave is detected increases by a predetermined number or more, the computer determines the epicenter at the increased measurement point, estimates the epicenter distance at the increased measurement point, calculates the seismic motion index value at the increased measurement point, estimates the earthquake magnitude at the increased measurement point, and controls the issuance of the earthquake warning, including the epicenter distance at the increased measurement point and the earthquake magnitude.

[0015] (8): An earthquake warning issuance device according to one embodiment of the present invention is an earthquake warning issuance device that includes: a P-wave arrival detection unit that detects the arrival time of P-waves from an earthquake that has occurred for each measurement point based on measurement data measured at multiple measurement points provided on an optical fiber cable installed along a railway line; an epicenter determination unit that determines the epicenter of the earthquake for each measurement point based on the arrival time of the P-waves; an epicenter distance estimation unit that estimates the epicenter distance between each measurement point and the corresponding epicenter for each measurement point; a seismic activity index value calculation unit that calculates a seismic activity index value based on the P-waves for each measurement point based on the measurement data; an earthquake magnitude estimation unit that estimates the magnitude of the earthquake for each measurement point based on a predefined regression equation, the epicenter distance, and the seismic activity index value; and an earthquake warning issuance unit that controls the issuance of an earthquake warning based on the epicenter distance and the earthquake magnitude.

[0016] (9): A program according to one embodiment of the present invention is a program that causes a computer to detect, for each of a plurality of measurement points on an optical fiber cable installed along a railway line, the arrival time of P waves from an earthquake that has occurred, based on measurement data measured at the measurement points; determine, for each of the measurement points, the epicenter of the earthquake, based on the arrival time of the P waves; estimate, for each of the measurement points, the epicenter distance between the measurement point and the corresponding epicenter; calculate, for each of the measurement points, a seismic activity index value based on the P waves, based on the measurement data; estimate, for each of the measurement points, the magnitude of the earthquake, based on a predefined regression equation, the epicenter distance, and the seismic activity index value; and control the issuance of an earthquake warning, based on the epicenter distance and the earthquake magnitude. [Effects of the Invention]

[0017] According to the present invention, it is possible to issue an earthquake warning that is immediate and highly reliable based on seismic waves measured at multiple points when an earthquake occurs. [Brief explanation of the drawings]

[0018] [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. 10 is a diagram showing an example of measurement results measured in each measurement channel of the DAS system. [Figure 3] 10 is a flowchart showing an example of a process flow for issuing an earthquake warning in an earthquake warning issuing device. [Figure 4] FIG. 1 is a diagram illustrating an example of the configuration of an earthquake warning issuing device. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of an earthquake warning issuing method, an earthquake warning issuing device, and a program according to the present invention will be described with reference to the drawings.

[0020] [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.

[0021] In an earthquake early warning system, an earthquake warning issuing device 100 estimates earthquake specifications of an earthquake E that has occurred based on measurement results RC of each measurement channel C of a distributed acoustic sensing (DAS) system using optical fiber cables. The earthquake specifications include, for example, the location of the epicenter (geographical location such as latitude, longitude, and depth) and the scale of the earthquake (earthquake scale = magnitude). The optical fiber cables are installed, for example, along railway tracks to carry communications related to the operation of trains T. The optical fiber cables are laid, for example, along tracks R for a length of several tens of kilometers or more. In the distributed acoustic sensing system (hereinafter referred to as a "DAS system"), each of the multiple measurement channels C is set, for example, at intervals of several meters (e.g., 5 meters). In the DAS system, each measurement channel C measures the phase difference of scattered light when scattered by scatterers (glass) inside the optical fiber cable, thereby sequentially measuring the strain associated with seismic motion caused by the seismic waves W of the earthquake E that has occurred, and sequentially (in real time) outputs the measurement results RC representing this measured strain to the earthquake warning issuing device 100. This allows the earthquake warning issuing device 100 to estimate the earthquake parameters of the earthquake E that has occurred with higher accuracy based on the measurement results RC of each measurement channel C.

[0022] The seismic waves W that represent the seismic motion caused by earthquake E include P waves (primary waves), which are the first to arrive, vibrating in the direction of the seismic wave's propagation and causing vertical movement of the ground (so-called vertical shaking), and S waves (secondary waves), which are the second to arrive, vibrating perpendicular to the direction of the seismic wave's propagation and are the main cause of horizontal movement of the ground (so-called horizontal shaking).For this reason, the measurement results RC output by each measurement channel C of the DAS system contain information on both the P waves and the S waves.

[0023] Furthermore, the measurement results RC output by each measurement channel C in the DAS system include not only information representing the seismic motion of the earthquake E described above, but also vibrations caused by the running of the train T. The earthquake warning issuing device 100 may be configured to ascertain the current running position of the train T running on the track R (hereinafter referred to as "train running position") based on the measurement results RC output by each measurement channel C.

[0024] The DAS system has the same configuration as existing distributed acoustic sensing systems, so we will not provide detailed explanations of the DAS system configuration, the method for measuring the phase difference of scattered light, the method for measuring distortion, or the data structure of the output measurement results RC.

[0025] Here, we will explain an example of seismic motion caused by earthquake E measured by a DAS system. Figure 2 shows an example of measurement results RC measured by each measurement channel C of the DAS system. Figure 2(a) schematically illustrates an example of a state in which a train T is running. Figure 2(b) shows an example in which the vertical axis represents each measurement channel C (channels 1 to 12000) of the DAS system, and the horizontal axis represents the magnitude (amount of strain) of the measurement results RC output by each measurement channel C, i.e., the magnitude of seismic motion caused by earthquake E (including vibrations associated with the movement of train T) and its temporal change. The vertical axis in Figure 2(b) can be converted to distance by multiplying it by the interval at which each measurement channel C is set. More specifically, if the measurement channels C are set at 5-meter intervals, the distance from measurement channel C of channel 1 to channel 12000 on the vertical axis shown in Figure 2(b) can be converted to a distance of 60 km.

[0026] FIG. 2(b) shows the time it takes for the P-waves and S-waves from the seismic wave W of the earthquake E to reach each measurement channel C. Furthermore, FIG. 2(b) also shows the train T's travel path, which indicates the change in train position as the train T travels through each measurement channel C. The earthquake warning issuing device 100 estimates the earthquake parameters of the earthquake E based on the information on the P-waves and S-waves represented by the measurement results RC output by each measurement channel C. The earthquake warning issuing device 100 can estimate the location of the epicenter of the earthquake E and the distance from the epicenter (i.e., the epicenter distance) from, for example, the difference in arrival times of P-waves (or S-waves) measured by adjacent measurement channels C or measurement channels C separated by a predetermined distance as shown in FIG. 2(b). The earthquake warning issuing device 100 can estimate the depth of the epicenter of the earthquake E from, for example, the difference in arrival times of P-waves and S-waves in the same measurement channel C as shown in FIG. 2(b). The earthquake warning issuing device 100 can estimate the magnitude of the earthquake E that has occurred, for example, from the magnitude (amount of distortion) of the P waves (or S waves) measured by the same measurement channel C shown in (b) of Figure 2.

[0027] The measurement channel C is an example of a "measurement point." The measurement result RC is an example of "measurement data."

[0028] The earthquake warning issuance device 100 may estimate the earthquake parameters of the earthquake E that has occurred based on information about the seismic waves W detected by the seismometer, in addition to information about the seismic waves W represented in the measurement results RC output by each measurement channel C of the DAS system. FIG. 1 shows one seismometer S. The seismometer S detects seismic motion at, for example, the location where it is installed. The seismometer S may be installed at a location different from each measurement channel C of the DAS system, or may be installed at the same location as any of the measurement channels C. As described above, since the seismic waves W include P waves and S waves, the seismometer S is equipped with a triaxial vibration sensor for detecting each of the P waves and S waves. The vibration sensor included in the seismometer S (hereinafter simply referred to as "seismometer S") sequentially (in real time) outputs information about waveforms (vibration waveforms) representing the detected seismic motion (including information about vibration waveforms representing ground vibrations detected under normal conditions when no earthquake is occurring) to the earthquake warning issuance device 100. In the following description, the information on the vibration waveform output by the seismometer S will be referred to as the "vibration waveform VW."

[0029] The seismometer S has the same configuration as existing seismometers. Therefore, detailed explanations of the configuration of the seismometer S, the method for detecting seismic motion, the data structure of the output vibration waveform information, etc. will be omitted.

[0030] 1 shows a configuration in which the seismometer S and the earthquake warning issuing device 100 are separate components, that is, a configuration as a system, but the seismometer S and the earthquake warning issuing device 100 may also be integrated into one configuration. The earthquake warning issuing device 100 may also be installed in the same position as any of the measurement channels C.

[0031] Next, we will explain in more detail the method for estimating earthquake parameters in the earthquake warning issuing device 100. First, we will explain the epicenter determination method in which the earthquake warning issuing device 100 determines the epicenter of the earthquake E that has occurred based on the measurement results RC output by each measurement channel C of the DAS system. When determining the epicenter of the earthquake E that has occurred, the earthquake warning issuing device 100 performs the epicenter determination in the following procedure.

[0032] (Epicenter Determination Procedure 1): First, the earthquake warning issuance device 100 detects the arrival of P waves in the seismic waves W caused by the earthquake E at each set position (measurement point) of each measurement channel C based on the amount of strain represented by each measurement result RC. In other words, the earthquake warning issuance device 100 detects the arrival time of P waves at each measurement point. The earthquake warning issuance device 100 detects the arrival of P waves, for example, by sequentially (in real time) calculating the STA (Short Term Average) and LTA (Long Term Average) for the seismic waves W (vibration waveform) from changes in the amount of strain represented by the measurement result RC, and sequentially calculating the ratio of the calculated STA to LTA (= STA / LTA).

[0033] More specifically, the earthquake warning issuing device 100 calculates the STA of the P wave at time k when the seismic motion due to the seismic wave W of the earthquake E is detected by the following formula (1): p (k) is calculated sequentially, and the LTA of the P wave at time k is calculated using the following equation (2). p (k) is calculated sequentially.

[0034]

number

[0035]

number

[0036] In the above equations (1) and (2), x i is the strain (earthquake motion) data (hereinafter referred to as "earthquake motion data") represented by the time-series measurement results RC output in real time by measurement channel C. In the above equations (1) and (2), k is the amount of seismic motion data x i are the times when each of these was detected. p is the STA of the P wave p(k) is the length of the short time period for calculating β in the above formula (2). p is the LTA of the P wave p The length of the long-term time for calculating (k). p and long-term beta p and are set in advance as parameters for the earthquake warning issuing device 100. For example, the short-term α p is 0.5 [seconds], and the long-term β p is 10.0 seconds. p and long-term beta p and are units of time intervals for detecting earthquake motion in the earthquake warning issuing device 100, that is, units of sampling time, and are valid STAs. p (k) and LTA p Any length of time may be used as long as it is possible to determine each of (k) and (k).

[0037] The method for detecting the arrival of P waves (method for detecting seismic motion) in the earthquake warning issuing device 100 is not limited to the method using the ratio of STA to LTA (=STA / LTA) described above, and any method may be used.

[0038] (Epicenter Determination Procedure 2): Next, if the number of measurement channels C that have detected the arrival of P waves in epicenter determination procedure 1 exceeds a predetermined number (hereinafter referred to as the "first detection number"), the earthquake warning issuing device 100 uses a predetermined method to determine the epicenter corresponding to the set position (measurement point) of each measurement channel C. The first detection number of measurement channels C used to determine the epicenter is, for example, 10 channels. This first detection number is not limited to 10 channels and may be changed, for example, depending on the number of measurement channels C that first detected the arrival of P waves. For example, if the epicenter of earthquake E is close, the number of measurement channels C that first detect the arrival of P waves will be small, but if the epicenter of earthquake E is far away, the number of measurement channels C that first detect the arrival of P waves will be large, so the first detection number may be, for example, 100 channels. The method used for determining the epicenter is, for example, a method using multiple measurement points (observation points), such as hypomh (a method for determining the epicenter using maximum likelihood estimation: Hirata and Matsu'ura, 1987). The method used for determining the epicenter is not limited to the method using hypomh described above, and any method may be used.

[0039] (Epicenter Determination Procedure 3): Next, the earthquake warning issuing device 100 estimates (calculates) the distance (epicenter distance) between the setting position of each measurement channel C, i.e., the position of the track R on which the train T runs, and the epicenter, based on the epicenter corresponding to the setting position (measurement point) of each measurement channel C determined in epicenter determination procedure 2. The epicenter distance estimated (calculated) in epicenter determination procedure 3 is an earthquake parameter that represents the position of the epicenter of the earthquake E that has occurred. Examples of methods used to calculate the epicenter distance include the Vincentry method, which uses a method of calculating (approximating) the distance between two points assuming the earth is a spheroid. The method used to calculate the epicenter distance is not limited to the method using the Vincentry method described above, and any method may be used.

[0040] (Epicenter Determination Procedure 4): Thereafter, when the number of measurement channels C that have detected the arrival of P waves in epicenter determination procedure 1 increases by a predetermined number (hereinafter referred to as the "increase number"), the earthquake warning issuance device 100 determines the epicenter corresponding to the set position (measurement point) of each measurement channel C, as in epicenter determination procedure 2. That is, in epicenter determination procedure 4, the earthquake warning issuance device 100 recalculates the epicenter determination corresponding to the set position (measurement point) of each measurement channel C. The increase in the number of measurement channels C for which the epicenter determination is recalculated is, for example, 10 channels. This increase is not limited to 10 channels, and may be changed, for example, depending on the number of measurement channels C that first detected the arrival of P waves, or depending on the elapsed time since the first detection of the arrival of P waves. The earthquake warning issuance device 100 then estimates (calculates) the epicenter distance based on the recalculated epicenters corresponding to the set positions (measurement points) of each measurement channel C. That is, in epicenter determination procedure 4, the earthquake warning issuance device 100 estimates (calculates) the epicenter distance between the epicenter and the setting position of each newly determined measurement channel C, as in epicenter determination procedure 3. The recalculation of epicenter determination and estimation of epicenter distance in the earthquake warning issuance device 100 may be repeated, for example, until the number of measurement channels C that detected the arrival of P waves reaches a predetermined number (hereinafter referred to as the "second detection number") or may be repeated a predetermined number of times. The second detection number is, for example, 300 channels. This second detection number is not limited to 300 channels and may be changed depending on, for example, the number of measurement channels C that first detected the arrival of P waves, or a number that is considered to enable the earthquake warning issuance device 100 to perform epicenter determination and epicenter distance estimation with higher accuracy.

[0041] By using this procedure (epicenter determination procedure), the earthquake warning issuing device 100 improves the accuracy of the estimated (calculated) epicenter distance.

[0042] Next, we will explain the magnitude estimation method used by the earthquake warning issuing device 100 to estimate the scale of the earthquake E that has occurred based on the measurement results RC output by each measurement channel C of the DAS system. When estimating the magnitude of the earthquake E that has occurred, the earthquake warning issuing device 100 performs the magnitude estimation using the following procedure.

[0043] (Magnitude Estimation Procedure 1): As a preliminary step, an empirically determined relational equation (regression equation) such as the following equation (3) is defined in advance. This regression equation is calculated, for example, by continuously measuring earthquakes using a DAS system to accumulate measurement results RC in advance, and then using the strain amount (seismic motion data) represented by these accumulated measurement results RC. In other words, the regression equation is calculated and defined based on the measurement results RC of earthquakes E that occurred in the past measured using a DAS system. The regression equation includes, for example, the earthquake's epicenter distance, magnitude, and seismic motion index value. The seismic motion index value is, for example, the maximum P-wave strain velocity.

[0044]

number

[0045] In the above equation (3), E i is the seismic index value, M is the magnitude, and D i is the epicenter distance, and K i is a correction term.

[0046] (Magnitude Estimation Procedure 2): The earthquake warning issuing device 100 first calculates a seismic motion index value (for example, maximum P-wave strain velocity value) based on the P-wave by detecting the arrival of S-waves (arrival time of S-waves) in the seismic waves W caused by the earthquake E for each set position (measurement point) of each measurement channel C based on the strain amount indicated by each measurement result RC. The detection of the arrival of S-waves in the earthquake warning issuing device 100 can be done, for example, by replacing the P-waves in the above-mentioned epicenter determination procedure 1 with S-waves and calculating the STA of the S-waves. s and S-wave LTA sThe ratio of STA to LTA (= STA / LTA, more specifically, STA s / LTA s ) is used.

[0047] The method for detecting the arrival of S waves in the earthquake warning issuing device 100 is not limited to the method using the ratio of STA to LTA (=STA / LTA) described above, and any method may be used. The seismic motion index value calculated by the earthquake warning issuing device 100 in the magnitude estimation procedure 2 is not limited to the maximum P-wave strain rate, as long as it is an index value related to the P-wave of the seismic motion.

[0048] (Magnitude Estimation Procedure 3): Next, the earthquake warning issuance device 100 uses a regression equation prepared in advance to estimate (calculate) the magnitude of earthquake E for each set position (measurement point) of each measurement channel C. More specifically, the earthquake warning issuance device 100 estimates (calculates) the magnitude for each measurement point by substituting the epicenter distance calculated in epicenter determination procedure 3 and the seismic motion index value (for example, maximum P-wave strain velocity) calculated in the magnitude estimation procedure into the regression equation (formula (3) above) defined in advance in magnitude estimation procedure 1. In other words, the earthquake warning issuance device 100 estimates (calculates) the magnitude of earthquake E for each observation point in the DAS system.

[0049] For example, the earthquake warning issuing device 100 calculates the seismic motion index value E i and epicenter distance D i The magnitude M for each measurement point is estimated (calculated) by repeating the calculation of estimating the magnitude M by substituting each of the above values ​​while changing the setting position (measurement point) of each measurement channel C.

[0050]

number

[0051] The magnitude estimated (calculated) in the magnitude estimation procedure 3 is an earthquake parameter that indicates the scale of the earthquake E that occurred.

[0052] The earthquake warning issuing device 100 performs statistical processing (for example, processing to find the average value or median value) on the estimated (calculated) magnitude for each measurement point.

[0053] By using this procedure (magnitude estimation procedure), the earthquake warning issuance device 100 reduces errors in the estimated (calculated) magnitude. In other words, the earthquake warning issuance device 100 improves the accuracy of the estimated (calculated) magnitude.

[0054] As a result, the earthquake warning issuing device 100 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.

[0055] The earthquake warning issuing device 100 then controls the actual issuance of an earthquake warning AL based on the estimated (calculated) epicenter distance and magnitude M. 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.

[0056] 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 of 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 T).

[0057] When a vibration waveform VW detected by the seismometer S is output, the earthquake warning issuance device 100 may use the vibration waveform VW to estimate (calculate) earthquake parameters, i.e., based on seismic waves observed at a single observation point. In this case, the earthquake warning issuance device 100 may determine whether or not an earthquake warning AL needs to be issued based on the earthquake parameters estimated (calculated) based on the vibration waveform VW (i.e., earthquake parameters based on a single observation point) in addition to the epicenter distance estimated (calculated) in the epicenter determination procedure 3 or the epicenter determination procedure 4 and the magnitude M estimated (calculated) in the magnitude estimation procedure 3 (in other words, the earthquake parameters estimated (calculated) based on the measurement results RC of multiple measurement points (respective measurement channels C) in the DAS system). The method for estimating earthquake parameters based on the vibration waveform VW in the earthquake warning issuance device 100 may be the same as the method used in existing earthquake early warning systems, or equivalent to the method for estimating (calculating) the epicenter distance and magnitude for a single observation point in the epicenter determination procedure and magnitude estimation procedure described above. Therefore, a detailed description of the method by which the earthquake warning issuing device 100 estimates earthquake specifications based on the vibration waveform VW output by the seismometer S will be omitted.

[0058] [Earthquake warning issuance control in earthquake warning issuing devices] Next, an example of the process in which the earthquake warning issuance device 100 issues an earthquake warning AL based on the measurement results RC output by each measurement channel C of the DAS system will be described. FIG. 3 is a flowchart showing an example of the process flow in which the earthquake warning issuance device 100 issues an earthquake warning AL. The processes in this flowchart are repeatedly executed in the earthquake warning issuance device 100 while the earthquake early warning system is in operation. In the following description, it is assumed that the regression equation shown in equation (3) above is defined in advance. In the following description, for ease of explanation, the setting position (measurement point) of each measurement channel C will be simply referred to as the "measurement point." Furthermore, in the following description, the process of the earthquake warning issuance device 100 when a vibration waveform VW detected by the seismometer S is output will be omitted.

[0059] The earthquake warning issuing device 100 sequentially acquires the measurement results RC output from each measurement channel C of the DAS system (step S100). Then, the earthquake warning issuing device 100 detects the arrival of P waves (the arrival time of P waves) in the seismic waves W caused by the earthquake E that has occurred for each measurement point from which the measurement results RC have been acquired (step S110). The earthquake warning issuing device 100 continues to acquire the measurement results RC in step S100 and detect the arrival of P waves in step S110 during the subsequent processing.

[0060] The earthquake warning issuing device 100 determines whether the number of measurement points at which the arrival of P waves was detected in step S110 exceeds a first predetermined number (step S200). If it is determined in step S200 that the number of measurement points at which the arrival of P waves was detected does not exceed the first predetermined number, the earthquake warning issuing device 100 returns the process to step S100 and repeats obtaining the measurement results RC output by the measurement channel C and detecting the arrival of P waves.

[0061] On the other hand, if it is determined in step S200 that the number of measurement points at which the arrival of P waves has been detected exceeds the first predetermined number, the earthquake warning issuance device 100 determines the epicenter corresponding to each measurement point (step S210).

[0062] Next, the earthquake warning issuing device 100 estimates (calculates) the epicenter distance between each measurement point and the epicenter based on the epicenter corresponding to each of the determined measurement points (step S300). As a result, the earthquake warning issuing device 100 can determine (primary determination) based on the estimated epicenter distance whether the earthquake E that has just occurred is one whose epicenter is at a distance that requires the issuance of an earthquake warning AL to stop the train T.

[0063] Next, the earthquake warning issuing device 100 detects the arrival of S waves (arrival times of S waves) in the seismic waves W caused by the earthquake E for each measurement point where the measurement results RC were acquired (step S400). Then, the earthquake warning issuing device 100 calculates a seismic motion index value (for example, maximum P-wave strain velocity value) based on the detected arrival of S waves (step S410).

[0064] Next, the earthquake warning issuance device 100 estimates (calculates) the magnitude of earthquake E for each measurement point using a regression equation (step S500). More specifically, the earthquake warning issuance device 100 estimates (calculates) the magnitude for each measurement point (each observation point of earthquake E in the DAS system) by substituting the epicenter distance estimated (calculated) in step S300 and the seismic motion index value calculated in step S410 into a predefined regression equation for each measurement point. Then, the earthquake warning issuance device 100 performs statistical processing on the estimated (calculated) magnitude for each measurement point (step S510). As a result, the earthquake warning issuance device 100 can determine (secondary determination) whether the earthquake E that has occurred this time is of a magnitude that requires the issuance of an earthquake warning AL to stop train T, based on the magnitude after statistical processing.

[0065] The earthquake warning issuance device 100 determines whether or not it is necessary to issue an earthquake warning AL based on the determination results of the primary determination and the secondary determination described above (step S600). That is, the earthquake warning issuance device 100 determines whether or not the earthquake E that has just occurred is an earthquake E with earthquake specifications that require the issuance of an earthquake warning AL to stop the train T, based on the epicenter distance estimated (calculated) in step S300 and the magnitude estimated (calculated) in step S500. If it is determined in step S600 that it is not necessary to issue an earthquake warning AL, the earthquake warning issuance device 100 proceeds to the process of step S700.

[0066] On the other hand, if it is determined in step S600 that an earthquake warning AL needs to be issued, the earthquake warning issuing device 100 issues an earthquake warning AL to, for example, a train T traveling on the railroad R (step S610). This allows the driver of the train T for which an earthquake warning AL has been issued to safely stop (halt) the train T.

[0067] The earthquake warning issuing device 100 determines whether the number of measurement points at which the arrival of P waves has been detected (i.e., the total number of measurement points), including the number of new measurement points that are being continuously measured, is equal to or greater than a second predetermined number (step S700). If it is determined in step S700 that the total number of measurement points at which the arrival of P waves has been detected is equal to or greater than the second predetermined number, the earthquake warning issuing device 100 ends the series of processes in this flowchart corresponding to the earthquake E that has just occurred, returns the process to step S100, and starts the process in this flowchart corresponding to the next earthquake.

[0068] On the other hand, if it is determined in step S700 that the total number of measurement points that have detected the arrival of P waves has reached or exceeded the second predetermined number, the earthquake warning issuance device 100 determines whether the number of measurement points that have continued to detect the arrival of P waves has newly increased to or exceeded the increase number (step S710). If it is determined in step S710 that the number of measurement points that have detected the arrival of P waves has newly increased to or exceeded the increase number, the earthquake warning issuance device 100 returns the process to step S210 and repeats the processes of steps S210 to S710. In other words, the earthquake warning issuance device 100 recalculates the epicenter determination corresponding to each new measurement point, estimates (calculates) the epicenter distance and magnitude based on each recalculated epicenter, and repeatedly determines whether or not to issue an earthquake warning AL that includes the epicenter distance and magnitude for the new measurement point.

[0069] On the other hand, if it is determined in step S710 that the number of measurement points that have detected the arrival of P waves is not greater than the increased number and has not newly increased, the earthquake warning issuing device 100 returns the process to step S100 and repeats the processes of steps S100 to S710. In other words, the earthquake warning issuing device 100 continues to acquire measurement results RC from new measurement points and detect the arrival of P waves, and continues the series of processes in this flowchart in response to the earthquake E that has just occurred.

[0070] In the flowchart shown in Figure 3, it has been explained that the respective processes are repeatedly executed in the earthquake warning issuance device 100 while the earthquake early warning system is operating, even if earthquake E has not occurred, but the process of issuing an earthquake warning AL in the earthquake warning issuance device 100 is not limited to the flow of the process in the flowchart shown in Figure 3. For example, the earthquake warning issuance device 100 may repeatedly execute only the acquisition of the measurement result RC in step S100 and the detection of the arrival of P waves in step S110, and start the processes from step S200 onwards when it first detects the arrival of P waves of the seismic waves W caused by the earthquake E that has occurred.

[0071] [Example of the configuration of an earthquake warning device] Next, a description will be given of an example of the configuration of the earthquake warning issuance device 100. Fig. 4 is a diagram showing an example of the configuration of the earthquake warning issuance device 100. The earthquake warning issuance device 100 includes, for example, a storage unit 110 and a processing circuit 120.

[0072] The storage unit 110 stores a regression equation that has been prepared (calculated) in advance. The storage unit 110 may store data and information used by each function in the processing circuit 120 of the earthquake warning issuance device 100 when performing processing. The storage unit 110 is, for example, a storage device such as a semiconductor memory element such as a read-only memory (ROM), a random access memory (RAM), or a flash memory, or a hard disk drive (HDD). While FIG. 1 illustrates a configuration in which the storage unit 110 is provided in the earthquake warning issuance device 100, the storage unit 110 may be an external storage device connected to the earthquake warning issuance device 100. If the storage unit 110 is an external storage device, it may be, for example, a server device or storage device incorporated in a cloud computing system that is connected to the earthquake warning issuance device 100 via a network (not shown). The network (not shown) may include, for example, the Internet, a wide area network (WAN), a local area network (LAN), a provider device, a wireless base station, etc.

[0073] The processing circuit 120 executes processes such as a measurement result acquisition function 121, a P-wave arrival detection function 122, an epicenter determination function 123, an epicenter distance estimation function 124, an S-wave arrival detection function 125, a seismic motion index value calculation function 126, a magnitude estimation function 127, a vibration waveform acquisition function 128, an earthquake parameter estimation function 129, and an earthquake warning issuance function 130. 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.

[0074] 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.

[0075] The measurement result acquisition function 121 sequentially acquires the measurement results RC output by each measurement channel C. The measurement result acquisition function 121 sequentially outputs the acquired measurement results RC to the P wave arrival detection function 122 and the S wave arrival detection function 125, respectively.

[0076] The measurement result acquisition function 121 may be configured to sequentially store the acquired measurement results RC in the storage unit 110, and output the acquired measurement results RC to the P wave arrival detection function 122 and the S wave arrival detection function 125, respectively, by each reading out the measurement results RC stored in the storage unit 110. In this case, the measurement result acquisition function 121 may be configured to always store the measurement results RC for a predetermined period (for example, a period required for processing of epicenter determination and magnitude estimation) from the latest measurement result RC, regardless of the storage capacity allocated to the storage unit 110, by, for example, storing the acquired measurement results RC up to the allocated storage capacity in the storage unit 110 and then overwriting the oldest measurement result RC with the newly acquired measurement result RC.

[0077] The P-wave arrival detection function 122 sequentially detects the arrival of P-waves of the seismic waves W caused by the earthquake E that has occurred at each measurement point (P-wave arrival time) based on the measurement results RC sequentially output by the measurement result acquisition function 121 (see epicenter determination procedure 1). The P-wave arrival detection function 122 sequentially outputs information on the detected P-wave arrival to the epicenter determination function 123.

[0078] P-wave arrival detection function 122 may be configured to store information about the detected P-wave arrival in storage unit 110, notify epicenter determination function 123 that the information about P-wave arrival has been stored, and output the information about the detected P-wave arrival to epicenter determination function 123 by having epicenter determination function 123 read out the information about P-wave arrival stored in storage unit 110. In this case, P-wave arrival detection function 122 may be configured to store the information about the detected P-wave arrival in a predetermined storage area allocated in storage unit 110, and delete the stored information about P-wave arrival after the current earthquake E has subsided, thereby always storing information about P-wave arrival only when earthquake E occurs.

[0079] The P wave arrival detection function 122 is an example of a function that “detects the arrival time of a P wave.” The P wave arrival detection function 122 is an example of a “P wave arrival detection unit.”

[0080] The epicenter determination function 123 sequentially determines the epicenter corresponding to each measurement point based on the information on the P-wave arrival sequentially output by the P-wave arrival detection function 122 (see epicenter determination procedure 2 and epicenter determination procedure 4). The epicenter determination function 123 sequentially outputs information on the determined epicenter to the epicenter distance estimation function 124.

[0081] The epicenter determination function 123 may be configured to store information about the determined epicenter in the storage unit 110, notify the epicenter distance estimation function 124 that the epicenter information has been stored, and output the determined epicenter information to the epicenter distance estimation function 124 by the epicenter distance estimation function 124 reading out the epicenter information stored in the storage unit 110. In this case, the epicenter determination function 123 may be configured to store the determined epicenter information in a predetermined storage area allocated to the storage unit 110, and delete the stored epicenter information after the current earthquake E has subsided, thereby always storing epicenter information only when earthquake E occurs.

[0082] The epicenter determination function 123 is an example of a function for "determining the epicenter of an earthquake." The epicenter determination function 123 is an example of an "epicenter determination unit."

[0083] The epicenter distance estimation function 124 sequentially estimates (calculates) the epicenter distance corresponding to each measurement point based on the epicenter information sequentially output by the epicenter determination function 123 (see epicenter determination procedure 3 and epicenter determination procedure 4). The epicenter distance estimation function 124 sequentially outputs the estimated (calculated) epicenter distance information to the magnitude estimation function 127 and the earthquake warning issuance function 130.

[0084] The epicenter distance estimation function 124 may be configured to store information about the estimated epicenter distance in the storage unit 110, notify each of the magnitude estimation function 127 and the earthquake warning issuance function 130 that the epicenter distance information has been stored, and output the estimated epicenter distance information to the magnitude estimation function 127 and the earthquake warning issuance function 130 by each reading out the epicenter distance information stored in the storage unit 110. In this case, the epicenter distance estimation function 124 may be configured to store the estimated epicenter distance information in a predetermined storage area allocated to the storage unit 110, and delete the stored epicenter distance information after the current earthquake E has subsided, thereby always storing information about the epicenter distance only when earthquake E occurs.

[0085] The epicenter distance estimation function 124 is an example of a function for "estimating an epicenter distance." The epicenter distance estimation function 124 is an example of an "epicenter distance estimation unit."

[0086] The S-wave arrival detection function 125 sequentially detects the arrival of S-waves of seismic waves W caused by the earthquake E at each measurement point (the arrival time of the S-waves) based on the measurement results RC sequentially output by the measurement result acquisition function 121 (see magnitude estimation procedure 2). The S-wave arrival detection function 125 sequentially outputs information on the detected arrival of S-waves to the seismic motion index value calculation function 126.

[0087] The S-wave arrival detection function 125 may be configured to store information about the detected arrival of S waves in the storage unit 110, notify the seismic activity index value calculation function 126 that the information about the arrival of S waves has been stored, and have the seismic activity index value calculation function 126 read out the information about the arrival of S waves stored in the storage unit 110, thereby outputting the information about the detected arrival of S waves to the seismic activity index value calculation function 126. In this case, the S-wave arrival detection function 125 may be configured to store the information about the detected arrival of S waves in a predetermined storage area allocated in the storage unit 110, and delete the stored information about the arrival of S waves after the current earthquake E has subsided, thereby always storing information about the arrival of S waves only when earthquake E has occurred.

[0088] The S wave arrival detection function 125 is an example of a function that "detects the arrival time of S waves."

[0089] The earthquake motion index value calculation function 126 sequentially calculates earthquake motion index values ​​corresponding to each measurement point based on the information on the arrival of S waves sequentially output by the S-wave arrival detection function 125 (see magnitude estimation procedure 2). The earthquake motion index value calculation function 126 sequentially outputs the calculated earthquake motion index values ​​to the magnitude estimation function 127.

[0090] The earthquake motion index value calculation function 126 may be configured to store the calculated earthquake motion index value in the storage unit 110, notify the magnitude estimation function 127 that the earthquake motion index value has been stored, and have the magnitude estimation function 127 read out the earthquake motion index value stored in the storage unit 110, thereby outputting the calculated earthquake motion index value to the magnitude estimation function 127. In this case, the earthquake motion index value calculation function 126 may be configured to store the calculated earthquake motion index value in a predetermined storage area allocated in the storage unit 110, and delete the stored earthquake motion index value after the current earthquake E has subsided, thereby always storing the earthquake motion index value only when earthquake E occurs.

[0091] The earthquake motion index value calculation function 126 is an example of a function that “calculates an earthquake motion index value.” The earthquake motion index value calculation function 126 is an example of a “earthquake motion index value calculation unit.”

[0092] The magnitude estimation function 127 estimates (calculates) the magnitude corresponding to each measurement point using a regression equation stored in the storage unit 110 (see magnitude estimation procedure 3). More specifically, the magnitude estimation function 127 estimates (calculates) the magnitude by substituting the information on the epicenter distance sequentially output by the epicenter distance estimation function 124 and the seismic motion index value sequentially output by the seismic motion index value calculation function 126 into the regression equation stored in the storage unit 110. The magnitude estimation function 127 sequentially outputs the estimated (calculated) magnitude information to the earthquake warning issuance function 130.

[0093] The magnitude estimation function 127 may be configured to store the estimated magnitude information in the memory unit 110, notify the earthquake warning issuance function 130 that the magnitude information has been stored, and output the estimated magnitude information to the earthquake warning issuance function 130 by the earthquake warning issuance function 130 reading out the magnitude information stored in the memory unit 110. In this case, the magnitude estimation function 127 may be configured to store the estimated magnitude information in a predetermined memory area allocated in the memory unit 110, and delete the stored magnitude information after the current earthquake E has subsided, thereby always storing magnitude information only when earthquake E occurs.

[0094] The magnitude estimation function 127 is an example of a function that "estimates the magnitude of an earthquake." The magnitude estimation function 127 is an example of an "earthquake magnitude estimation unit."

[0095] The vibration waveform acquisition function 128 sequentially acquires the vibration waveform VW output by the seismometer S. The vibration waveform acquisition function 128 sequentially outputs the acquired vibration waveform VW to the earthquake parameter estimation function 129.

[0096] The vibration waveform acquisition function 128 may be configured to sequentially store the acquired vibration waveforms VW in the storage unit 110, and the earthquake parameter estimation function 129 may read out the vibration waveforms VW stored in the storage unit 110, thereby outputting the acquired vibration waveforms VW to the earthquake parameter estimation function 129. In this case, the vibration waveform acquisition function 128 may be configured to always store vibration waveforms VW for a predetermined period (for example, a period required to estimate (calculate) earthquake parameters based on the vibration waveforms VW) starting from the latest vibration waveform VW, regardless of the storage capacity allocated to the storage unit 110, by, for example, storing the acquired vibration waveforms VW up to the allocated storage capacity in the storage unit 110 and then overwriting the oldest vibration waveform VW with the newly acquired vibration waveform VW.

[0097] The earthquake parameter estimation function 129 estimates the earthquake parameters of the earthquake E at a single observation point based on the vibration waveform VW sequentially output by the vibration waveform acquisition function 128. Furthermore, the earthquake parameter estimation function 129 performs noise identification processing to identify whether the vibration waveform VW is a vibration caused by the earthquake E, based on the vibration waveform VW sequentially output by the vibration waveform acquisition function 128. If the earthquake parameter estimation function 129 identifies that the vibration waveform VW is a vibration caused by the earthquake E, it outputs information about the earthquake parameters estimated at the single observation point to the earthquake warning issuance function 130.

[0098] The earthquake parameter estimation function 129 may be configured to store information about earthquake parameters estimated at a single observation point in the storage unit 110, notify the earthquake warning issuance function 130 that the earthquake parameter information has been stored, and have the earthquake warning issuance function 130 read out the earthquake parameters stored in the storage unit 110, thereby outputting the information about earthquake parameters estimated at a single observation point to the earthquake warning issuance function 130. In this case, the earthquake parameter estimation function 129 may be configured to store the estimated earthquake parameters in a predetermined storage area allocated to the storage unit 110, and delete the stored earthquake parameters after the earthquake E has subsided, thereby always storing the earthquake parameters estimated at a single observation point only when the earthquake E has occurred.

[0099] The method of estimating earthquake parameters in the earthquake parameter estimation function 129 is similar to the method of estimating earthquake parameters at a single observation point in an existing earthquake early warning system. The earthquake parameter estimation function 129 may have the same configuration as the components that estimate earthquake parameters in an existing earthquake early warning system. In other words, the earthquake parameter estimation function 129 may have any configuration as long as it is configured to estimate the earthquake parameters of the earthquake E that recently occurred based on the vibration waveform VW at a single observation point output by the vibration waveform acquisition function 128. Therefore, a detailed description of the method of estimating earthquake parameters in the earthquake parameter estimation function 129 will be omitted.

[0100] The earthquake warning issuance function 130 determines whether or not it is necessary to issue an earthquake warning AL to stop the train T, based on the information on the epicenter distance sequentially output by the epicenter distance estimation function 124 and the information on the magnitude sequentially output by the magnitude estimation function 127 (in other words, earthquake specifications based on multiple measurement points of the DAS system). At this time, the earthquake warning issuance function 130 performs statistical processing on the magnitude information sequentially output by the magnitude estimation function 127. The statistical processing may be performed when the magnitude estimation function 127 outputs the magnitude information to the earthquake warning issuance function 130.

[0101] When the earthquake parameter estimation function 129 outputs information on earthquake parameters estimated at a single observation point, the earthquake warning issuance function 130 may determine whether or not it is necessary to issue an earthquake warning AL, taking into account the information on earthquake parameters based on the single observation point in addition to the earthquake parameters based on the multiple measurement points of the DAS system described above.

[0102] When it is determined that an earthquake warning AL needs to be issued, the earthquake warning issuance function 130 actually issues the earthquake warning AL, which allows the driver of the train T for which an earthquake warning AL has been issued to safely stop (halt) the train T.

[0103] The earthquake warning issuance function 130 is an example of a function that "controls the issuance of earthquake warnings." The earthquake warning issuance function 130 is an example of an "earthquake warning issuance unit."

[0104] With this configuration and processing, the earthquake warning issuing device 100 uses the DAS system to measure strain associated with seismic motion caused by seismic waves W of the earthquake E that has occurred at multiple measurement points (respective measurement channels C). Then, based on the measurement results RC from each measurement point, the earthquake warning issuing device 100 estimates (calculates) the earthquake specifications (epicenter distance and magnitude) of the earthquake E with high accuracy. In other words, existing earthquake early warning systems estimate (calculate) the earthquake specifications of the earthquake E that has occurred based on seismic waves observed at a single observation point, which results in large errors in the estimated earthquake specifications. In order to reduce the errors in the earthquake specifications, existing earthquake early warning systems require a certain amount of time to pass between when a seismometer S first detects seismic motion caused by seismic waves W of the earthquake E and when another seismometer S detects the seismic motion, making it impossible to estimate (calculate) the earthquake specifications with high accuracy. In contrast, the earthquake warning issuing device 100 can estimate (calculate) earthquake parameters based on the seismic motions measured by multiple measurement channels C that are set at short intervals, such as 5 meters apart (i.e., set at high density). The earthquake warning issuing device 100 can reduce errors in the estimated (calculated) earthquake parameters by performing statistical processing on the estimated (calculated) magnitude. Therefore, the earthquake warning issuing device 100 shortens the time that elapses between the first detection of seismic motion by a measurement channel C and the detection of seismic motion by other measurement channels C, enabling it to estimate (calculate) earthquake parameters more accurately than existing earthquake early warning systems. The earthquake warning issuing device 100 can accurately determine whether the earthquake E that has occurred is one whose epicenter is within a distance that requires the issuance of an earthquake warning AL to stop the train T, and whether the magnitude of the earthquake E requires the issuance of an earthquake warning AL. Based on the determination results, the issuance of an earthquake warning AL according to the earthquake E can be appropriately controlled.In other words, the earthquake warning issuing device 100 can actually issue an earthquake warning AL when the earthquake E that has occurred has an epicenter within a distance that requires the issuance of an earthquake warning AL to stop the train T and is of a magnitude that requires the issuance of an earthquake warning AL. In other words, an earthquake warning AL is issued when the earthquake E that has occurred is likely to cause damage to the train T, and an earthquake warning AL is not issued when the earthquake E is not likely to cause damage to the train T. This makes it possible for the earthquake warning issuing device 100 to reduce unnecessary stops (halts) of the train T that are caused by issuing an unnecessary earthquake warning AL for a train T that is not likely to suffer damage when an earthquake E occurs. In other words, the earthquake warning issuing device 100 can improve the stability of the operation of the train T when an earthquake E occurs. As a result, the earthquake warning issuing device 100 can issue an earthquake warning AL that is immediate and highly reliable, based on seismic waves W obtained by measuring the earthquake E at multiple points (measurement points). Furthermore, in an early earthquake warning system equipped with the earthquake warning issuance device 100, it is possible to improve the reliability and accuracy of the control of the issuance of earthquake warnings AL, and when earthquake E occurs, it is possible to quickly issue earthquake warnings AL.

[0105] As described above, the earthquake warning issuance device 100 of the embodiment detects seismic motion at multiple measurement points (observation points) based on the measurement results RC output in real time by each measurement channel C of the DAS system. Then, the earthquake warning issuance device 100 of the embodiment estimates (calculates) earthquake specifications with high accuracy based on the multiple measurement results RC output in real time, and controls the issuance of an earthquake warning AL to stop the train T. As a result, in an earthquake early warning system equipped with the earthquake warning issuance device 100 of the embodiment, when an earthquake E occurs, the issuance of an earthquake warning AL can be suitably controlled, reducing the number of unnecessary trains T stopped (stopped), and allowing necessary trains T to be safely stopped (stopped). As a result, in an earthquake early warning system equipped with the earthquake warning issuance device 100 of the embodiment, the stability of train operation of the train T can be improved even when an earthquake E occurs.

[0106] In the above-described embodiment, the case where the earthquake warning issuing device 100 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 embodiment, the case where the earthquake warning issuing device 100 directly issues an earthquake warning AL to the train T has been described. However, the earthquake warning issuing device 100 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 100 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 about the earthquake warning AL to be issued. In this case, the control of issuance of an earthquake warning AL by the earthquake warning issuing device 100 may be equivalent to the control of issuance of an earthquake warning AL by the earthquake warning issuing device 100 in the above-described embodiment. Therefore, a detailed description of the control of issuance of an earthquake warning AL by the earthquake warning issuing device 100 in a configuration in which an earthquake warning AL is not directly issued to the train T will be omitted.

[0107] 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]

[0108] 100 Earthquake warning device 110...Storage section 120 Processing circuit 121 Measurement result acquisition function 122 P wave arrival detection function 123 Epicenter Determination Function 124···Epicenter distance estimation function 125···S wave arrival detection function 126 Earthquake motion index value calculation function 127···Magnitude estimation function 128... Vibration waveform acquisition function 129 Earthquake Parameter Estimation Function 130 Earthquake warning function C Measurement channel S...Seismograph

Claims

1. The computer Based on measurement data measured at a plurality of measurement points provided on an optical fiber cable installed along a railway line, the arrival time of P waves from the earthquake that has occurred is detected for each of the measurement points; determining the epicenter of the earthquake based on the arrival time of the P wave for each of the measurement points; For each of the measurement points, estimate a distance between the measurement point and the corresponding epicenter; calculating a seismic motion index value based on the P wave for each measurement point based on the measurement data; Estimating the magnitude of the earthquake for each of the measurement points based on a predefined regression equation, the epicenter distance, and the seismic motion index value; Controlling the issuance of an earthquake warning based on the epicenter distance and the earthquake magnitude. How earthquake warnings are issued.

2. The computer controlling the issuance of the earthquake warning based on the epicenter distance and the earthquake magnitude obtained by performing statistical processing on the earthquake magnitude corresponding to each of the measurement points; The earthquake warning issuing method according to claim 1.

3. The regression equation is calculated based on measurement data obtained by measuring earthquakes that have occurred in the past at a plurality of the measurement points, and is defined in advance. The earthquake warning issuing method according to claim 2.

4. The seismic motion index value is calculated by detecting the arrival time of an S wave due to the earthquake that has occurred for each of the measurement points based on the measurement data. The earthquake warning issuing method according to claim 3.

5. The computer The magnitude of the earthquake is estimated by substituting the epicenter distance and the seismic motion index value into the regression equation. The earthquake warning issuing method according to claim 4.

6. The computer When the number of measurement points at which the arrival time of the P wave is detected exceeds the first detection number, determining the epicenter at the measurement point where the arrival time of the P wave was detected; Estimating the epicenter distance at the measurement point where the arrival time of the P wave was detected; Calculating the seismic motion index value at the measurement point where the arrival time of the P wave was detected; Estimating the magnitude of the earthquake at the measurement point where the arrival time of the P wave was detected. The earthquake warning issuing method according to claim 5.

7. The computer When the number of measurement points at which the arrival time of the P wave is detected is newly increased by a predetermined increase number or more, determining the epicenter at the increased measurement points; Estimating the epicenter distance at the increased measurement points; Calculating the seismic motion index values ​​at the increased measurement points; Estimating the magnitude of the earthquake at the increased measurement points; Controlling the issuance of the earthquake warning based on the epicenter distance of the increased measurement points and the earthquake magnitude. The earthquake warning issuing method according to claim 6.

8. a P-wave arrival detection unit that detects the arrival time of P-waves from an earthquake that has occurred at each of a plurality of measurement points based on measurement data measured at the measurement points on an optical fiber cable installed along the railway line; an epicenter determination unit that determines the epicenter of the earthquake for each of the measurement points based on the arrival time of the P wave; an epicenter distance estimation unit that estimates an epicenter distance between each of the measurement points and the corresponding epicenter; a seismic motion index value calculation unit that calculates a seismic motion index value based on the P wave for each measurement point based on the measurement data; an earthquake magnitude estimation unit that estimates the magnitude of the earthquake for each of the measurement points based on a predefined regression equation, the epicenter distance, and the seismic motion index value; an earthquake warning issuing unit that controls the issuance of an earthquake warning based on the epicenter distance and the earthquake magnitude; An earthquake warning issuing device equipped with:

9. On the computer, Based on measurement data measured at a plurality of measurement points provided on an optical fiber cable installed along a railway line, the arrival time of P waves from an earthquake that has occurred is detected for each of the measurement points; determining the epicenter of the earthquake for each of the measurement points based on the arrival time of the P wave; For each of the measurement points, estimate a distance between the measurement point and the corresponding epicenter; calculating a seismic motion index value based on the P wave for each measurement point based on the measurement data; estimating the magnitude of the earthquake for each of the measurement points based on a predefined regression equation, the epicenter distance, and the seismic motion index value; Controlling the issuance of an earthquake warning based on the epicenter distance and the earthquake magnitude. program.

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