Early Earthquake Warning Output Method

Abstract

To provide an earthquake-alarm early output method capable of outputting an appropriate earthquake alarm at an early stage.SOLUTION: An earthquake-alarm early output method includes: assuming that an earthquake of a prescribed scale occurs with a certain location as a seismic center or epicenter, calculating magnitudes of earthquake motion index values at a plurality of observation points around the location and defining them as thresholds corresponding to the plurality of observation points; when an earthquake of the prescribed scale occurs at the location, setting alarm output areas for outputting an earthquake alarm; creating a plurality of data tables recording the thresholds and alarm output areas corresponding to the plurality of observation points, corresponding to a plurality of locations; when an earthquake occurs, if an earthquake motion index value observed at least at one observation point exceeds the threshold corresponding to the one observation point recorded in a first data table out of the plurality of data tables, outputting an earthquake alarm to the alarm output areas recorded in the first data table.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an earthquake early warning output method. [Background technology]

[0002] In a conventional technique known as the threshold exceedance determination method (or specified value exceedance determination method), when seismic motion exceeding a predetermined threshold is observed at a certain earthquake observation point, an alarm is output to stop trains traveling in the corresponding predetermined section (see non-patent documents 1 and 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] S. Yamamoto, M. Tomori, “Earthquake early warning system for railways and its performance”, Journal of Japan Society of Civil Engineers, Vol. 1, pp.322-328, 2013. [Non-patent document 2] 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, 2015 [Non-patent document 3] Masahiro Korenaga, Naoyasu Iwata, Shunroku Yamamoto, Shunta Noda, Satsuki Shimono, Tomoya Ono, "Proposal of a distance attenuation formula taking into account the use of early earthquake information", 66th Annual Academic Conference of the Japan Society of Civil Engineers (2011), I-481, pp.961-962 Summary of the Invention [Problem to be solved by the invention]

[0004] When a very large earthquake occurs, it is necessary to issue a warning to a wide area. In this case, conventional technology known as the threshold exceedance determination method (or specified value exceedance determination method) can quickly issue a warning to areas close to the epicenter based on data from seismic observation points close to the epicenter, but it cannot issue a warning to areas far from the epicenter unless seismic motion exceeding the threshold is observed at a seismometer corresponding to that area (i.e., a seismometer far from the epicenter). In other words, in the case of a very large earthquake, even if large shaking is observed early at an observation point close to the epicenter and it is determined to be a large earthquake, it is necessary to wait for the large shaking to reach a seismometer far from the epicenter before issuing a warning to areas far from the epicenter. This can lead to delays in the warning.

[0005] The problem to be solved by the present invention is to provide an earthquake early warning output method that can output an appropriate earthquake warning early. [Means for solving the problem]

[0006] In the earthquake early warning output method of the present invention, assuming that an earthquake of a predetermined magnitude has occurred with a certain point as its epicenter or epicenter, the magnitudes of the seismic intensity index values ​​at multiple observation points around the point are calculated to set thresholds corresponding to the multiple observation points. An alarm output area for issuing an earthquake alarm is set when an earthquake of a predetermined magnitude occurs at the point. Multiple data tables are created corresponding to the multiple points, in which thresholds corresponding to the multiple observation points and alarm output areas are recorded. When an earthquake occurs, if the seismic intensity index value observed at at least one observation point is equal to or greater than the threshold corresponding to the one observation point recorded in a first data table among the multiple data tables, an earthquake alarm is issued to the alarm output area recorded in the first data table.

[0007] When an earthquake occurs, the seismic activity index values ​​observed at each observation point are compared with the threshold values ​​corresponding to each observation point recorded in multiple data tables. If the seismic activity index value observed at at least one observation point is equal to or greater than the threshold value corresponding to said one observation point recorded in the first data table, it is determined that an earthquake of a predetermined magnitude or greater has occurred near the point corresponding to the first data table. Since the occurrence of an earthquake of a predetermined magnitude and the location of the epicenter or epicenter are determined by comparing the observed seismic activity index values ​​with the threshold value, the computational load is smaller than when calculating the distribution of seismic activity magnitude when an earthquake occurs. When it is determined that an earthquake of a predetermined magnitude has occurred that requires a warning to be issued to a wide area, an earthquake warning is issued to the warning output area recorded in the first data table. When a seismic activity index value is observed at an observation point near the epicenter or epicenter, an earthquake warning is issued to the warning output area before a seismic activity index value is observed at an observation point far from the epicenter or epicenter (closer to the warning output area). This allows for appropriate earthquake warnings to be issued early.

[0008] When an earthquake occurs, if the seismic activity index values ​​observed at m (m is plural) observation points are equal to or greater than the thresholds corresponding to the m observation points recorded in the first data table, an earthquake warning is issued to the warning output area recorded in the first data table. This increases the reliability of the determination that an earthquake of a predetermined magnitude or greater has occurred near a location corresponding to the first data table, thereby enabling appropriate earthquake warnings to be output.

[0009] The magnitude of the seismic motion index values ​​at multiple observation points is calculated using the seismic motion attenuation formula. The magnitude of the seismic motion index value can be calculated with high accuracy.

[0010] If a first magnitude earthquake occurs at a first location among multiple locations, an earthquake warning is set to be output to the first warning output area. If a second magnitude earthquake occurs at a second location among multiple locations, an earthquake warning is set to be output to the first warning output area. If the distance from the first warning output area to the second location is longer than the distance to the first location, the second magnitude is set to be greater than the first magnitude.

[0011] The magnitude of the seismic motion that would occur in the first warning output area if a first-magnitude earthquake occurs at the second location is smaller than the magnitude of the seismic motion that would occur in the first warning output area if a first-magnitude earthquake occurs at the first location. If a first-magnitude earthquake occurs at the second location, it may not be necessary to issue an earthquake warning to the first warning output area. By setting the second magnitude larger than the first magnitude, an appropriate earthquake warning can be issued to the first warning output area. [Effects of the Invention]

[0012] The earthquake early warning output method of the present invention determines the magnitude of an earthquake and the location of its epicenter or epicenter by comparing the observed seismic intensity index value with a threshold value, which reduces the computational load compared to calculating the distribution of seismic intensity at the time of an earthquake. When a seismic intensity index value is observed at an observation point close to the epicenter or epicenter, an earthquake warning is output to the warning output area before a seismic intensity index value is observed at an observation point far from the epicenter or epicenter (closer to the warning output area). This allows for an appropriate earthquake warning to be output early. [Brief explanation of the drawings]

[0013] [Figure 1] An explanatory diagram of the epicenter, warning output area, and observation points. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of an earthquake early warning output method will be described with reference to the drawings. In the earthquake early warning output method according to the embodiment, a data table is created in advance, which includes information on the warning output area and information on the threshold values ​​of the seismic motion index values ​​at a plurality of observation points.

[0015] Figure 1 is an explanatory diagram of the epicenter, warning output areas, and observation points. The vertical axis of Figure 1 is latitude, and the horizontal axis is longitude. The first warning output area A1 is an area where an earthquake warning is issued if an earthquake of a predetermined magnitude occurs with the first point C1 as its epicenter or epicenter. The earthquake warning may include, in addition to the fact that an earthquake has occurred, instructions to suspend railroad vehicle operations. The area may be an administrative unit such as a prefecture or a municipality, or a railway line section. The magnitude of the earthquake is evaluated, for example, using the Japan Meteorological Agency magnitude M, but may also be evaluated using other magnitude index values ​​such as moment magnitude. An earthquake of a predetermined magnitude is a large earthquake, for example, an earthquake of M=7.5. The first point C1, which serves as the epicenter or epicenter, is located on land or sea. The first point C1 is selected based on the set first warning output area A1, the content of the earthquake warning, and the magnitude of the earthquake (predetermined scale). The first point C1 may be set at a location where a seismic motion of a predetermined magnitude will occur in the first warning output area A1 if an earthquake of a predetermined scale occurs at that location. The seismic motion index value may be a maximum acceleration, an instrumental seismic intensity, a SI value (spectral intensity), or the like.

[0016] Observation point P is a location where an observation instrument for seismic index values ​​is installed. Observation points P exist on land and on the seabed. For example, multiple observation points P are distributed approximately every 0.2 degrees in latitude and longitude (approximately every 20 km). Multiple observation points P are not necessarily distributed evenly.

[0017] The threshold value for the seismic motion index value at multiple observation points is calculated as follows: Assume that an earthquake of a certain magnitude has occurred with a certain point as its epicenter or epicenter. The magnitude of the seismic motion index value at multiple observation points located around that point is calculated. The calculation result is used as the threshold value for the seismic motion index value corresponding to the multiple observation points. For example, assume that an earthquake of M=7.5 has occurred with a first point C1 as its epicenter or epicenter. There are multiple observation points P1-P5 located around the first point C1. For example, the maximum acceleration is selected as the seismic motion index value. The magnitude of the maximum acceleration at the multiple observation points P1-P5 is calculated using the seismic motion attenuation formula. An example of the attenuation formula described in Non-Patent Document 3 is shown in Mathematical Formula 1.

[0018]

number

[0019] [Table 1]

[0020] The calculation results of the maximum accelerations at the plurality of observation points P1 to P5 are set as maximum acceleration thresholds S1 to S5 corresponding to the plurality of observation points P1 to P5. The number of observation points for which thresholds are set is not limited to five. The thresholds S1-S5 corresponding to the multiple observation points P1-P5 set as described above and the first warning output area A1 are recorded in a first data table T1 corresponding to the first location C1. The thresholds S1-S5 recorded in the first data table T1 are denoted as thresholds S1(T1)-S5(T1).

[0021] Multiple data tables are created corresponding to multiple locations. For example, multiple locations are set approximately every 0.1 degree in latitude and longitude (approximately every 10 km), and multiple data tables are created. A second data table T2 is created for a second location C2 near the first location C1. Assume that an earthquake with a magnitude of 7.5 occurs with the second location C2 as its epicenter or epicenter. A second warning output area A2 (not shown) is set. Part or all of the second warning output area A2 may overlap with the first warning output area A1. Multiple observation points P5-P9 are located around the second location C2. The magnitude of the maximum acceleration at the multiple observation points P5-P9 is calculated using the seismic motion attenuation formula. The calculated maximum acceleration is set as the maximum acceleration threshold S5-S9 corresponding to the multiple observation points P5-P9. The threshold S5-S9 and the second warning output area A2 are recorded in the second data table T2.

[0022] In an embodiment of the earthquake early warning output method, when an earthquake occurs, the seismic activity index values ​​observed at multiple observation points are compared with thresholds corresponding to the multiple observation points recorded in multiple data tables. The seismic activity index value observed at at least one observation point may be equal to or greater than the threshold corresponding to the one observation point recorded in a first data table among the multiple data tables. When this occurs, it is determined that an earthquake of a predetermined magnitude has occurred near a location corresponding to the first data table. An earthquake warning is then output to the warning output area recorded in the first data table.

[0023] For example, the maximum acceleration observed at observation points P1-P5 is compared with the threshold values ​​S1(T1)-S5(T1) recorded in the first data table T1. The maximum acceleration observed at observation points P1-P5 may be less than the corresponding threshold value S1(T1)-S5(T1). In this case, it is determined that no earthquake of magnitude 7.5 or greater has occurred near the first point C1. In this case, no earthquake warning is issued for the first warning output area A1.

[0024] Similarly, the maximum accelerations observed at observation points P5-P9 are compared with the thresholds S5(T2)-S9(T2) recorded in the second data table T2. There are cases where the maximum accelerations observed at observation points P5-P9 are less than the corresponding thresholds S5(T2)-S9(T2). In this case, it is determined that no earthquake of magnitude 7.5 or greater has occurred near the second point C2. In this case, no earthquake warning is issued for the second warning output area A2.

[0025] On the other hand, there may be cases where the maximum acceleration α5 observed at at least one observation point P5 is equal to or greater than the threshold value S5(T1) recorded in the first data table T1. When this happens, it is determined that an earthquake of magnitude 7.5 or greater has occurred near the first point C1. In this case, an earthquake warning is issued to the first warning output area A1.

[0026] Even in this case, the maximum acceleration α5 observed at observation point P5 may be less than the threshold value S5(T2) recorded in the second data table T2. If the accelerations observed at other observation points P6-P9 are also less than the corresponding threshold values ​​S6(T2)-S9(T2), it is determined that no earthquake of magnitude 7.5 or greater has occurred near the second point C2. In this case, no earthquake warning is issued for the second warning output area A2. As a result, an earthquake warning is issued only for the first warning output area A1.

[0027] Furthermore, the maximum acceleration α5 observed at at least one observation point P5 may exceed both the threshold S5(T1) recorded in the first data table T1 and the threshold S5(T2) recorded in the second data table T2. If the magnitude of the earthquake that occurred significantly exceeds M=7.5, the maximum acceleration α5 may exceed both the threshold S5(T1) and the threshold S5(T2). In this case, it is determined that an earthquake of M=7.5 or greater occurred near the first point C1 and the second point C2. In this case, an earthquake warning is issued for the first warning output area A1 and the second warning output area A2. If part or all of the second warning output area A2 overlaps with the first warning output area A1, it is sufficient to issue only one earthquake warning to the overlapping area.

[0028] When an earthquake of a predetermined magnitude or greater occurs at the same location as a location corresponding to a specific data table, the seismic intensity index values ​​observed at multiple observation points around that location will be equal to or greater than the threshold value corresponding to the multiple observation points recorded in that data table. When an earthquake of a predetermined magnitude or greater occurs at a location a short distance from that location, the seismic intensity index values ​​observed at at least one of the multiple observation points around that location will be equal to or greater than the threshold value corresponding to that one observation point recorded in that data table. It is desirable to prepare multiple data tables so that threshold values ​​corresponding to all observation points are recorded in at least one of the multiple data tables. This makes it possible to identify the occurrence of all earthquakes of a predetermined magnitude or greater and to determine the approximate location of the epicenter or hypocenter.

[0029] When an earthquake occurs, the seismic index values ​​observed at m (m is plural) observation points may exceed the thresholds corresponding to the m observation points recorded in the first table. In this case, it may be determined that an earthquake of a predetermined magnitude or greater has occurred near the point corresponding to the first data table. For example, when m=2, if the maximum accelerations α4 and α5 observed at two observation points P4 and P5 are equal to or greater than the thresholds S4(T1) and S5(T1) recorded in the first data table T1, it is determined that an earthquake of M=7.5 or greater has occurred near the first point C1. This increases the reliability of the above determination and earthquake warning.

[0030] When an earthquake of a first magnitude occurs at a first location among the plurality of locations, an earthquake warning is set to be output to a first warning output area. When an earthquake of a second magnitude occurs at a second location among the plurality of locations, an earthquake warning may also be set to be output to the first warning output area. When the distance from the first warning output area to the second location is longer than the distance to the first location, the second magnitude may be set to be greater than the first magnitude.

[0031] For example, if a first magnitude earthquake occurs at the first point C1, an earthquake warning is set to be output to the first warning output area A1. If a second magnitude earthquake occurs at the second point C2, an earthquake warning is also set to be output to the first warning output area A1. If the distance from the first warning output area A1 to the second point C2 is longer than the distance to the first point C1, the second magnitude is set to be larger than the first magnitude (M=7.5), for example, M=8.0.

[0032] The distance from the first warning output area A1 to the second point C2 is longer than the distance to the first point C1. If an M=7.5 earthquake occurs at the second point C2, the magnitude of the seismic motion that occurs in the first warning output area A1 is smaller than the magnitude of the seismic motion that occurs in the first warning output area A1 if an M=7.5 earthquake occurs at the first point C1. If an M=7.5 earthquake occurs at the second point C2, it may not be necessary to issue an earthquake warning to the first warning output area A1. An earthquake warning needs to be issued to the first warning output area A1 if the second magnitude is larger than the first magnitude (M=7.5). By setting the second magnitude larger than the first magnitude, for example M=8.0, an appropriate earthquake warning can be issued to the first warning output area A1.

[0033] As described above in detail, in the earthquake early warning output method of the embodiment, it is assumed that an earthquake of a predetermined magnitude has occurred with a certain point as its epicenter or epicenter, and the magnitudes of the seismic intensity index values ​​at multiple observation points located around the point are calculated to set thresholds corresponding to the multiple observation points. An alarm output area for issuing an earthquake alarm is set when an earthquake of a predetermined magnitude occurs at the point. Multiple data tables are created corresponding to the multiple points, in which thresholds corresponding to the multiple observation points and alarm output areas are recorded. When an earthquake occurs, if the seismic intensity index value observed at at least one observation point is equal to or greater than the threshold corresponding to the one observation point recorded in a first data table among the multiple data tables, an earthquake alarm is output to the alarm output area recorded in the first data table.

[0034] When an earthquake occurs, the system compares the seismic activity index values ​​observed at multiple observation points with thresholds recorded in multiple data tables corresponding to the multiple observation points. If the seismic activity index value observed at at least one observation point is equal to or greater than the threshold corresponding to the one observation point recorded in a first data table, it is determined that an earthquake of a predetermined magnitude has occurred near the location corresponding to the first data table. Since the occurrence of an earthquake of a predetermined magnitude and the location of the epicenter or epicenter are determined by comparing the observed seismic activity index value with a threshold, the computational load is smaller than when calculating the distribution of seismic activity at the time of an earthquake. When it is determined that an earthquake of a predetermined magnitude has occurred that requires a warning to be issued over a wide area, an earthquake warning is issued to the warning output area recorded in the first data table. When a seismic activity index value is observed at an observation point near the epicenter or epicenter, an earthquake warning is issued to the warning output area before a seismic activity index value is observed at an observation point far from the epicenter or epicenter (closer to the warning output area). This allows for appropriate earthquake warnings to be issued early. This system is easy to put into practical use.

[0035] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and configuration changes, combinations, deletions, etc. are also included within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0036] A1...first warning output area, C1...first location, C2...second location, P1-P9...observation points.

Claims

1. Assuming that an earthquake of a predetermined magnitude has occurred with a certain point as its epicenter or epicenter, calculate the magnitude of the seismic motion index values ​​at a plurality of observation points around the point, and set the magnitudes as thresholds corresponding to the plurality of observation points; setting a warning output area for outputting an earthquake warning when an earthquake of the predetermined magnitude occurs at the location; creating a plurality of data tables in which the thresholds corresponding to the plurality of observation points and the warning output areas are recorded, the data tables corresponding to the plurality of points; When an earthquake occurs, if a seismic activity index value observed at at least one observation point is equal to or greater than the threshold value corresponding to the one observation point recorded in a first data table among the plurality of data tables, an earthquake warning is issued to the warning output area recorded in the first data table. Early earthquake warning output method.

2. When an earthquake occurs, if the seismic intensity index values ​​observed at m (m is plural) observation points become equal to or greater than the threshold values ​​corresponding to the m observation points recorded in the first data table, an earthquake warning is issued to the warning output area recorded in the first data table. The earthquake early warning output method according to claim 1.

3. Calculating the magnitude of the seismic motion index values ​​at the plurality of observation points using a seismic motion attenuation formula.

3. The earthquake early warning output method according to claim 1 or 2.

4. When an earthquake of a first magnitude occurs at a first point among the plurality of points, an earthquake warning is output to a first warning output area; When an earthquake of a second magnitude occurs at a second location among the plurality of locations, an earthquake warning is output to the first warning output area, When a distance from the first warning output area to the second location is longer than a distance from the first location to the second location, the second scale is set to be larger than the first scale.

3. The earthquake early warning output method according to claim 1 or 2.

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