JP5939886B2 - Earthquake motion convergence judgment system - Google Patents

Description

  The present invention relates to a ground motion convergence determination system for discriminating whether an observation target point after an earthquake occurs is based on a post-swing of an S wave of the earthquake or a P wave of a new earthquake. It is.

  In recent years, earthquake early warning systems have been operated that use earthquake early warnings from the Japan Meteorological Agency to predict the intensity of ground motion at target locations and notify the occurrence of earthquakes and the magnitude of shaking before reaching the earthquake. In addition, an earthquake early warning system that predicts the magnitude of the main motion (S wave) that reaches the point from the initial tremor (P wave) of the earthquake using a seismometer installed at the target point has been developed. .

  Furthermore, in the following Patent Document 1, an earthquake disaster prevention system is proposed in which the emergency earthquake bulletin and a seismometer installed at a target point are used in combination to control equipment installed at the point. This earthquake disaster prevention system is a first earthquake disaster prevention system unit that outputs a first control signal that causes an emergency broadcast alarm or a production device to be stopped when a seismic intensity is measured by a seismic intensity meter or more. Receive the earthquake early warning including the location of the epicenter and magnitude information and analyze it to predict the seismic intensity and arrival time of the main earthquake motion. A second earthquake disaster prevention system unit that outputs a second control signal for causing the emergency broadcast alarm, the manufacturing apparatus, etc. to be stopped, and further considering the prediction error of the second earthquake disaster prevention system unit, The second threshold value for outputting the second control signal from the second earthquake disaster prevention system unit is set to a seismic intensity higher than the first threshold value for outputting the first control signal from the first earthquake disaster prevention system unit. By, it is provided with a control means for operating the stop of such manufacturing apparatus control target seismic intensity or more.

By the way, in the actual earthquake observation record, as shown in FIG. 5 , there can be seen an example in which two or more large shakes are continuously observed. In such a case, in the earthquake early warning system that uses the seismometer installed at the target point described above to predict the magnitude of the S wave that reaches the point from the P wave, the waveform observed by the seismometer It is difficult to determine whether the waveform is the subsequent waveform of the S wave due to the first earthquake or the waveform due to the P wave of the subsequent earthquake.

  In addition, when the earthquake early warning is used together, if an earthquake that occurred at another point happens to reach the target point at the same time, it will be recognized as different earthquakes based on the information on the epicenter, Although the strength can be predicted, earthquakes occurring in the same region are regarded as the same earthquake, and the seismic intensity is predicted from information based on the first earthquake.

  In such a case, if the tremor predicted from the P wave of the first earthquake is larger, there is no problem as a warning system, but if the tremor predicted from the P wave of the subsequent earthquake is larger, The seismic intensity results predicted using information obtained from the first earthquake underestimate the actual shaking. For this reason, there is a problem in prediction accuracy. For example, the alarm is not activated for a subsequent earthquake that should originally issue an emergency broadcast alarm, or the device is not stopped for a subsequent earthquake that should stop the equipment. Problem arises.

  Therefore, in order to solve the above problems, it is important to detect and distinguish each successive earthquake from the seismic waveform observed in real time by the seismometer, and for this purpose, the first earthquake has converged It is necessary to judge.

  On the other hand, as a conventional technique for returning an elevator car that is forcibly stopped when an earthquake occurs to normal operation when the earthquake converges, for example, in Patent Document 2 below, the acceleration generated by the earthquake is set according to the intensity of the earthquake. If the seismic sensor detects an earthquake within a certain time after the last detection of the extra low gal, the elevator operates normally. An elevator seismic control operation control device for returning to the above is disclosed.

  However, in the control device, a threshold value such as the extra low gal is set in the seismic detector, and it is determined that the earthquake has converged when the time equal to or less than the threshold value is equal to or greater than a certain value. In the case of an earthquake that does, there is a possibility that it will be regarded as one continuous earthquake depending on the threshold value to be set. Also, if the determination time is lengthened, it becomes impossible to identify two or more earthquakes, and if the time is shortened, it may be determined that the convergence has been made erroneously. Thus, when two or more earthquake motions continue, there is a problem that it is difficult to determine the convergence of the first earthquake with high accuracy.

JP 2009-180508 A Japanese Patent Laid-Open No. 08-245106

  The present invention has been made in view of the above circumstances, and when the earthquake motion due to a plurality of earthquakes continues, it is possible to determine the convergence of each earthquake motion with high accuracy. It is an object of the present invention to provide a seismic motion convergence determination system capable of predicting the magnitude of shaking caused by S waves based on P waves.

In order to solve the above-mentioned problem, the ground motion convergence determination system according to the present invention described in claim 1 is based on a seismometer and the magnitude of the shaking caused by the ground motion continuously observed by the seismometer during an earthquake. And a control means having a calculation means for judging the convergence of the seismic motion due to the seismic motion, wherein the computing means is in the range of 1 to 5 seconds of the absolute value of the acceleration caused by the seismic motion transmitted from the seismometer . Calculates the short time average value within the time and the long time average value within the range of 10 to 20 seconds, and continuously calculates the value obtained by dividing the short time average value by the long time average value. The control means sets in advance a state in which a value obtained by dividing the obtained short-time average value by the long-time average value is equal to or less than a preset threshold value in a range of 0.9 to 1.1. It passed the duration of the range 10 seconds to 20 seconds, which is When, is characterized in that it is determined that the earthquake has converged.

According to the invention described in claim 1 , for each earthquake, the seismic motion is continuously observed by the seismometer, and the fluctuation amount per unit time is calculated by the computing means from the obtained acceleration value of the seismic motion. Since it is determined that the earthquake has converged when the preset amount of time has passed after the state in which the amount of variation is not more than a preset threshold by the control means is calculated continuously, Even when the ground motion due to a plurality of earthquakes continues, the convergence of each ground motion can be determined with high accuracy.

  As a result, if it is incorporated into an earthquake early warning system that predicts the main motion (S wave) from the initial tremor (P wave) of the earthquake by the seismometer installed at the target point, it can detect and identify two or more consecutive earthquake motions. Thus, it is possible to individually predict the main motion due to the subsequent seismic motion without considering the continuous seismic motion as one seismic motion, and to improve the prediction accuracy of the earthquake early warning system.

It is a schematic structure figure showing a 1st embodiment of the present invention. It is a flowchart of the determination process performed in the control means of FIG. It is a graph which shows the result judged by the system of the 1st embodiment of the above. It is a graph which shows the result judged by removing a set value in the system of the first embodiment. It is a graph which shows the waveform of the response acceleration of two continuous earthquakes observed in the past .

(First embodiment)
1 to 4 show a first embodiment of a seismic motion convergence determination system according to the present invention.
As shown in FIG. 1, this convergence determination system uses the seismometer installed in the target building to determine the magnitude of the main motion (S wave) that reaches the point from the initial tremor (P wave) of the earthquake. It is built into the earthquake early warning system that predicts.

  In FIG. 1, reference numeral 1 in the figure denotes a building (structure) such as a semiconductor manufacturing factory in which this early earthquake warning system is installed. (Only one of them is shown.) 2 is installed. In addition, a seismometer 3 for detecting the level of seismic motion at each point is attached to a point A on the site close to the building 1 and a point B in the building 1.

  Here, the seismometer 3 observes the vibration of the building 1 or a nearby site in real time, and the acceleration value by the P wave that is judged to be the start of the earthquake motion is set as the smallest contact output level in advance. When the contact level is exceeded, the observation data is output to the control device (control means) 4.

  This control device 4 is calculated by the calculation means for calculating and predicting the magnitude of the final shaking of the building 1 due to the incoming S wave from the acceleration value due to the P wave from the seismometer 3, and calculated by this calculation means. According to the predicted value, an alarm signal is output via the communication line 5 as necessary, and a schematic configuration is configured from a data transmission unit that outputs a signal for stopping or decelerating the operation of the equipment device 2 via the communication line 6 It has been done.

And the control means of the said convergence determination system is integrated in this control apparatus 4. FIG.
This determination system applies the STA / LTA method (STA: Short-Time Average, LTA: Long-Time Average) used to trigger strong motion observations to determine the convergence of earthquake motion.

In other words, the STA / LTA method tries to capture a rapid change in ground motion by taking the ratio of the short-term average value to the long-term average value (STA / LTA) in the absolute value of the ground motion, In order to detect the sudden rise of the above-mentioned ground motion, a normal short-time of 0.5 to 1 second and a long-time of about 5 to 10 seconds are set, and the STA / LTA sets a predetermined threshold. It is determined that the earthquake motion has arrived when the number of times is exceeded continuously.
Incidentally, STA / LTA (0.1 / 5) in FIGS. 3 and 4 is an example in which a time of 0.1 seconds is set as the Short-Time and a time of 5 seconds is set as the Long-Time.

On the other hand, the present inventors have obtained the knowledge that, in the STA / LTA method, by setting a short time to a certain extent, it can be used for determining the convergence of seismic motion. In other words, the ground is constantly shaking with a very small amplitude called microtremor. This constant fine movement is considered to be close to a steady random process, and STA / LTA is almost 1 in the case of a steady random process. Using this property, as shown in FIG. 3 , it is determined that the ground motion has converged when STA / LTA continuously falls within a certain threshold value for a predetermined time.

Therefore, in the present embodiment, the calculation means calculates the ratio (STA / LTA) of the short time average value to the long time average value from the absolute value of the acceleration of the earthquake motion transmitted from the seismometer 3. It is supposed to be. At this time, when used for convergence determination, the STA / LTA is stabilized to some extent when the STA time is longer than when used as a trigger. It is preferable to set a time in the range of 10 to 20 seconds as Time. Note that STA / LTA (5/10) in FIGS. 3 and 4 indicates a case where a time of 5 seconds is set as the Short-Time and a time of 10 seconds is set as the Long-Time.

  On the other hand, the control device 4 is preset with a predetermined value in the range of 0.9 to 1.1 as the STA / LTA threshold and a predetermined time in the range of 10 to 20 seconds as the duration. . Then, the STA / LTA calculated by the calculation means fluctuates and becomes less than the set value in the range of 0.9 to 1.1, and the state continues for the set time in the range of 10 seconds to 20 seconds. In this case, it is judged that the above-mentioned ground motion has converged.

By the way, as shown in FIG. 4 , when the above STA / LTA threshold is set to a value larger than 1.1 (for example, 1.2) and the above determination is made, it is determined that the ground motion has converged even though it has not converged sufficiently. Ri to cause danger, less than 0.9 (e.g., 0.8) when performing the above determination is set to, danger Rukoto the ground motion will be determined not converged despite the well converged Therefore, it is preferable that the STA / LTA threshold is set to a predetermined value in the range of 0.9 to 1.1, and the duration is set to a predetermined time in the range of 10 to 20 seconds.

Formula 1

1 Building 3 Seismometer 4 Control device (control means)

Claims (1)

A seismometer, and a control means comprising a computing means for judging the convergence of the seismic motion due to the earthquake from the magnitude of the shaking caused by the seismic motion continuously observed by the seismometer during an earthquake,
The calculation means includes a short-time average value of the absolute value of acceleration caused by the earthquake motion transmitted from the seismometer within a time range of 1 second to 5 seconds and a long time value within a time range of 10 seconds to 20 seconds. The average value is calculated, and a value obtained by dividing the short-time average value by the long-time average value is continuously calculated, and the control means calculates the obtained short-time average value as the long-time average value. The earthquake converges when the divided value falls below the preset threshold value in the range of 0.9 to 1.1 after a preset duration of 10 to 20 seconds. A system for determining the convergence of seismic motion, characterized in that it has been determined.

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