JP4465509B2 - Epicenter distance estimation apparatus, epicenter distance estimation system, and epicenter distance estimation method - Google Patents

Description

  The present invention relates to an epicenter distance estimation apparatus, epicenter distance estimation system, and epicenter distance estimation method for estimating epicenter distance (distance from an observation point to an epicenter) from P wave initial motion data obtained at a single observation point.

Conventionally, an epicenter distance estimation method for estimating the epicenter distance from parameters obtained by focusing on the characteristics of the waveform shape of the seismic wave initial motion part obtained from a seismometer, quantifying the waveform shape by function fitting, The digital waveform data (time series data) of the initial seismic wave obtained from the seismometer is stored in the memory, the offset of the time series data is removed, and the absolute value of the time series data is V (t) [here T is time (seconds)], the time when the earthquake was detected is the time origin (t = 0), and the function y = Bt · e- ^At is applied to the data for a few seconds from the time origin, V (t) = Bt exp (-At) (where B is a parameter related to the temporal change of the initial motion amplitude of the seismic waveform, A is a parameter related to the maximum amplitude of the initial motion portion), and logarithm of both sides of the above equation is taken as log [ (T) / t] = logB−A · log · t, thereby linearizing the parameters A and B, calculating the parameters A and B using a normal least squares method, and the parameter B There was an epicenter distance estimation method characterized in that the epicenter distance was obtained from (Patent Document 1).
Japanese Patent No. 3695579 Takashi Yokota, Research on automatic inspection method, Technical Report of Meteorological Research Institute, No16, P56-P100, 1985

  In the prior art described in Patent Document 1, the epicenter distance is estimated only from the coefficient B. However, since the coefficient B reaches the observation point under the influence of attenuation and scattering in the process of seismic motion propagating through the ground, the source distance (observation point) considering not only the epicenter distance but also the epicenter depth. Is more correlated). As shown in FIG. 9, the epicenter distance and the epicenter distance are the same, but the epicenter distance may be different if the incident angle Θinc is ignored. Therefore, when the epicenter distance is estimated from earthquake data that is deep to some extent, the epicenter distance may be estimated to be large, and the observation points closer to the epicenter are more likely. From the viewpoint of early earthquake detection, the estimation error becomes larger as the observation point is closer to the epicenter where the earthquake specifications can be estimated earliest.

  An object of the present invention is to provide an epicenter distance estimation device, an epicenter distance estimation system, and an epicenter distance estimation method that improve the estimation accuracy of epicenter distances at observation points close to an important epicenter in such early earthquake specification estimation. And

In order to solve the above problems, the epicenter distance estimation apparatus of the present invention includes a detecting means for detecting a seismic wave, a storing means for storing time series data of an initial motion part of the seismic wave, and an absolute value of the time series data of the storing means. Take the value, calculate the envelope, the time when the earthquake was detected as the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope, the coefficient B is obtained, the incident angle θ _inc is obtained from the time series data of the initial motion part of the seismic wave, and the coefficient B and the incident angle θ _inc are expressed by the equation logΔ = C ₁ · log B + C ₂ · f ( θ _inc ) + C ₃ (2)
However, the present invention is characterized by comprising a processing unit that applies to C ₁ , C _2, and C ₃ : a statistically determined constant, f (θ _inc ): a function of incident angle θ _inc , and calculates an epicenter distance. .

The epicenter distance estimation system of the present invention includes a center communication unit that transmits and receives seismic wave information, a storage unit that stores time series data of an initial motion portion of the seismic wave, and an absolute value of the time series data of the storage unit. , The envelope is calculated, the time when the earthquake is detected is the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope, the coefficient B is obtained, the incident angle θ _inc is obtained from the time series data of the initial motion part of the seismic wave, and the coefficient B and the incident angle θ _inc are expressed by the equation logΔ = C ₁ · log B + C ₂ · f ( θ _inc ) + C ₃ (2)
Where C ₁ , C _2, and C _{3 are} statistically determined constants, and f (θ _inc ) is a function of incident angle θ _inc , and a data center having a center processing unit that determines an epicenter distance; A seismometer that transmits and receives earthquake information to and from the data center, and the data center transmits the epicenter distance to the seismometer by the center communication unit.

Furthermore, the epicenter distance estimation method of the present invention takes the absolute value of the time series data of the initial motion part of the seismic wave, calculates the envelope, and sets the time when the earthquake is detected as the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope, the coefficient B is obtained, the incident angle θ _inc is obtained from the time series data of the initial motion part of the seismic wave, and the coefficient B and the incident angle θ _inc are expressed by the equation logΔ = C ₁ · log B + C ₂ · f ( θ _inc ) + C ₃ (2)
However, C ₁ , C ₂ and C _{3 are} statistically determined constants, and f (θ _inc ) is a function of incident angle θ _inc to determine the epicenter distance.

  By using the epicenter distance estimation device, epicenter distance estimation system, and epicenter distance estimation method, the epicenter distance was estimated by correcting the incident angle. It is possible to improve the accuracy of epicenter distance estimation at observation points close to.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a main configuration of the seismometer according to the first embodiment of the present invention. In the figure, 1 is a seismometer, 2 is a communication unit, 3 is a measurement unit, 31 is a sensor, 32 is an A / D converter, 4 is a processing unit, 41 is a processing device, 42 is a ring buffer as storage means, 43 Is a data recording device as storage means, 5 is a clock unit, 6 is a power supply unit, and 7 is a GPS antenna.

  The seismometer 1 includes a communication unit 2, a measurement unit 3, a processing unit 4, a clock unit 5, a power supply unit 6, and the like. The communication unit 2 receives an emergency earthquake bulletin from the Japan Meteorological Agency or information obtained by processing the earthquake (hereinafter referred to as an emergency earthquake bulletin) and outputs it to the processing unit 4 and transmits the earthquake data to the outside. The measurement unit 3 includes a sensor 31, an A / D converter 32, and the like, and outputs a signal obtained by processing the acceleration measured by the sensor 31 by the A / D converter 32 to the processing unit 4. The processing unit 4 includes a processing device 41, a ring buffer 42, a data recording device 43, and the like, and records earthquake data by processing input signals from the communication unit 2 and the measurement unit 3. The processing device 41 estimates the epicenter distance, which is the distance from the observation point to the epicenter, from the information input from the communication unit 2 or the measurement unit 3, and the ring buffer 42 continuously stores temporary storage only for a certain period of time. The data recording device 43 is a device for recording the vibration data estimated as an earthquake out of the data on the ring buffer 42. The clock unit 5 acquires accurate time from the GPS antenna 7 or the like, and the power source unit 6 acquires the power source of the seismometer 1.

  In the embodiment shown in FIG. 1, the seismometer in which the communication unit 2, the measurement unit 3, the processing unit 4, and the like are integrated is shown, but as a modification of the embodiment shown in FIG. 1, as shown in FIG. 2. The communication unit 2 or the measurement unit 3 may be made independent and may be used as the communication device 20 or the measurement device 30.

  The operation of the seismometer 1 having such a configuration will be described. FIG. 3 is a diagram illustrating a flow of the epicenter distance estimation method of the seismometer 1. First, in ST1, the seismometer 1 acquires a digital waveform of the vibration (ST1). Next, in ST2, the offset is removed from the data acquired in step 1 (ST2).

  Subsequently, in ST3-1, a digital filter process for creating an envelope is executed (ST3-1). In the present embodiment, an FIR filter that passes 10-20 Hz, which is a band pass (or high pass) filter that passes a high frequency band, is applied.

  Next, in ST4-1, the absolute value of the data is taken and the envelope is calculated (ST4-1). Subsequently, in ST5-1, the time when the earthquake is detected is set as the time origin (t = 0), and the equation (1) is fitted to the envelope to obtain the coefficients A and B (ST5-1).

y (t) = Bt · exp (−At) (1)
For these steps 1 to 5, reference is made to what is described in Patent Document 1.

  In parallel with steps 3-1 to 5 for obtaining the coefficients, steps 3-2 to 4-2 for estimating the incident angle θ are executed.

  In step 3-2, an incident angle calculation digital filter process is executed (ST3-2). In this embodiment, an FIR filter that passes 1-2 Hz, which is a bandpass (or lowpass) filter that passes a low frequency band, is applied.

Next, in ST4-2, the incidence angle θ _inc is estimated (ST4-2). In this embodiment, as a method for estimating the incident angle θ _{inc of the} earthquake motion from the P wave initial motion data, as shown in FIG. 4, an ellipsoid is applied to the particle trajectory of the earthquake motion of about 1 second from the P wave detection, and the maximum principal axis The method of Non-Patent Document 1 for obtaining the incident angle together with the direction of the epicenter as seen from the observation point by the principal component analysis for obtaining the direction is referred to.

Subsequently, in step 6, the epicenter distance is obtained from the coefficient B obtained in step 5 and the incident angle θ _inc obtained in step 4-2 (ST6). In the present embodiment, Expression (2) is applied as the epicenter distance estimation expression.

log Δ = C ₁ · log B + C ₂ · f (θ _inc ) + C ₃ (2)
However, C ₁ , C ₂ and C ₃ are statistically determined constants. F (θ _inc ) is a function of the incident angle θ _inc .

  Next, the accuracy of the epicenter distance estimated by equation (2) of this embodiment and the epicenter distance estimated by equation (3), which is the method of the conventional Patent Document 1, will be compared.

log Δ = A ₁ · log B + A ₂ (3)
Data to be compared is shown in FIG. 5 and is based on an actual earthquake obtained in the ground of the observation point MYGH03 of the base strong motion observation network of the National Research Institute for Earth Science and Disaster Prevention. As shown in Fig. 5, when the horizontal axis is the epicenter distance and the vertical axis is the epicenter distance, the epicenter distance varies around 100 km of the epicenter distance. You can see that there are many.

6 and 7 are diagrams showing a comparison of the accuracy of the epicenter distance estimated by the method of the present embodiment and the epicenter distance estimated by the conventional method of Patent Document 1. FIG. FIG. 6 shows the accuracy of the epicenter distance estimated by the method of the present embodiment, and FIG. 7 shows the accuracy of the epicenter distance estimated by the conventional method of Patent Document 1. Here, f (θ _inc ) = sin (θ _inc ) is applied as the function f (θ _inc ) of the incident angle θ _inc in the equation (2) of the present embodiment.

  As for the accuracy of the estimated epicenter distance, log estimation Δ-log true Δ is obtained, and the closer this value is to 0, the better the accuracy.

  It can be seen that graphs are gathered closer to 0 in FIG. 6 than in FIG. The actual logarithmic error is that the epicenter distance estimated by the method of the conventional patent document 1 in FIG. 7 is 0.40, whereas the epicenter distance estimated by the method of the present embodiment in FIG. 6 is 0.32. The one estimated by the method of the present embodiment can be estimated with higher accuracy.

  In this way, the introduction of the correction term based on the incident angle θ improves the epicenter distance estimation accuracy, and in particular, improves the epicenter distance estimation accuracy at observation points close to the epicenter that is important for early earthquake parameter estimation. it can.

  Next, a second embodiment will be described. FIG. 8 is a diagram illustrating the epicenter distance estimation system of the second embodiment. In the figure, 100 is an epicenter distance estimation system, 101 is a data center, 102 is a center communication unit, 103 is a center processing unit, 104 is a centering buffer as a center storage means, and 105 is a center data record as a center storage means. Device. As for the seismometer 1, the same one as in the first embodiment is used.

In the present embodiment, in the data center 101, the center communication unit 102 transmits / receives earthquake early warnings and seismic wave information from each seismometer, and the centering buffer 104 or the center data recording device 105 of the center processing unit 103 The time series data of the initial movement part is stored. Then, the center processing unit 103 takes the absolute value of the time series data of the centering buffer 104 or the center data recording device 105, calculates the envelope, and sets the time when the earthquake is detected as the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
Fitting to the envelope, obtaining the coefficient B, applying an ellipsoid to the particle trajectory of the seismic motion from the time series data of the initial motion part of the seismic wave, and the direction of the epicenter as seen from the observation point by principal component analysis to obtain the direction of the maximum principal axis Then, the incident angle θ _inc is obtained, and the coefficient B and the incident angle θ _inc are expressed by the following equation: log Δ = C ₁ · log B + C ₂ · f (θ _inc ) + C ₃ (2)
However, C ₁ , C ₂ and C _{3 are} statistically determined constants, and f (θ _inc ) is applied to a function of incident angle θ _inc to determine the epicenter distance.

  The epicenter distance estimation system 100 includes a seismometer 1 that transmits and receives earthquake information to and from the data center 101, and the data center 101 transmits the epicenter distance to the seismometer 1 and the like by the center communication unit 102.

  In this way, the epicenter distance estimation system 100 processes the earthquake early warning and the information of the seismic wave from each seismometer 1 in the data center 101 as in this embodiment, and transmits it to each seismometer 1 etc. The burden on the total 1 and the like is reduced, and the seismometer 1 and the like can be downsized.

It is a figure which shows the seismometer of 1st Embodiment. FIG. 6 is a diagram showing a modification of the embodiment of FIG. It is a flowchart figure of estimation of the epicenter distance of 1st Embodiment. It is a conceptual diagram of estimation of an incident angle. It is a figure which shows the earthquake data applied by the comparison with this embodiment and a prior art. It is a figure which shows the accuracy of the epicenter distance estimated by the method of this embodiment. It is a figure which shows the precision of the epicenter distance estimated by the method of the conventional patent document 1. FIG. It is a figure which shows the epicenter distance estimation system of 2nd Embodiment. It is a figure which shows the relationship between epicenter distance and epicenter distance.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Seismograph, 2 ... Communication part, 3 ... Measurement part, 31 ... Sensor, 32 ... A / D converter, 4 ... Processing part, 41 ... Processing apparatus, 42 ... Ring buffer, 43 ... Data recording apparatus, 5 ... Clock unit, 6 ... Power supply unit, 7 ... GPS antenna, 20 ... Communication device, 30 ... Measurement device, 100 ... Vibration data recording system, 101 ... Data center, 102 ... Center communication unit, 103 ... Center processing unit

Claims (3)

Detection means for detecting seismic waves;
Storage means for storing time series data of the initial motion part of the seismic wave;
The absolute value of the time series data in the storage means is taken, the envelope is calculated, and the time when the earthquake is detected is the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope to obtain the coefficient B,
_{Find the} incident angle θ _inc from the time series data of the initial motion part of the seismic wave,
The coefficient B and the incident angle θ _inc are expressed by the following equation: log Δ = C ₁ · log B + C ₂ · f (θ _inc ) + C ₃ (2)
Where C ₁ , C ₂ and C _{3 are} statistically determined constants,
f (θ _inc ): An epicenter distance estimation apparatus comprising: a processing unit that is applied to a function of an incident angle θ _inc to obtain an epicenter distance. A center communication unit that transmits and receives seismic wave information,
Storage means for storing time series data of the initial motion part of the seismic wave;
The absolute value of the time series data in the storage means is taken, the envelope is calculated, and the time when the earthquake is detected is the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope to obtain the coefficient B,
_{Find the} incident angle θ _inc from the time series data of the initial motion part of the seismic wave,
The coefficient B and the incident angle θ _inc are expressed by the following equation: log Δ = C ₁ · log B + C ₂ · f (θ _inc ) + C ₃ (2)
Where C ₁ , C ₂ and C _{3 are} statistically determined constants,
f (θ _inc ): a center processing unit that applies the function of the incident angle θ _inc to obtain the epicenter distance;
A data center having
A seismometer that transmits and receives earthquake information to and from the data center;
The epicenter distance estimation system, wherein the data center transmits the epicenter distance to the seismometer by the center communication unit. Take the absolute value of the time series data of the initial motion part of the seismic wave, calculate the envelope, the time when the earthquake was detected as the time origin (t = 0),
y (t) = Bt · exp (−At) (1)
To the envelope to obtain the coefficient B,
_{Find the} incident angle θ _inc from the time series data of the initial motion part of the seismic wave,
The coefficient B and the incident angle θ _inc are expressed by the following equation: log Δ = C ₁ · log B + C ₂ · f (θ _inc ) + C ₃ (2)
Where C ₁ , C ₂ and C _{3 are} statistically determined constants,
f (θ _inc ): An epicenter distance estimation method characterized in that it is applied to a function of an incident angle θ _inc to obtain an epicenter distance.

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