JP3695579B2 - Epicenter distance and magnitude estimation method and apparatus therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for estimating the distance from an observation point to the epicenter (the epicenter distance) and the magnitude of the earthquake (magnitude) within a few seconds from the detection of the earthquake, and an apparatus for the same Is.
[0002]
[Prior art]
Traditionally, to estimate the epicenter distance and magnitude,
(A) Find the location of the epicenter from multi-point observation data and calculate the epicenter distance to each observation point.
(B) Estimating the magnitude from the epicenter distance, amplitude value, period, vibration duration, etc.
(C) Estimate the magnitude from the period of the initial motion at one observation point, and estimate the epicenter distance, depth, and epicenter distance from this magnitude and the amplitude of the initial motion.
There are methods.
[0003]
[Problems to be solved by the invention]
However, the methods (a) and (b) described above are high in accuracy with conventional methods, but estimation takes several minutes after earthquake detection.
[0004]
The method (c) described above is a method of estimating from the data of the initial motion part of one observation point before the main motion of the earthquake (a large vibration causing damage) reaches the observation point. However, the estimation accuracy is not so high, and there is a problem that the estimation accuracy is particularly bad for a remote earthquake or a deep earthquake.
[0005]
In view of the above situation, the present invention focuses on the characteristics of the waveform shape of the initial motion part that changes characteristically depending on the epicenter distance and the difference in magnitude, quantifies the waveform shape by fitting parameters with several simple functions, It is an object of the present invention to provide an epicenter distance and magnitude estimation method and apparatus capable of estimating the epicenter distance and magnitude from the obtained parameters.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] on features of the waveform shape of the seismic wave initial portion derived from seismograph, quantified by fitting the waveform shape functions, from the parameters obtained, epicentral distance and estimate the epicentral distance and magnitude A magnitude estimation method, wherein digital waveform data (time-series data) of an initial seismic wave portion obtained from the seismometer is stored in a memory, an offset of the time-series data is removed, and an absolute value of the time-series data is expressed as V (t) ungated [wherein, t is time (seconds)], as the time origin time of detecting the seismic (t = 0), from the time origin, the number of function for a few seconds of data y = Bt · e ^- fitting the ^at, and V (t) = Bt exp ( -At) ( where, B is a parameter related to time variation of the initial amplitude of the seismic wave, a is related to the maximum amplitude of initial partial parameter ), Taking the logarithm of both sides of the above equation to obtain a log [V (t) / t] = logB-A · loge · t , thereby, the parameter A, B and linearization, this parameter A, B is calculated by the parameter calculation means using a normal least square method, and the epicenter distance and magnitude estimation means obtains the epicenter distance from the parameter B, and the obtained epicenter distance and the maximum amplitude value within the reference time, Alternatively, the magnitude is obtained from the parameter A.
[0007]
[2] In the epicenter distance and magnitude estimation device, the seismometer, the memory for storing the digital waveform data (time series data) of the initial motion part of the seismic wave obtained from the seismometer, and the offset of the time series data are removed, The absolute value of the time-series data is V (t) [where t is time (seconds)], and the time at which the earthquake is detected is the time origin (t = 0). ^Fit function y = Bt · e ^−At and set 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) ), Taking the common logarithm of both sides of the above equation to obtain log [V (t) / t] = logB−A · log · t, thereby linearizing the parameters A and B, the parameters A and B The normal A parameter calculating means for calculating using the least squares method, the seek epicenter distance from the parameter B, epicentral distance and obtaining the magnitude of the maximum amplitude value of the obtained the epicenter distance and the reference time, or before Kipa parameters A Magnitude estimation means.
[0008]
[ 3 ] The epicenter distance and magnitude estimation device according to [ 2 ], further comprising condition determination means for determining whether or not an earthquake of a magnitude greater than or equal to a predetermined magnitude has occurred within a predetermined epicenter distance. And
[0009]
[ 4 ] The epicenter distance and magnitude estimation apparatus according to [ 3 ] above, further comprising information sentence sending means for sending early detection information.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0011]
Let the time series data of the seismic waveform be v (t). Furthermore, the absolute value of this time series data v (t) is V (t). Here, t represents time (second).
[0012]
First, the time at which an earthquake is detected is set as the time origin (t = 0), and a simple function is applied to data for several seconds therefrom. Here, the following equation (1) is used as the function form. If V (t) varies greatly over time, the function is fitted after smoothing V (t) by an appropriate method.
[0013]
V (t) = Bt exp (−At) (1)
Here, B is a parameter relating to the temporal change in the initial motion amplitude of the seismic waveform, and A is a parameter relating to the maximum amplitude of the initial motion portion, and these are hereinafter referred to as shape parameters. Taking the common logarithm of both sides of the above equation (1), the unknown parameter is linearized as in the following equation (2), so that the shape parameter can be calculated using a normal least square method.
[0014]
log [V (t) / t] = logB−A · log · t (2)
As a result of obtaining the shape parameters A and B of the initial motion part for a lot of seismic waveform data using the above method, it was found that the parameter B had a good correlation with the epicenter distance.
[0015]
It was also found that the relationship between parameter B and epicenter distance does not depend on magnitude. Therefore, if the correlation between the parameter B and the epicenter distance is formulated, the epicenter distance Δ can be obtained from the shape parameter B of the seismic wave initial motion part.
[0016]
Once the epicenter distance is obtained, the magnitude can be formulated from the formula using the epicenter distance and the maximum amplitude that are generally used. It is also possible to formulate an equation using the shape parameter A instead of the maximum amplitude.
[0017]
It has been confirmed that the estimation accuracy of the magnitude estimated by the above method is considerably improved as compared with the method of estimating using the period of the initial movement portion described above.
[0018]
From the above, according to the present invention, it is possible to accurately calculate the epicenter distance and the magnitude within a few seconds from the detection of the earthquake, and thus determine the harm of the earthquake before the main motion of the earthquake reaches the observation point. It can be used effectively in the field of earthquake disaster prevention.
〔Example〕
FIG. 1 is a block diagram of an epicenter distance and magnitude estimation apparatus according to the present invention, and FIG. 2 is a process flowchart of the epicenter distance and magnitude estimation.
[0019]
In these figures, 1 is a seismometer, 2 is a communication line, 10 is a control processing device, 11 is an anti-aliasing filter (low-pass filter), 12 is an A / D converter, 13 is a waveform recording unit, 14 is a memory, 15 Is a parameter calculation unit, 16 is an epicenter distance and magnitude estimation unit, 17 is a condition determination unit, 18 is an information sentence transmission unit, 19 is a GPS clock, 20 is a status display device, and 21 is a modem.
[0020]
The epicenter distance and magnitude estimation method will be described with reference to the flow shown in FIG.
[0021]
(1) Information from the seismometer 1 is taken into the control processor 10 and acquired as digital waveform data in the memory 14 (step S1).
[0022]
(2) Therefore, the parameter calculator 15 removes the offset (step S2), and then takes the absolute value of the data. At this time, if the absolute value is less than or equal to a certain reference value, it is forcibly set to the minimum reference value (step S3). Next, the smoothing (e.g., take the envelope of the waveform) (Step S4). Next, fitting is performed with y = Bt · e ^−At to obtain parameters (coefficients) A and B (step S5).
[0023]
(3) Next, the epicenter distance and magnitude estimation unit 16 obtains the epicenter distance from the obtained parameter B (step S6). Based on the epicenter distance, the magnitude M is estimated from the maximum amplitude value within the reference time or the obtained parameter A (step S7).
[0024]
(4) Next, the condition determining unit 17 determines whether or not an earthquake having a magnitude greater than or equal to a predetermined epicenter distance has occurred (step S8).
[0025]
(5) If YES in step S8, the information sentence sending unit 18 transmits early detection information (step S9).
[0026]
FIG. 3 is a diagram showing an example of fitting a simple function to an actual seismic wave, FIG. 3 (a) is an actual initial motion wave (P wave), and FIG. 3 (b) is an example of fitting the simple function. FIG.
[0027]
FIG. 4 shows the correlation between the parameter B and the epicenter distance Δ by performing the same fitting on a lot of earthquake data, obtaining the shape parameter of the initial motion part. In this figure, the horizontal axis indicates the epicenter distance (km), and the vertical axis indicates logB.
[0028]
In this figure, the size of the mark is proportional to the magnitude M, the maximum corresponds to M8.1, and the minimum corresponds to M4.5. From FIG. 4, it can be seen that there is a negative correlation between the parameter B and the epicenter distance Δ, and this correlation does not depend on the magnitude. Therefore, by formulating this correlation, the epicenter distance can be estimated using only the parameter B.
[0029]
The form of the estimation formula should not be limited to one, but examples include the following forms.
[0030]
log Δ = α ₁ logB + α ₂ (3)
Δ = α ₁ / log B + α ₂ (4)
The magnitude M is a formula using the epicenter distance and the maximum amplitude V _max that are generally used.
M = β ₁ log V _max + β ₂ log Δ + β ₃ (5)
Therefore, it can be formulated by the parameter A or the maximum amplitude V _max and the parameter B, but this form is not limited to one, and the following form can be considered as an example.
[0031]
M = γ ₁ A + γ ₂ logB + γ ₃ (6)
M = γ ₁ log V _max + γ ₂ log B + γ ₃ (7)
M = γ ₁ A + γ ₂ log (log B) + γ ₃ (8)
M = γ ₁ log V _max + γ ₂ log (log B) + γ ₃ (9)
Here, α ₁ , α ₂ , β ₁ , β ₂ , β ₃ , γ ₁ , γ ₂ , and γ ₃ are parameters determined by statistical processing from a large number of earthquake data.
[0032]
FIG. 5 compares the epicenter distance estimated using Equation (3) with the actual epicenter distance. In this figure, the horizontal axis indicates the estimated epicenter distance (km), and the vertical axis indicates the actual epicenter distance (km). FIG. 6 is a comparison of the magnitude estimated using Equation (7) and the actual magnitude. In this figure, the horizontal axis represents the estimated magnitude, and the vertical axis represents the actual magnitude.
[0033]
As can be seen from these figures, the error of the magnitude estimated by the present invention from the actual magnitude is about 1 at most, and it can be seen that it is estimated with high accuracy.
[0034]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention.
[0035]
【The invention's effect】
As described above in detail, according to the present invention, paying attention to the characteristics of the waveform shape of the initial motion part that changes characteristically depending on the epicenter distance and the difference in magnitude, this waveform shape is a simple parameter with several parameters. It can be quantified by fitting with a function, and the epicenter distance and magnitude can be estimated from the obtained parameters.
[Brief description of the drawings]
FIG. 1 is a block diagram of an epicenter distance and magnitude estimation device according to the present invention.
FIG. 2 is a process flowchart of epicenter distance and magnitude estimation according to the present invention.
FIG. 3 is a diagram showing an example of fitting a simple function to an actual seismic wave.
FIG. 4 is a diagram showing a correlation between a parameter B and an epicenter distance Δ.
FIG. 5 is a diagram comparing the estimated epicenter distance with the actual epicenter distance.
FIG. 6 is a diagram comparing the estimated magnitude with the actual magnitude.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Seismometer 2 Communication line 10 Control processing apparatus 11 Anti-aliasing filter 12 A / D converter 13 Waveform recording part 14 Memory 15 Parameter calculation part 16 Epicenter distance and magnitude estimation part 17 Condition determination part 18 Information sentence transmission part 19 GPS clock 20 Status display device 21 Modem

Claims (4)

On features of the waveform shape of the seismic wave initial portion derived from seismograph, quantified by fitting the waveform shape functions, from the parameters obtained, epicentral distance and magnitude estimation method for estimating the epicentral distance and magnitude a is, the digital waveform data of seismic initial portion obtained from the seismometer (time series data) stored in the memory, to remove the offset of the time series data, the absolute value of the time series data V (t) ungated [wherein, t is time (seconds)], as the origin of the time of detecting the seismic time (t = 0), the said time origin, fitting the function number y = Bt · e ^-At a few seconds of data , (parameter where, B is related to the maximum amplitude of the time parameter relating to the change, a is initial portion of the initial amplitude of seismic waveforms) and V (t) = Bt exp ( -At), the formula Taking common logarithm of both sides, with the log [V (t) / t] = logB-A · loge · t , thereby, minimize the parameters A, B and linearization, the parameters A, B normal Calculated by the parameter calculation means using the square method, and the epicenter distance and magnitude estimating means obtains the epicenter distance from the parameter B. From the obtained epicenter distance and the maximum amplitude value within the reference time, or from the parameter A epicentral distance and magnitude estimation method and obtains the magnitude. (A) a seismometer;
(B) a memory for storing digital waveform data (time-series data) of the initial motion part of the seismic wave obtained from the seismometer;
(C) The offset of the time series data is removed, the absolute value of the time series data is V (t) [where t is time (seconds)], and the time when the earthquake is detected is the time origin (t = 0), the function y = Bt · e ^−At is applied to the data for a few seconds from the time origin, and V (t) = Bt exp (−At) (where B is the time variation of the initial amplitude of the seismic waveform) Parameter, A is a parameter related to the maximum amplitude of the initial movement portion), and logarithm logarithm of both sides of the above equation is taken to obtain log [V (t) / t] = logB−A · log · t, Parameter computing means for linearizing the parameters A and B and calculating the parameters A and B using a normal least square method;
(D) determine the epicenter distance from the parameter B, and and a maximum amplitude value, or before Kipa parameter Ru seek magnitude from A Shin central distance and the magnitude of the estimating means in the the obtained epicenter distance and the reference time Epicenter distance and magnitude estimation device. The epicenter distance and magnitude estimation apparatus according to claim 2, further comprising a condition determination means for determining whether or not an earthquake of a magnitude greater than or equal to a predetermined magnitude has occurred within a predetermined epicenter distance. And a magnitude estimation device. The epicenter distance and magnitude estimation apparatus according to claim 3 , further comprising information sentence sending means for transmitting early detection information.

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