JP6441144B2 - Major motion detection method of earthquake - Google Patents

Description

  The present invention relates to an earthquake main motion determination method for determining whether or not the shaking at the time of detection is due to a main motion (S wave) from an observation waveform detected by a seismometer installed at a determination target point when an earthquake occurs. It is about.

  When an earthquake occurs, using the information on the P wave that arrives first, the magnitude of the S wave that arrives later is predicted, and in the alarm system immediately before an earthquake for delivering an alarm or a device stop signal in advance, at a certain time It is important to determine whether the observed seismic wave is a P wave or an S wave in order to ensure the prediction accuracy.

  That is, if the observed ground motion of the P wave is erroneously determined to be due to the S wave, it is not possible to predict a stronger shake due to the actual S wave that arrives thereafter, and as a result, an alarm or device stop signal Delivery may be delayed. Conversely, if the observed S-wave ground motion is still erroneously determined to be due to a P-wave, it will be predicted that there will be a stronger shaking after that, and there is no need to issue a warning or the like. On the other hand, there is a possibility of delivering an alarm or a device stop signal.

  As a conventional means for detecting the S wave in the above-mentioned earthquake motion, for example, in Patent Document 1 below, the arrival of the S wave is determined based on the idea that the vertical motion is dominant in the P wave and the horizontal motion is dominant in the S wave. An S-wave detection device has been proposed.

  The S-wave detection method in this S-wave detector is such that the ratio (V / H) of the smoothed waveform of the vertical and horizontal movements observed at the time of the earthquake falls below a preset S-wave determination threshold. It is determined that the S wave has arrived.

  However, in the conventional S wave determination method, when the S wave determination threshold is appropriately set for the observation waveform of the direct earthquake shown in FIG. 5, the observation waveform of the trench earthquake shown in FIG. For an earthquake in which the vertical movement tends to be less prominent than the horizontal movement in the initial movement of the P wave, the P wave may be erroneously determined as an S wave.

  As described above, even if an S-wave determination threshold is set for the ratio of vertical motion to horizontal motion (V / H) assuming an earthquake of a specific observed waveform, the observed waveform having different degrees of superiority of horizontal motion with respect to vertical motion There was a problem that it was not possible to correctly evaluate the earthquake.

Japanese Patent Application Laid-Open No. 61-076975

  The present invention has been made in view of the above circumstances, and the S wave of the earthquake can be obtained with high accuracy even for earthquakes having observed waveforms having different degrees of horizontal movement with respect to the vertical movement of the P wave and the S wave. It is an object of the present invention to provide a method for determining major motion of an earthquake that can be determined.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a value indicating the magnitude of the horizontal (H direction) and vertical (V direction) seismic motion observed every moment at the determination target point when an earthquake occurs. The HV curve in the HV plane is obtained from (H, V), and the main motion (S wave) of the earthquake is determined from the non-linearization of the HV curve.

  According to a second aspect of the present invention, in the first aspect of the invention, the values (H, V) are accelerations, and a waveform obtained by smoothing the absolute values of the accelerations in the H and V directions is obtained. The HV curve is obtained by projecting onto the HV plane.

Furthermore, in the invention described in claim 3, in the invention described in claim 2, a plurality of storage threshold values that are sequentially higher are set in advance for the acceleration value in the H direction, and the acceleration in the H direction is For the above values (H _K , V _K ) (k = 1, 2, 3,...) When the storage threshold is exceeded, (total V / H ratio) = V _K / H _K and (section V / H ratio) = (V _K -V _K-1 ) / (H _K -H _K-1 ) is calculated, and the above (section V / H ratio) / the above (total V / H ratio) is determined in advance. The case where it falls below the use threshold is determined as the S wave.

  1A shows a waveform obtained by smoothing the ground motion waveform of the direct earthquake shown in FIG. 5 with acceleration smoothing. FIG. 1B shows an HV curve obtained from the acceleration smoothing waveform. It is shown. FIG. 2A shows a waveform obtained by smoothing the ground motion waveform of the trench-type earthquake shown in FIG. 6, and FIG. 2B shows an HV obtained from the acceleration smoothed waveform. A curve is shown.

  As can be seen in FIG. 1B and FIG. 2B, it can be seen that the HV curve in any earthquake motion draws a bilinear curve that becomes nonlinear when the S wave arrives.

  And according to invention of any one of Claims 1-3, the value (H which shows the magnitude | size (H direction) of the horizontal direction (H direction) and the vertical direction (V direction) observed every moment in the determination point V), the above HV curve is obtained, and the S wave of the earthquake is determined from its non-linearization, so that the earthquakes having observed waveforms having different degrees of horizontal motion with respect to the vertical movement of the P wave and S wave are different from each other. However, the S wave of the earthquake can be determined with high accuracy.

(A) shows the waveform obtained by smoothing the ground motion waveform of the direct earthquake shown in FIG. 5, and (b) shows the HV curve obtained from the acceleration smoothed waveform. . (A) shows a waveform obtained by smoothing the ground motion waveform of the trench-type earthquake shown in FIG. 6, and (b) shows an HV curve obtained from the acceleration smoothed waveform. . It is a figure for demonstrating the method of determining non-linearization from a HV curve. It is a figure which shows the result of having performed S wave determination using one Embodiment of this invention with respect to the seismic-motion waveform of FIG. It is a figure which shows the result at the time of applying the conventional S wave determination method with respect to the ground motion waveform of a direct type earthquake. It is a figure which shows the result at the time of applying the conventional S wave determination method with respect to the ground motion waveform of a trench type earthquake.

Hereinafter, based on FIGS. 1-4, one Embodiment of the S wave determination method of the earthquake motion which concerns on this invention is described.
First, in the event of an earthquake, the horizontal (H direction) and vertical (V direction) accelerations are measured momentarily by a seismometer installed at the site, such as a factory that is the target for determination, and in parallel with this, Smooth the ground motion waveform of the measured acceleration.

This acceleration smoothing waveform is calculated by the following equation.
Horizontal movement: H _i = H _i-1 × α + (x _i ² + y _i ² ) ^1/2 × (1-α)
Vertical movement: V _i = V _i-1 × α + | z _i | × (1-α)
Here, x _i and y _i are acceleration horizontal motion components, z _i is an acceleration vertical motion component, and α is an exponential smoothing coefficient.

FIG. 1A and FIG. 2A are obtained by smoothing the ground motion waveforms shown in FIG. 5 and FIG. 6 using the above equations.
Next, an HV curve is obtained by projecting the acceleration smoothing waveform thus obtained on the HV plane. FIG. 1B and FIG. 2B are HV curves obtained by projecting the acceleration smoothing waveforms of FIG. 1A and FIG. 2A onto the HV plane, respectively.

Then, it is determined whether the HV curve is non-linear. Various mathematical methods can be adopted as the non-linear determination method.
In the present embodiment, a plurality of storage threshold values that are successively higher are set in advance for the acceleration value H in the H direction. Incidentally, it is preferable to set the plurality of storage thresholds so as to sequentially increase at equal intervals on the logarithmic axis.

Then, the increase in the acceleration value H at the time of the earthquake, to save the above value when sequentially exceeds the above-mentioned storage threshold _{(H K, V K) (} k = 1,2,3, ...), of these Using the acceleration values (H _K , V _K ), as shown in FIG. 3, (overall V / H ratio) and (section V / H ratio) are calculated.

Here, (the entire V / H ratio), a rate of increase of V _K for H _K up when Save threshold H _K from the time of the earthquake, (section V / H ratio), preceding (V _K -V _K-1 ) increase rate with respect to (H _K -H _K-1 ) from when the storage threshold H _K-1 is stored until the storage threshold H _K is stored.

That is, (total V / H ratio) and (section V / H ratio) are calculated by the following equations, respectively.
(Overall V / H ratio) = V _K / H _K
(Section V / H ratio) = (V _K −V _K−1 ) / (H _K −H _K−1 )

  Next, the above (section V / H ratio) / the above (total V / H ratio) is calculated, and when the obtained value exceeds a preset threshold for determination, it is determined as a P wave, and when it is below, the above S wave judge.

4 calculates an acceleration smoothing waveform from the observed waveform using the S-wave determination method of the present embodiment described above for the observed waveform of the trench-type earthquake shown in FIG. Ratio) = V _K / H _K and (section V / H ratio) = (V _K −V _K−1 ) / (H _K −H _K−1 ) to (section V / H ratio) / above (total V / H ratio) is calculated, and the result of the determination of the P wave and the S wave compared with a preset threshold for determination (0.95 in the present embodiment) is shown.

  As can be seen from FIG. 4, according to the present embodiment, it is possible to appropriately determine the S wave even for the observation waveform of a trench-type earthquake that has been erroneously determined by the conventional determination method.

  As described above, according to the seismic motion S wave determination method having the above-described configuration, the acceleration waveform of the horizontal (H direction) and vertical (V direction) seismic motion observed every moment in the field is smoothed and obtained. The obtained acceleration smoothing waveform is projected onto the HV plane to obtain an HV curve, and the S wave of the earthquake is determined from the non-linearization in the HV curve. Even for earthquakes having observed waveforms with different degrees of horizontal motion relative to vertical motion, the S wave of the earthquake can be determined with high accuracy.

Further, in the present embodiment, as acceleration values for calculating (total V / H ratio) and (section V / H ratio), acceleration values H in the H direction are previously equally spaced on the logarithmic axis. A plurality of increasing storage threshold values are set, and when the acceleration value H increases and sequentially exceeds the storage threshold value (H _K , V _K ) (k = 1, 2, 3,...) Is saved.

As a result, since the storage threshold interval (H _K -H _K-1 ) having the same ratio is always set for the acceleration value H _K , stable (section V / H ratio) against large and small seismic waves. ) Is obtained, and the probability of erroneous determination can be reduced.

Claims (3)

  From the values (H, V) indicating the magnitudes of horizontal (H direction) and vertical (V direction) ground motions observed at each point of judgment at the time of the occurrence of the earthquake, the HV curve on the HV plane. And determining the main motion (S wave) of the earthquake from the non-linearization of the HV curve.   The values (H, V) are accelerations, and the HV curve is obtained by projecting on the HV plane a waveform obtained by smoothing the absolute values of the accelerations in the H and V directions. The method for determining a major motion of an earthquake according to claim 1. With respect to the acceleration value in the H direction, a plurality of storage threshold values that are sequentially higher are set in advance, and the values when the acceleration in the H direction sequentially exceeds the storage threshold value (H _K , V _K ) ( For k = 1, 2, 3,..., (overall V / H ratio) = V _K / H _K and (section V / H ratio) = (V _K −V _K−1 ) / (H _K −H _{K -1} ) is calculated, and when the (section V / H ratio) / (total V / H ratio) falls below a predetermined threshold for determination, it is determined as the S wave. The main motion judgment method of earthquake described in.

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