JPH0263193B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an S wave detection device that detects S waves following P waves of seismic waves in real time in a disaster prevention system that detects earthquakes and takes disaster prevention measures. It is.

(Prior art) Conventionally, as a technology in this field, there has been a To detect S waves, store the seismic waveform data, recall the memorized seismic waveform data when the earthquake ends, and detect the S wave by assuming that the time immediately before the maximum value is the arrival time of the S wave. was.

(Problem to be solved by the invention) However, with this method, S
In order to perform the wave detection operation, several tens of seconds are required after the arrival of the S wave.
The arrival time of the S wave was not known until several seconds had passed. For this reason, there is a delay in determining whether the earthquake is dangerous or not, making it difficult to immediately take appropriate disaster prevention measures, and it is difficult to detect an earthquake before the S wave arrives. In the case of a system that issues a warning to determine whether or not the earthquake in question poses a danger (for example, a Shinkansen anti-seismic train protection device), the system issues a warning based solely on the magnitude of the amplitude. It also had the drawback of falsely issuing an alarm when there was a tremor.

(Means for Solving the Problems) The present invention has been made to solve these drawbacks. ), a second means for calculating a smoothed value of the horizontal motion component, a third means for calculating the epicenter direction, and a reduction in the amplitude ratio obtained by the first means; The increase in the smoothed value obtained by the second means and the third means
At least 1 sudden change in epicenter direction obtained by means of
This is an S-wave detection device comprising a fourth means for detecting the arrival of an S-wave by detecting the arrival of an S-wave.

(Operation) According to the present invention, as described above, the amplitude ratio of the vertical motion component and the horizontal motion component, the direction of arrival of the seismic wave, and the smoothed values of the vertical motion component and the horizontal motion amplitude are constantly calculated and stored based on the seismograph data. However, since the device is equipped with means for monitoring these data, it is possible to detect the arrival of S waves in real time by increasing the smoothing value, decreasing the amplitude ratio, and changing the arrival direction by the means. can. As a result, the epicenter distance can be determined from the initial tremor duration, and more accurate and effective disaster prevention measures can be taken.

Therefore, the above-mentioned problem can be eliminated.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 indicates the vertical direction, east-west direction,
A sensor that detects three components of ground motion in the north-south direction, 2 an amplifier that amplifies the detection signal from sensor 1, 3 a buffer amplifier, and 4 a control processing device that processes the three components of ground motion and detects the arrival of S waves. , 5 is a device that generates accurate time information. The control processing device 4 includes an epicenter azimuth calculator 11, an upper/lower horizontal amplitude ratio calculator 12, a seismic wave detector 13, and a sampler 14.

6 is a device that displays the results detected by the control processing device 4; 7 is a communication control device that transmits the results detected by the control processing device 4 via the communication line 8.

Next, the operation of the embodiment shown in the block diagram of FIG. 1 will be explained. The sensor 1 detects ground motion at a point where it is constantly installed, converts this into an electrical signal, and sends it to the control processing device 4.

The control processing device 4 inputs information on each component of the ground motion detected by the sensor 1 and constantly sent to the sampler 14 at predetermined time intervals (for example, 1/50 to 1/150 seconds), and calculates the past information. The offset level, which is the direct current component of the input data, is calculated from the average value of the sampling information for each batch. This offset level is constantly updated based on sampling information obtained from time to time. Next, the value obtained by removing the offset level from the sampled values of the three-component ground motion information in the vertical direction, east-west direction, and north-south direction detected by the sensor 1 and sent from time to time, that is, x ₁ (t), Based on x ₂ (t), x ₃ (t), noise levels NX ₁ , NX ₂ , NX ₃ and exponential smoothing value ax ₁
(t), ax ₂ (t), and ax ₃ (t). The noise level is the average value of |x _i (t)|, and is used to determine level A for detecting seismic waves. Exponential smoothing value ax _i (t)
is calculated using the following formula.

ax _i (t)=ax _i (t-1)×α _i +x _i2 (t) α _i is a constant of about 0.9. The sampler 14 performs x _i
(t), ax _i (t) and NX _i by the epicenter azimuth calculator 11, the vertical and horizontal amplitude ratio calculator 12, and the seismic wave detector 13.
Send to.

The epicenter azimuth θ(t) is calculated as follows by the epicenter azimuth calculator 11, and θ(t) for about the past 3 seconds is stored.

The exponential smoothing value x _UDNS of the product of vertical motion and north-south motion is calculated by the following formula.

x _UDNS (t) = x _UDNS (t-1) x α + x ₁ (t) x x ₃ (t) The exponentially smoothed value x _UDEW of the product of vertical motion and east-west motion is calculated by the following formula.

x _UDEW (t) = x _UDEW (t-1) x α + x ₁ (t) x x ₂ (t) The epicenter azimuth θ(t) is calculated by the following procedure. First, calculate the angle θ ₀ (t) from east to north using the formula θ ₀ (t)=tan ^-1 (x _UDNS (t)/x _UDEW (t)). Next, since θ ₀ (t) is in the range of -90° to 90°, it is divided into the following four quadrants based on the signs of x _UDNS (t) and x _UDEW (t), see FIG. 2.

_{x UDNS _}
~360°) and determine θ(t). When calculating the arctangent (tan ^-1 ), it is more time-consuming to memorize numerical values corresponding to 0 to 90° in memory and compare them to find the values in degrees, rather than solving the approximate equation each time. It saves money.

The epicenter azimuth calculator 11 calculates the epicenter azimuth θ(t),
Seismic wave detector 1 detects the average value (t) of the past 3 seconds or so.
Send to 3.

FIG. 4 is an example of calculating θ(t). When an earthquake wave arrives, θ(t) changes rapidly and indicates the epicenter direction.

The vertical horizontal amplitude ratio calculator 12 calculates the amplitude ratio (VH) between the vertical motion amplitude and the horizontal motion amplitude using the following equation, and stores the VH(t) for about the past 3 seconds.

The vertical horizontal amplitude ratio calculator 12 calculates the VH (t) and the average value (t) of the past 3 seconds using the seismic wave detector 1.
Send to 3.

As shown in Figure 4, when an earthquake wave arrives, VH(t)
increases, and when the S wave arrives, VH(t) decreases. Even if the amplitude of the P wave is too small to be detected and it is detected as an earthquake wave only when the S wave arrives, VH(t) will fall as shown in Figure 5, so it can be identified as an S wave. be able to.

The seismic wave detector 13 detects the exponentially smoothed value hx(t) of the current horizontal motion component (here, hx(t)=hx(t-1)×α
+√ ₂ ² () + ₃ ² ()) is the exponential smoothing value 3 seconds ago
It is constantly monitored to see if it exceeds twice ax1 (t-3 seconds).

(1) If it exceeds twice, it is determined that an S wave has arrived, and the following processing is performed to confirm whether it is an S wave.

(2) Average value of V/H for 1 second immediately before the time when condition (1) is met (VHB) and average value of V/H for 1 second immediately after satisfying condition (1) (VHA) Calculate.

(3) Must be VHA < VHB.

(4) Must be VHA<0.9.

(5) Must be VHB−VHA>0.2.

(6) Calculate the average value of the azimuth (AZB) for 1 second immediately before the time when the condition (1) is satisfied and the average value of the azimuth (AZA) for the 1 second immediately after the time when the condition (1) is satisfied.

(7) The difference between AZB and AZA must be 10 degrees or more.

(8) After satisfying the conditions in (1) above, (3), (4), (5),
If all conditions (7) are satisfied, it is determined that the S wave has arrived. If any of the conditions (3), (4), (5), and (7) above are not satisfied, it is not determined that an S wave has arrived.

FIG. 3 shows a schematic flow of these control processes.

(Effects of the Invention) As explained above, according to the present invention, the arrival of the S wave can be detected in real time, the time from P to S (initial movement duration, P to S time) can be immediately detected, You can know the epicenter distance. Therefore, it has become possible to take more accurate and effective disaster prevention measures.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 shows θ ₀ (t) in the control processing device of FIG.
An explanatory diagram for converting from to θ(t), Fig. 3 is a schematic flow chart of control processing, Fig. 4 is an example of detecting the arrival of an S wave from the seismic waveform obtained in the example, Fig. 5 cannot be considered because the P wave amplitude is small,
An example of an earthquake where an earthquake was detected as an S wave for the first time when an S wave arrived, but it was detected as an S wave. Figure 6 shows an example in which it was determined that no S wave was included based on the seismic waveform obtained in the example. This is an example. DESCRIPTION OF SYMBOLS 1... Sensor, 2... Amplifier, 3... Buffer amplifier, 4... Control processing device, 5... Time information generation device, 6... Display device, 7... Communication control device,
8...Communication line, 11...Epicenter direction calculator, 12
... Vertical horizontal amplitude ratio calculator, 13 ... Seismic wave detector, 14 ... Sampler.

Claims (1)

[Claims] 1 (a) a first means for calculating the amplitude ratio of the vertical motion component and the horizontal motion component; (b) a second means for calculating the smoothed value of the horizontal motion component; (c) (d) a decrease in the amplitude ratio obtained from the first means; an increase in the smoothed value obtained from the second means; and (d) a decrease in the amplitude ratio obtained from the second means; An S-wave detection device comprising a fourth means for detecting the arrival of an S-wave by detecting at least one sudden change in epicenter direction.