JPS597950B2 - Earthquake initial motion detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device capable of detecting the initial motion of an earthquake.

In general, it is known that seismic motion includes P waves, which are components that vibrate near the ground surface in a nearly vertical direction, and S waves, which are components that vibrate in an almost horizontal direction. One of the important issues is to accurately know when P waves and S waves first respond.

Conventionally, in order to detect the initial motion of these waves, it has been estimated based on experience based on the obtained data, which has caused the problem that the exact time of the initial motion cannot be known.

The present invention aims to solve these five problems, and aims to provide an earthquake initial motion detection device that can objectively and accurately determine the initial motion of P waves and S waves. purpose.

For this reason, the earthquake initial motion detection device of the present invention includes a pair of vibration detectors arranged in the same plane including the vertical axis and symmetrically inclined with respect to the same vertical axis, and each of these vibration detectors A multiplication circuit connected to each output terminal of the vibration detector for mutually multiplying the detected values, and means for determining whether the product of the detected values obtained by the multiplication circuit is positive or negative are provided, and , characterized in that a correction means is provided for moving the vibration detector along its central axis in order to adjust and correct the operating center position of the vibration detector that has moved due to the inclination of the vibration detector. There is.

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
Figures 1 to 4 show an earthquake initial motion detection device as the first actual case. Figure 1 is an explanatory diagram schematically showing its arrangement, and Figure 2 shows its vibration detector. electrical circuit diagram,
3A to 3D are vector diagrams for explaining the effect, and FIGS. 4A to 4E are waveform diagrams for explaining the effect.

As shown in FIG. 1, a pair of moving coil type vibration detectors 2.3 are tilted so that they are arranged symmetrically and tilted by 45 degrees with respect to the vertical axis 1 within the same plane that includes the vertical axis 1. It is mounted on the base 4.

Each of the vibration detectors 2.3 mounted on the inclined base 4 in this manner is housed in a strong case and is buried underground so that it is not easily affected by noise vibrations.

Furthermore, the output terminals 2a and 3a of the vibration detectors 2 and 3 are connected to a multiplication circuit 5, which multiplies the detection values X and Y of these vibration detectors 2 and 3 with each other. The product X-Y can be obtained.

Further, on the output side of the multiplication circuit 5, a thousand stages 6 are provided for determining whether the product X-Y of the detection values X and Y obtained by the multiplication circuit 5 is positive or negative.

This 1,000-stage 6 has a product of X. A pen recorder that records the waveform of Y on recording paper, a pen recorder that records the waveform of Y, A display device that displays the waveform of the product X.Y on a cathode ray tube or the like, a sign discriminator including a comparator that determines whether the product Various types of computer systems can be considered, including a magnetic tape that magnetically records the Y waveform and then performs computer processing.

By the way, the vibration detector 2.3 used for earthquake observation is
Many have low natural frequencies, and are usually installed vertically or horizontally to detect vertical or horizontal vibrations.

When these vibration detectors 2.3 are arranged in an inclined manner as in this embodiment, in the case of horizontal motion, the force of gravity acts, causing the movable coil 7.8 to shift downward from the center of motion. ,
In the case of vertical motion, the gravitational component decreases and the moving coils 7, 8
may move upward and become unusable in either case.

Therefore, these vibration detectors 2 and 3 are provided with movable coils 7 and 7 in order to correct the gravity component caused by the inclination of the vibration detectors 2 and 3, that is, to correct the operation center position.
DC type correction coil 1 as a correction means for lowering 8 to an upper or lower neutral position along its central axis 9.10
1.12 are provided on each moving coil 7,8.

That is, each correction coil 11. 12 is a support spring 13
, 14, and are provided integrally with the movable coils 7, 8 supported by the correction coils 11. 12, as shown in FIGS. 1 and 2, DC power supplies 15 and 16 are connected to supply them with a constant bias current.

Furthermore, since the moving coils 7.8 with correction coils are arranged so as to fit into the annular gaps of the magnetic field generating members 17 and 18, when a current is passed through the correction coils in a predetermined direction, the moving coils 7.8 An electromagnetic force is generated that moves it to a neutral position.

The magnetic field generating members 17 and 18 include a yoke forming a frame thereof, a permanent magnet provided at the center of the yoke, and a pole piece disposed above the permanent magnet and forming an annular gap together with the yoke. It consists of

Since the earthquake initial motion detection device of the present invention is configured as described above, when detecting the initial motion of an earthquake, a bias current is passed through the mass correction coils 11 and 12 to move the movable coils 7 and 8 to the neutral position. Correct it.

In such a state, when an earthquake occurs, the movable coils 7 and 8 swing to cut off the magnetic field in the annular gap between the magnetic field generating members 17 and 18. The voltage signal X corresponding to this earthquake motion from
, Y are output, and these detected values X and Y are sent to the multiplication circuit 5.
After that, this product X-Y is inputted to a positive/negative discrimination stage 6 of a pen recorder or the like so that its positive/negative value can be determined.

By the way, P waves of seismic motion vibrate parallel to the direction of earthquake movement M, as shown by the symbol P in Figure 3 a and b, and S waves are:
As shown by the symbol S in Fig. 3c and d, these P and S waves vibrate at right angles to the traveling direction M, respectively.
When the actions shown in figures a to d occur, the vibration detectors 2 and 3 output detection values X and Y that depend on the component force vectors of vectors P and S, corresponding to each figure. ing.

Here, if we assume that the region where the vibration force acts on the P wave in the same direction as the seismic movement direction M is positive, and the region where it acts in the opposite direction is negative, then the detection values X and Y of each vibration detector 2 and 3 In the case of FIG. 3a, the signs are positive and positive, and the product X. Y also becomes positive, and in the case of Figure 3b, it becomes negative and negative, and the product X-Y becomes positive, and in the case of Figure 3C, it becomes negative and positive, and the product X-Y becomes negative, and the In the case of Figure 3 d, it is positive and negative, and the product X・
Y becomes negative.

Therefore, when each vibration detector 2.3 detects a P wave, the output of the multiplication circuit 5 becomes positive, and when it detects an S wave, it becomes negative, so it is necessary to determine whether the output value of the multiplication circuit 5 is positive or negative. This will tell you whether it is a P wave or an S wave, and from this you can know when the P and S waves start moving.

An example of this will be explained with reference to FIG. 4. The vibration detector 2 detects a waveform X as shown in FIG. 4a, and the vibration detector 3
When a waveform Y as shown in Fig. 4(b) is detected,
The product waveform X-Y becomes a trap as shown in Figure 4 (c), and from the positive and negative states of the waveform X-Y in Figure 4 (C), it can be seen that the initial motion of the P wave appeared at time t1. , time t2
It can be seen that the initial movement of the S wave appeared.

5 and 6 show an earthquake initial motion detection device as a second embodiment of the present invention, FIG. 5 is an explanatory diagram schematically showing its arrangement state, and FIGS. (b) is a vector diagram for explaining the action, and in FIGS. 5 and 6, the same reference numerals as in FIGS. 1 to 4 indicate substantially the same parts.

In the device of this second embodiment, a pair of vibration detectors 2.3 are arranged such that the angle α between their respective central axes 9.10 is an acute angle.

In general, the amplitude of the P wave of earthquake motion is often smaller than that of the S wave, so as in the first actual case described above, the angle between the pair of vibration detectors 2 and 3 made by their respective central axes 9 and 100 is ( 45°+45°-) If the angle is 90°, the sensitivity may be the same and the S wave component may become too strong.

Therefore, if the angle α is made acute as in the device of the second embodiment, the sensitivity will be emphasized for P waves, as shown in FIG. 6, or in other words, the sensitivity will be blunted for S waves. The problem as in the first actual case described above is eliminated, and the initial detection of P waves and S waves can be performed with high accuracy.

In each of the above-mentioned embodiments, a pair of vibration detectors 2.3 are shown arranged symmetrically with respect to the vertical axis 1 in the same plan view including the vertical axis 1. In addition to the vibration detectors 2 and 3, a pair of vibration detectors may be arranged in the same plane orthogonal to the plane containing the vertical axis 1 and tilted symmetrically with respect to the vertical axis. When two pairs of vibration detectors are provided like this, the accuracy of detecting the initial motion of an earthquake is further improved.

In addition, as in each of the above-mentioned embodiments, the correction coils 11 and 12
Instead of performing center position correction using the vibration detector 2
, 3, DC current may be supplied to the moving coils 7, 8 themselves, and in this case, between the current supply point to the moving coil 7.8 and the output ends 2a, 3a. A capacitor is interposed in the multiplication circuit 5 to prevent the direct current from flowing into the multiplication circuit 5.

In addition, there are the following means for correcting the operating center position of the vibration detector.

(1) Add an auxiliary spring to the vibration detector or readjust it.

(2) A diaphragm spring having non-linear load-deflection characteristics is combined and adjusted so that the vibration detector can maintain its center position in an inclined position.

Furthermore, as the vibration detectors 2 and 3, in addition to using moving coil type vibration detectors, piezoelectric type or electric φ type vibration detectors can also be used.

As described in detail above, according to the earthquake initial motion detection device of the present invention, each detection value of a pair of vibration detectors is multiplied by a multiplication circuit, and the positive or negative of the product as an output value is determined by an appropriate means. This has the advantage that the initial motion of an earthquake can be detected easily and accurately.

In addition, if the vibration detector is installed at an angle, a component of gravity acts on the vibration detector for horizontal motion, causing the operating part of the vibration detector to shift downward from the center of motion, and for vertical motion, the gravitational component will act. However, in the earthquake initial motion detection device of the present invention, the inclination of the vibration detector causes the operating part to move upward, making it unusable. can be adjusted and corrected, so the above-mentioned problems are not caused, and this has the advantage of contributing to highly accurate initial motion detection of an earthquake.

[Brief explanation of the drawing]

1 to 4 show an earthquake initial motion detection device as a first embodiment of the present invention, FIG. 1 is an explanatory diagram schematically showing its arrangement state, and FIG. The electric circuit diagram showing the device, Figures 3a and 3d are vector diagrams to explain their actions, Figures 4a to 4c are waveform diagrams to explain their actions, and Figure 5, Figure 6 shows the second embodiment of the present invention.
This shows an earthquake initial motion detection device as an example, and the fifth
The figure is an explanatory diagram schematically showing the arrangement state, Fig. 6 a-
d is a vector diagram for explaining the effect. 1... Vertical axis, 2.3... Vibration detector, 2as3a... Output end of vibration detectors 2 and 3,
4... Inclined base, 5... Multiplication circuit, 6
...Positive/negative discrimination means, 7, 8... Moving coil, 9, 10... Central axis line, 11, 12...
...DC type correction coil as correction means, 13,1
4... Support spring, 15.16... DC power supply, 17, 18... Magnetic field generating member.

Claims (1)

[Claims] 1. A device comprising a pair of vibration detectors disposed in the same plane including a vertical axis and symmetrically inclined with respect to the same vertical axis, and multiplying the detected values of these vibration detectors by each other. A multiplication circuit connected to each output terminal of the vibration detector to match the vibration detector, and means for determining whether the product of the detected values obtained by the multiplication circuit is positive or negative are provided, and Initial motion detection of an earthquake, characterized in that a correction means is provided for moving the vibration detector along its center axis in order to adjust and correct the operating center position of the vibration detector that has moved due to inclination. Device. 2. The initial motion detection device for an earthquake as set forth in claim 1, wherein the pair of vibration detectors are arranged with their central axes making an acute angle to each other.