JPH06313797A - Detecting device of earthquake - Google Patents

Abstract

PURPOSE:To simply execute detection of an earthquake. CONSTITUTION:A vibration sensor is provided in a gas meter for measuring the flow rate of a city gas and an output of the vibration sensor is given to a level discriminating means through a low-pass filter 42 filtering a frequency component of about 10Hz or below, so as to discriminate a seismic wave. When the occurrence of an earthquake is discriminated thereby, supply of the city gas is shut off by closing a shut-off valve provided in the gas meter, while the output of the vibration sensor is stored in a seismic wave memory. The state of the earthquake can be known by reading out the content of storage of the seismic wave memory, and also detection of the seismic center or the like can be executed easily, since this gas meter is provided at a large number of places.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus for detecting earthquakes.

[0002]

2. Description of the Related Art Conventionally, in order to detect the epicenter of an earthquake when it occurs, seismographs for detecting the earthquake have been arranged at a plurality of places and observed by these seismometers when the earthquake occurred. The epicenter is detected based on the seismic waveform.

[0003]

In such a prior art, a plurality of seismographs must be installed for constant observation, resulting in excessive installation place, equipment cost and labor.

An object of the present invention is to detect an earthquake easily,
It is to provide an earthquake detection device that can grasp the earthquake situation and further investigate the epicenter.

[0005]

DISCLOSURE OF THE INVENTION The present invention is directed to a vibration sensor for detecting vibration, an earthquake wave identification means for responding to the output of the vibration sensor and for identifying only an earthquake wave, and an earthquake response for the output of the seismic wave identification means. An earthquake detecting device comprising: an operating means for causing a moving body to perform a predetermined operation when an occurrence occurs, and an earthquake wave memory for storing an output of a vibration sensor in response to an output of the earthquake wave identifying means.

Further, according to the present invention, the seismic wave identifying means is about 10
A low-pass filter for filtering frequency components below Hz,
Means for discriminating the level of the output of the low-pass filter.

[0007]

According to the present invention, the vibration sensor detects the vibration, and the seismic wave identification means identifies only the seismic wave in response to the output of the vibration sensor. When the seismic wave is identified, the output of the vibration sensor indicates the seismic wave. Stored in memory. Therefore, by reading the seismic wave stored in the seismic wave memory, the situation of the earthquake can be grasped, and by providing such an earthquake detecting device at plural places,
It is also possible to detect the epicenter.

The earthquake detecting apparatus of the present invention is provided with an operating means for responding to the output of the seismic wave discriminating means and causing the operated body to perform a predetermined operation when the earthquake occurs, for example, by supplying city gas when the earthquake occurs. A gas meter that measures the flow rate may have a configuration in which the supply of gas is shut off.Since such a gas meter is provided in each household, by installing the earthquake detection device for each gas meter, an extremely large number can be installed. It will be possible to observe seismic waves at these locations.

According to the present invention, to identify seismic waves,
The output of the vibration sensor is applied to a low-pass filter that filters frequency components of about 10 Hz or less, and the output of the low-pass filter is level-discriminated, so that a malfunction does not occur due to, for example, a shock wave when an obstacle collides with a gas meter. . The seismic wave identifying means may have other configurations, for example, the seismic wave may be identified by comparing the output of the vibration sensor with the seismic wave stored in the memory in advance corresponding to the seismic wave. , And other configurations may be used.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a perspective view of a seismoscope 10 used in the earthquake detecting apparatus of the present invention. This shock absorber 10
A block body 11 that is a rectangular parallelepiped or a cube and three mounting surfaces 12, 13, 1 of the block body 11 that are orthogonal to each other
Seismic sensors S1, S2, S3 fixed to 4 respectively
Have and. The block body 11 may be made of metal such as iron or aluminum, or may be made of synthetic resin, and is rigid. The sensors S1, S2, S3 have the same configuration and may be indicated generally by the reference sign S.

FIG. 2A is a sectional view of the sensor S1.
FIG. 2 (2) is a perspective view showing the sensor S1 by cutting out.
The sensor S1 includes a pendulum 15 supported in a cantilever manner, and a pair of electrodes 16 arranged on both sides (upper and lower sides in FIG. 2) of the pendulum 15 in a direction in which the pendulum 15 reciprocally vibrates (vertical direction in FIG. 2). , 17 and. The pendulum 15 includes a pendulum body 18 and a cantilever support portion 19, and the cantilever support portion 19 is continuous with the attachment portion 20. The pendulum 15 and the mounting portion 20 are made of conductive single crystal silicon. A spacer 21 is arranged so as to face the pendulum body 18. The electrodes 16 and 17 are formed on flat glass plates 22 and 23, and these electrodes 16 and 17 are thin films made of aluminum and are formed by a method such as vapor deposition. The glass plates 22 and 23 are fixed to substrates 24 and 25 made of conductive single crystal silicon, respectively.
6 and 17 are connection holes 2 formed in the glass plates 23 and 22.
It is electrically connected to the substrates 24 and 25 via 6 and 27. Thus, the sensor S1 is constructed symmetrically with respect to the plane of symmetry 28 of FIG. The cantilevered support portion 19 is fully elastic and therefore free of hysteresis, brittleness and creep. Mounting part 20 and glass plates 22 and 23
The substrates 24 and 25 are completely fused via the silicon dioxide, and the spacer 21 is also the same, and thus the internal space 29 is hermetically sealed and is in a vacuum state. The distances d1 and d2 between the pendulum body 18 and the electrodes 16 and 17 are 2 in a natural state, that is, in a state where no acceleration is applied.
˜5 μm, and d1 = d2 in this embodiment. The spacer 21 is made of the same material as the pendulum 15 and the mounting portion 20. In this way, the sensor S1 is, for example, 4 mm long, 4.5 mm wide, and 3 mm thick, and has a minute shape. X in the thickness direction of the pendulum 15 (the vertical direction in FIG. 2)
In the case of the direction, the sensor S1 is fixed to the mounting surface 12 of the block body 11 of FIG. The remaining sensors S2, S3 are similarly constructed.

Such a sensor S1 has stable characteristics over a long period of time and can detect acceleration with high accuracy in a wide temperature range of -40 to + 125 ° C. Since the sensor S1 is symmetric with respect to the surface 28 and therefore expands uniformly even by thermal expansion, the combined value of the capacitances of the pendulum body 18 and the electrodes 16 and 17 does not change. Further, the sensor S1 is provided with the sandwich-shaped electrodes 16, 1 to prevent an over-impact of about 4000 g (g is a gravitational acceleration), that is, a shake of the pendulum body 18 due to the excessive acceleration.
7. Therefore, since the glass plates 22 and 23 limit the pendulum body 18, the cantilever support portion 19 supporting the pendulum body 18 is not subjected to an excessive bending force, and therefore the cantilever support portion 19 is supported.
Can be prevented from being damaged. Furthermore, according to this structure, the selectivity in the sensitivity direction is excellent. That is, since the sensor S1 including the pendulum 15 forms a laminated structure in the vertical direction of FIG. 2, the sensitivity is excellent in the vertical direction of FIG. 2, and the sensitivity in the vertical direction to the paper surface of FIG. Extremely low.

Further, according to this structure, the pendulum 15
Also, the mounting portion 20 can be finely processed easily by the semiconductor etching technique, and the quality of the mounting portion 20 can be stabilized and a low price due to mass production can be realized by drastically reducing the number of manufacturing steps by automating the sensor S1. Further, the sensor S1 can be manufactured by the silicon wafer technology, and since the temperature coefficient is very small, the sensor S1 can be adjusted and shipped at room temperature, which also can significantly reduce the number of manufacturing steps. Further, it is possible to adopt a micro-etching technique, which enables miniaturization. Remaining sensor S
2 and S3 also have the same structure as the sensor S1.

FIG. 3 is a block diagram showing the electrical construction of an embodiment of the present invention. Three sensors S1, S2, S3
The pendulum 15 and the electrodes 16 and 17 of the
And lines 31; 32, 33 through the substrates 24, 25
Respectively connected to. Pendulum 15 and each electrode 16, 17
When the capacitance between and is C1 and C2, C1 = C2 in the natural state where no acceleration exists, and when acceleration occurs, the intervals d1 and d2 (see FIG. 2 (1) described above) are generated by the law of inertia. ) Are different from each other, which results in C1 <C
2 or C1> C2. The conversion circuit 34 uses the line 3
1, 32, 33 connected to the lines 35, 36 by the voltages V1, V corresponding to the capacitances C1, C2 of one sensor S1.
2 is output respectively.

[0015]

[Equation 1]

Here, V0 is a voltage that the temperature compensating circuit 37 gives to the converting circuit 34 through the line 38, and performs offset adjustment together with the circuit 39. Differential amplifier circuit 4
0 responds to the outputs on lines 35 and 36, respectively, and derives on line 41 an output V3 which is the difference between the voltages V1 and V2.

[0017]

[Equation 2]

Here, the combined value (C1-C2) / (C1 + C
2) is proportional to the acceleration of the sensor S1 in the x direction.

Although the above description was made primarily with respect to sensor S1, the pendulum 15 of sensor S1 is
Commonly connected to the line 31 with the pendulum of the residual sensors S2, S3, and each electrode 16, 17 is connected with the corresponding electrode of the residual sensor S2, S3 in a line 32, 3
3 is connected. Therefore, C1 and C2 shown in the above equations 1 to 3 can be considered as parallel capacitances of these sensors S1, S2 and S3.

The signal derived from the amplifier circuit 40 on the line 41 is applied to the low-pass filter 42.

FIG. 4 is an electric circuit diagram showing a specific structure of the low-pass filter 42. This low pass filter 4
2 has a characteristic of selectively extracting a signal having a center frequency component of 2 to 5 Hz, which is a seismic wave, and blocking a shock wave of, for example, about 10 Hz, that is, selecting only the seismic wave shown in FIG. The cut-off frequency f0 is determined so that the shock wave is cut off. The low-pass filter 42 includes an operational amplifier 43, a resistor R1, and a resistor R1.
2 and the capacitor C10, and the cutoff frequency f0 is as shown in Expression 4. For example, f0 = 10 Hz.

[0022]

[Equation 3]

FIG. 6 is a diagram showing the characteristics of the low-pass filter 42. Ideally, as shown in FIG. 6, the low-pass filter 42 functions to pass a signal in the frequency band below the cutoff frequency f0 and to cut off the signal in the frequency band above the cutoff frequency f0. Referring again to FIG. 3,
The output of the low-pass filter 42 is given to the comparison circuit 44 to perform level discrimination.

FIG. 7 is a waveform diagram for explaining the electrical operation of the embodiment shown in FIG. Sensors S1 to S3
When an earthquake is detected by, the seismic wave shown in FIG. 7 (1) is derived from the amplifier circuit 40 to the line 41, and the output of the low-pass filter 42 becomes as shown in FIG. 7 (2). The comparison circuit 44 level-discriminates the output of the low-pass filter 42 at the discrimination level 45 having an acceleration of 200 gal.
The control signal shown in (4) is given, and the seismic wave is detected by this.

On the other hand, as shown in FIG. 8 (1), when a shock wave other than the seismic wave is detected by the sensors S1 to S3 and the signal of the detected shock wave is derived from the amplifier circuit 40 to the line 41. The output of the low-pass filter 42 is as shown in FIG. 8 (2), which is low level. The output of the shock wave through the low-pass filter 42 is less than the discrimination level 45 as shown in FIG. 8 (3). Therefore, the output of the comparison circuit 44 remains low level as shown in FIG. Therefore, no shock wave is detected. In this way, only seismic waves can be selectively detected.

FIG. 9 is a graph showing the experimental results of the present inventor. The sensor S1 measures the output voltage at a vibration frequency of 10 Hz by a vibrator in a direction in which the symmetry plane 28 is horizontal and is perpendicular to the symmetry plane 28, and the magnitude of the vibration at this time is 0.2 g peak and is constant. Then, the characteristic line 47 was obtained. Further, the sensor S1 is connected to the symmetry plane 28
The characteristic line when the vibration is applied to the symmetry plane 28 in the vertical direction in the same manner as described above is shown by 48. Even if the mounting posture of the sensor S1 is changed in this way, the discrimination level of the signal derived from the amplifier circuit 40 corresponding to the sensor S1 to the line 41 is substantially the same, and thus the detected acceleration is
It was confirmed that the sensor S1 hardly depends on the mounting posture. This facilitates mounting of the sensor S1.

FIG. 10 is a perspective view showing a cutaway portion of a gas meter 50 equipped with the seismic sensor 10, and FIG. 11 is a system diagram showing a simplified gas flow of the gas meter 50. Referring to these drawings, a gas is supplied from an inlet 51 of a gas meter 50, a gas is supplied from a shutoff valve 52 to a gas meter main body 53 such as a membrane gas meter through a passage 52, and the gas measured here is discharged. It is supplied to the gas consuming equipment from 54. A wiring board 55 is mounted on the gas meter 50, a lithium battery 56 that can be used for a long period of time is provided on the wiring board 55, and the electric circuit shown in FIG. 3 is mounted. The vibration sensor 10 is mounted on the wiring board 55, and the remaining electric circuit shown in FIG. 3 is also mounted on the wiring board 55. When an earthquake is detected by the control output circuit 46, an indicator lamp 57 provided on the wiring board 55
Lights up and it is detected that an earthquake has occurred. The control output circuit 46 also operates to shut off the shutoff valve 52 when an earthquake is detected.
Shut off. This prevents the gas from being supplied to the gas meter main body 53 and the gas outlet 54, and thus prevents the fuel gas from being supplied to the gas consuming device on the downstream side of the gas meter 50 and leaking the fuel gas. Safety is secured.

The amount of gas detected in the gas meter main body 53 is detected by the flow rate sensor 57 and is detected by the wiring board 5
Processing circuit 5 such as a microcomputer mounted on 5.
8 and the measured value is derived as an electric signal. Further, an external signal 59 from a city gas alarm device which is provided outside for detecting leakage of city gas or an incomplete combustion alarm device which detects that incomplete combustion has occurred and the carbon monoxide concentration has increased is It is provided to the processing circuit 58 via the wiring board 55, and thereby the shutoff valve 52 is closed. The battery 56 supplies electric power to the electric circuit mounted on the wiring board 55.

Referring again to FIG. 3, the signal derived from amplifier circuit 40 on line 41 is temporarily stored in memory 93. The low-pass filter 42 and the comparison circuit 44 constitute seismic wave identification means. The memory 93 temporarily stores the waveform of the seismic wave from the amplifier circuit 40 and other vibration values. When the seismic wave is identified by the combination with the low pass filter 42 and the comparison circuit 44, the control output circuit 46 operates the memory 93 and the seismic wave memory 94, and the memory 93 when the seismic wave is generated.
Seismic waves of the seismic wave memory 94 store area 94a, 94
b, ..., 94i.

FIG. 12 is a flow chart for explaining the operation of the electric circuit shown in FIG. Step n1
~ Moving to step n2, the sensor S constituting the seismic sensor 10
When vibration is detected in steps S3 to S3, the vibration waveform is stored in the memory 93 in step n3. When the seismic wave identification means realized by the combination of the low-pass filter 42 and the comparison circuit 44 determines that the seismic wave is the seismic wave in step n4, the control output circuit 46 closes the shutoff valve 52 as described above. The display lamp 57 is turned on, and in step n5, the seismic wave stored in the memory 93 is transferred to and stored in the seismic wave memory 94. The seismic wave memory 94 includes the storage areas 94a to 94i as described above, and thus can store seismic waves a plurality of times.

By reading the seismic wave stored in the seismic wave memory 94 in this manner, the condition of the earthquake can be grasped and the epicenter can be detected. According to such a configuration, it is possible to grasp the situation of the earthquake and to detect the epicenter without using a seismograph installed in a specific place, and the configuration is It is simple and the gas meter 50 is provided for each home, so that it is possible to observe seismic waves at a very large number of places, and it is possible to grasp the earthquake more accurately.

FIG. 13 is a sectional view of a seismic sensor 70 according to another embodiment of the present invention. The seismic sensor 70 can be used in place of the sensors S1 to S3 described above.

The seismic sensor 70 has a conductive spherical pendulum 72 supported by a support portion 71, and a plurality of pairs of electrodes 73 surrounding the pendulum spaced apart from the pendulum 72. The center of the pendulum 72 is reference numeral 7.
In a natural state, that is, in a state where acceleration is not applied, the center of the virtual spherical surface on which the electrode 73 is formed coincides with the center 74. This virtual spherical surface is formed by a glass spherical shell 75, and the spherical shell 7
The electrode 73 is formed on the inner peripheral surface of the electrode 5 by vapor deposition or the like. The electrode 73 is, for example, an aluminum thin film. The pendulum 72, the supporting portion 71 supporting the pendulum 72, and the substrate 76 connected to the supporting portion 71 are made of conductive single crystal silicon.

FIG. 14 (1) is a simplified perspective view showing the inner peripheral surface of the spherical shell 75, and FIG. 14 (2) is a developed view of the inner peripheral surface of the spherical shell 75. Referring to these drawings, the electrodes 73 are formed point-symmetrically with respect to a center 74, and a plurality of pairs (three in this embodiment) of electrodes 73a, 73b; 7 are formed.
3c, 73d; 73e, 73f are formed. 75 spherical shells
The supports 77 and 78 for supporting the conductive material may be formed of conductive single crystal silicon or the like. The support portion 71 is fully elastic and therefore free of hysteresis, brittleness and creep. The spherical shell 75 and the supports 77, 78 can be completely fused, for example via silicon dioxide,
The internal space 79 is airtight and is in a vacuum. The distance between the pendulum 74 and the electrode 73 is about 2 to 5 μm in a natural state, that is, in a state where no acceleration is applied. Such a sensor 70 has, for example, a length of 4 × width of 4.5 × thickness of 3 mm, and is formed in a minute shape.

Such a sensor 70 has stable characteristics over a long period of time and can detect acceleration with high accuracy in a wide temperature range of -40 to + 125 ° C. The sensor 70 is point-symmetric with respect to the point 74, and therefore the whole expands uniformly by thermal expansion, so that the combined value of the capacitances of the pendulum 72 and the electrode 73 does not change. Further, the sensor 70 is provided with a pendulum 72 due to an over-impact of about 4000 g (g is a gravitational acceleration), that is, an over-acceleration.
Since the deflection of the beam is restricted by the electrode 73, and thus the spherical shell 75, the supporting portion 71 supporting the pendulum 72 is not subjected to an excessive bending force, and therefore the supporting portion 71 is prevented from being damaged.

Further, in the sensor 70, the pendulum 72 and the supporting portion 71 can be manufactured by fine processing in the semiconductor etching technique. The automation of the sensor 70 of the present invention greatly reduces the manufacturing man-hours to stabilize the quality,
It is possible to realize a low price due to the effect of mass production. Also, the sensor 70 can be manufactured by the silicon wafer technology,
Moreover, since the temperature coefficient is very small, the temperature can be adjusted and shipped at room temperature, which can also significantly reduce the number of manufacturing steps. Further, since micro etching technology can be adopted, miniaturization is possible. Electrodes 73a-73f are generally indicated by reference numeral 73 as described above. Electrode 73 and spherical shell 75, and further supports 77, 7
8 may be divided into a plurality of pieces, for example, a half-divided shape to facilitate the assembly.

FIG. 15 is a block diagram showing an electrical configuration related to the seismic sensor 70. The pendulum 72 is connected to the line 31, and each pair of electrodes 73a to 73 is formed.
Corresponding electrodes 73b, 73d, 73f of f are commonly connected to line 32, and corresponding electrodes 73a, 7d
3c and 73e are commonly connected to the line 33. The capacitance between the pendulum 72 and the electrodes 73a and 73b is C1 and C2.
Then, in a natural state where no acceleration exists, C1 =
When the acceleration is C2, the distances d1 and d2 (see FIG. 2 (1) described above) are different from each other due to the law of inertia, which results in C1 <C2 or C1> C2. The conversion circuit 34 is connected to the lines 31, 32 and 33, and the capacitance C of one sensor 70 is connected to the lines 35 and 36.
The voltages V1 and V2 corresponding to 1 and C2 are output, respectively. Other configurations of the above-described embodiment described with reference to FIGS. 13 to 15 are as in the above-described embodiment.

According to the seismic sensor 70 shown in FIGS. 13 to 15, the conductive spherical pendulum is supported by the supporting portion, and the pendulum on the virtual spherical surface has the same center as the center of the pendulum in the natural state. Forming multiple pairs of electrodes on the
Since each pair of electrodes is formed point-symmetrically from the center of the phantom spherical surface, it is possible to detect acceleration due to vibration such as an earthquake in any three-dimensional direction, without restricting the mounting posture of the seismic sensor. You can

This seismic sensor has a plurality of pairs of point-symmetrical electrodes on a virtual spherical surface having the same center as the center of the pendulum in its natural state. Since the capacity is detected and the capacity detection output is level discriminated, it is possible to sufficiently downsize the structure as compared with the prior art described with reference to FIG. It is possible to prevent variations in the characteristics of the sensor for each product and further improve the sensitivity.

Further, according to the present invention, the pendulum of the seismic sensor is made of conductive single crystal silicon together with the supporting portion, and electrodes are formed along an imaginary spherical surface. The electrodes are, for example, glass spherical shells. It can be formed on the inner surface and thus the production can be achieved, for example using semiconductor etching techniques, which is easy to automate and enables mass production. Further, according to the present invention, the vibration displacement of the pendulum is limited by the electrodes, so that it is possible to prevent an excessive bending force from acting on the supporting portion, and to prevent damage.
Thus, even if a large acceleration acts on the seismic sensor, the seismic sensor is not destroyed.

Furthermore, according to the present invention, a plurality of pairs of corresponding electrodes are commonly connected, and therefore, it is possible to detect vibration acceleration in all three-dimensional directions.

Although the present invention has been implemented in connection with a gas meter, the present invention may be implemented in a wide range of other operating means such as shutoff valve 52 and the like.

[0043]

As described above, according to the present invention, the vibration is detected by the vibration sensor, and only the seismic wave is discriminated by the seismic wave discriminating means in response to the output of the vibration sensor. The operation means is operated by cutting off the supply of city gas, and the output of the vibration sensor is stored in the seismic wave memory when an earthquake occurrence is detected by the seismic wave identification means. With this, it is possible to observe earthquakes at a large number of places, and therefore it is possible to reduce the installation site and equipment costs as well as the labor for earthquake observations.

According to the invention, the seismic wave identifying means is
Since a low-pass filter for filtering frequency components of about 10 Hz or less is provided and the output of the low-pass filter is level-discriminated, the seismic wave can be identified with a simple configuration.

[Brief description of drawings]

FIG. 1 is a perspective view showing a sensor 10 according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a sensor S1.

FIG. 3 is a block diagram showing an electrical configuration of a seismoscope associated with the sensors S1, S2, S3.

FIG. 4 is an electric circuit diagram of a filter 42.

FIG. 5 is a waveform diagram showing an earthquake wave and a shock wave.

FIG. 6 is a graph showing characteristics of the low pass filter 42.

FIG. 7 is a diagram for explaining the operation of one embodiment of the present invention when a seismic wave is generated.

FIG. 8 is a waveform diagram for explaining the operation of the seismoscope according to the embodiment of the present invention when a shock wave is generated.

FIG. 9 is a graph showing an experimental result by the present inventor of the sensor S1.

FIG. 10 is a seismoscope 1 according to one embodiment of the present invention, which includes a block body 10 to which the above-described sensors S1, S2 and S3 are attached.
It is a perspective view which notches and shows a part of gas meter 50 which mounted 0.

11 is a simplified diagram showing the flow of gas fuel in the gas meter shown in FIG.

FIG. 12 is a flowchart for explaining the operation of the electric circuit shown in FIG.

FIG. 13 is a sectional view of a seismic sensor 70 according to another embodiment of the present invention.

14 is a diagram showing electrodes 73a to 73f of the seismic sensor 70. FIG.

FIG. 15 is a block diagram showing an electrical configuration of a seismic sensor associated with the seismic sensor 70.

[Explanation of symbols]

 10 seismic sensor 11 block body 12, 13, 14 mounting surface 15 pendulum 16, 17 electrode 18 pendulum body 19 cantilever support part 22, 23 glass plate 34 conversion circuit 40 amplification circuit 42 low-pass filter 44 comparison circuit 46 control output circuit 50 Gas meter 52 Shut-off valve S1, S2, S3 sensor 70 Seismic sensor 71 Support part 72 Pendulum 73, 73a to 73f Electrode 74 Center 75 Ball shell 76 Substrate 77, 78 Support 93 Memory 94 Seismic wave memory

Claims (2)

[Claims] 1. A vibration sensor for detecting vibration, a seismic wave identification means for responding to the output of the vibration sensor and for identifying only seismic waves, and a response to the output of the seismic wave identification means for preliminarily applying to an object to be operated when an earthquake occurs. An earthquake detecting device comprising: an operation means for performing a predetermined operation; and an earthquake wave memory for storing an output of a vibration sensor in response to an output of the seismic wave identifying means. 2. The earthquake detecting device according to claim 1, wherein the seismic wave identifying means includes a low-pass filter for filtering frequency components of about 10 Hz or less, and a means for discriminating a level of the output of the low-pass filter.