JPH11132840A - Optical pendulum seismic sensor as well as protection-against-disasters alarm device and protection-against-disasters alarm judgment method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical pendulum seismic sensor as a protection-against- disasters alarm device and a protection-against-disasters alarm judgment method, using the sensor, in which a pendulum motion containing a miscelleneous tremor, large-scale seismic waves and small-scale faint seismic waves are discriminated and detected without being subjected to the influence of a noise, in which a malfunction is small, whose performance is stable, whose sensitivity is high and which are low-cost. SOLUTION: An optical-miscelleneous-tremor removal means by which only seismic waves are extracted from miscelleneous vibrations detected by a sensor is built in a seismic sensor which optically detects a pendulum motion. The optical-miscelleneous-tremor removal means is composed of the intensity distribution of light, a magnitude relationship and a geometrical arrangement which are formed by the arrangement constitution of an optical component such as a perforated plate 4 or the like which gives a light intensity distribution to light from a light source 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pendulum type sensor for detecting ground motion displaced by an earthquake, and more particularly to optically detecting the motion of a pendulum to reduce the influence of noise and to stabilize the motion. TECHNICAL FIELD The present invention relates to an optical pendulum earthquake sensor capable of obtaining improved performance, a disaster prevention alarm device using the sensor, and a disaster prevention alarm determination method.

[0002]

2. Description of the Related Art Many seismometers known in the art are:
This is a sensor to which the principle of the pendulum is applied and the movement of the pendulum is electrically detected using a coil or the like.
By appropriately selecting the natural period of these pendulums and the signal processing method, seismometers of a speed method, an acceleration method, a displacement method, and the like have been manufactured. These seismometers were of high academic precision for most academic uses.

[0003]

In such a pendulum type seismometer which is widely used, the purpose is to catch a sensitive earthquake, and a long distance such as insensitive at an observation point is used. It was not a structure that could effectively detect large-scale earthquakes that occurred in (for example, tsunami earthquakes of M = 7.0 or more that occurred 1000 km or more from the observation point). Also, as mentioned above, the conventional pendulum seismometer
Most of them are suitable for academic use, and high accuracy and reproducibility are required for the sensors themselves, which makes them extremely expensive.
Strict ones are required for inclination and vibration environment. Therefore, it has been difficult to provide such sensors for academic use for general purposes. If an electric circuit type filter is inserted in the sensor for general use, the important seismic motion may not be detected, and if a threshold is set poorly, it may be possible to detect noise and temperature fluctuations. there were. Further, when trying to measure a weak vibration with a conventionally used electric pendulum sensor, the signal becomes weak, and noise may be mixed in from an amplifier or a signal line, making measurement impossible.

[0004] In order to overcome these problems, it is considered preferable to detect the motion by an optical system using optical components or elements. In an optical sensor, the vibration is expressed by the movement of the optical axis, and the vibration is expressed by a small amount. Even with vibration, if the intensity of the light source is high, the signal intensity increases, and there is no possibility of being buried in noise.

However, the cost of the conventional optical sensor tends to increase due to temperature compensation (measures against temperature) and assembly accuracy. However, this is
It is only required for sensors intended for quantitative measurement of seismic waves.Sensors intended for simply detecting seismic waves also include design conditions that do not need to be considered so much. If the physical characteristics can be sufficiently utilized, it is considered that the cost of the earthquake sensor can be reduced.

[0006] Then, when the physical characteristics of the seismic wave were investigated, it was found that the following can be generally said. (1) Long-distance seismic waves include many long-period (1 second or longer) waves, and conversely, short-distance seismic waves include many short-period waves. (2) The greater the magnitude of the earthquake, the greater the crustal deformation, and the greater the displacement at the observation point, even if it is insensitive. Conversely, for an earthquake with a small magnitude, the displacement is small even if the event is a sensitive earthquake at the observation point. (3) Seismic waves are different from urban vibrations such as construction and railways.
By evaluating the amount of displacement of the pendulum per unit time when the rise of the P wave or the S wave is rapid, it is possible to distinguish between the seismic wave and the urban vibration. In addition, since the P wave and the S wave are clearly separated from each other, discrimination is further facilitated by detecting the P wave and the S wave. (4) The magnitude of destruction due to seismic waves can be expressed by vector quantities such as acceleration, velocity, and displacement, and by evaluating those vector quantities, it is almost possible to evaluate the damage scale.

[0007] Among the above matters, a study was made with particular attention to (2) and (4). As a result, it was found that the use of an optical sensor could solve the problem at low cost. In particular, a simple earthquake sensor only needs to be able to accurately detect only the fact that there was an earthquake that is likely to cause damage, and if vibrations other than earthquakes can be effectively eliminated, the optical type is the best choice. is there.

[0008] In the case of the optical system, as described above, there is a concern about disturbance due to a temperature change. However, since the temperature change is not as sharp as the change due to the seismic motion, the discrimination is very easy. In addition, usually, such as vibration due to construction vibration or railway,
A detailed study on the elimination of vibrations called microtremors revealed that there were certain patterns in the occurrence time zone and amplitude. In particular, since these vibrations do not exceed a certain level in amplitude, it has been found that microtremors can be easily removed by appropriately selecting and combining the area and aperture of the optical element, the aperture, the optical spatial filter, and the like. .

As described above, according to the present invention, in a pendulum type sensor, the pendulum motion is optically detected, and the size relationship between figures incorporated in the optical system and the geometrical arrangement of the light source are combined. From pendulum motion including small tremors to large-scale and small-scale weak seismic waves can be detected and detected without being affected by noise, eliminating small tremors and having few malfunctions. To provide a low-cost optical pendulum seismic sensor that is easily responsive to an earthquake with large fluctuations, has stable performance, is sensitive to the inclination of the ground, and has a disaster prevention alarm device and a disaster prevention alarm determination method using the sensor. With the goal.

[0010]

Therefore, an optical pendulum seismic sensor according to the present invention is constructed as follows. The sensor has a pendulum-type seismic-motion detecting means and an optical noise and microtremor removing means. The pendulum-type seismic-motion detecting means is supported by a bearing stand 9 when a simple pendulum is used as shown in FIG. A pendulum, which is suspended from the fulcrum 2 by a supporting cylinder 8 and at least two suspension lines 6 at the fulcrum 2 and is constituted by a weight 3 which can be swung by vibration, and irradiates light to the pendulum structure The light source 1 includes an optical fiber 7 that guides light from the light source 1 and an optical sensor 5 that is a photoelectric conversion unit that converts light emitted from the optical fiber 7 into an electric signal. The optical noise and tremor removing means includes a perforated hole having an end face of the optical fiber 7 and an opening smaller than the optical sensor 5 for adjusting the light emitted from the optical fiber 7 to an appropriate intensity and entering the optical sensor 5. An optical component comprising the plate 4 is provided. With these arrangements, noise vibration (noise) is removed and only the seismic motion is extracted as a detection signal of the optical sensor 5.

The operation of the optical pendulum earthquake sensor will be described. In particular, here, FIG. 2 shows an equivalent functional configuration of the optical micro-movement removing means which is a feature of the present invention, and FIGS. 3 and 4 show the basic operation of the configuration. The optical noise and vibration removing means is an optical emission means 12 (an opening A in FIGS. 2 to 4) for emitting light from the light source 1 using the end face of the optical fiber 7.
Is provided upstream of the photodiode 14 which is the optical sensor 5 in the light propagation direction.
And an optical incidence means 13 using the same. And
The light from the light source 1 is applied to the pendulum-type seismic-motion detecting means, and emitted from the optical emission means 12 incorporated therein. The emitted light is applied to the photodiode 14 through the optical incidence means 13 as an irradiation light flux 15. Irradiated. The optical incident means 13 has a function of effectively preventing the influence of scattered light and other stray light generated from the irradiation light beam 15 and extracting and detecting seismic motion from vibrations including microtremors by an operation described later. .

Although the optical emission means 12 and the optical incidence means 13 are shown as simple perforated plates in the drawing, they are equivalent to express the effects produced by optical components, optical elements, image masks and the like. If the light (light vector) transmitted through this portion can be given a spatial light intensity distribution in the horizontal direction and can remove noise and tremor, for example, the structure of the embodiment described later can be used. As described above, an image photographed on a photographic film or an optical fiber core wire having a different structure may be used. Since the same effect can be obtained by using any of these configurations, the details will be described in each embodiment, and only the basic operation will be described here.

As shown in FIG. 2, the parts corresponding to the pendulum are the suspension line 6 and the optical emitting means 12. When an earthquake motion or a microtremor is added to the motion, it moves in the direction of arrow a in FIG. In this case, the pendulum has a property of returning to the original point, and the optical emitting means 12 of the pendulum moves in the direction of arrow b. At this time, if the size of the opening of the optical incidence means 13 is made larger than the size of the opening of the optical emission means 12, the irradiation light beam
Falls within the fluctuation range, and the electric output of the photodiode 14 does not fluctuate. In this way, by providing a magnitude relationship between the optical emission means 12 and the optical incidence means 13, a certain fluctuation width can be eliminated. For example, if the amplitude is set to the amplitude of a micro-earthquake or miscellaneous tremor that is not desired to be detected, these can be removed.

FIG. 4 shows a case where a ground motion larger than the ground motion shown in FIG. 3 is detected. In this case, the swing width of the optical emission unit 12 is larger than that of the optical incidence unit 13. At this time, the electric output of the photodiode 14 fluctuates and shows an output waveform as shown in FIG. This is the large-scale earthquake detection characteristic of the optical pendulum earthquake sensor of the present invention. This detection characteristic is especially effective for earthquakes that are sensitive at the observation point. Using this characteristic, it is possible to detect the magnitude of the earthquake without malfunction even in a sensitive earthquake Becomes

In the following, a recent earthquake that has occurred will be considered based on records observed by the present inventors. FIG.
An earthquake record of M = 3.2 and a depth of 10 km (a distance from the observation site to the epicenter of 30 km by a sensitive seismograph) occurred in Nada Ward, Kobe City on March 14, and Fig. 13 shows the earthquake 1 shows an observation record of the earthquake sensor according to the present invention. Although the data of the earthquake is not clear, Fig. 14 shows the record of the earthquake that occurred on May 16 of the same year. FIG. 15 shows an observation record of the earthquake sensor according to the present invention for the earthquake. A close examination of all the seismic records shows that the waveforms are almost the same, and the hypocenter distances are almost the same, which is sufficient for comparison. Also,
Fig. 16 shows the M = that occurred at the epicenter, Toyohashi on May 24 of the same year.
5.6 shows an earthquake record at a depth of 30 km (distance from the observation site to the epicenter 194 km), and FIG. 17 shows an observation record of the earthquake by the earthquake sensor according to the present invention.

By comparing these observation data, the features of the present invention can be fully understood. The seismic acceleration in FIGS. 14 and 16 is 1 to 2 gal in the horizontal direction (X-Y direction),
In terms of acceleration, the earthquake in FIG. 14 and the earthquake in FIG. 16 are almost equivalent. However, comparing the observation records of the earthquake sensor according to the present invention shown in FIG.
Is larger than 20 cm on the recording paper, but almost only a trace is recognized in FIG. 13 or FIG. Also,
Also in FIG. 12, which is considered to be an earthquake having a magnitude M larger than that of FIG. 14 at the same epicenter as that of FIG. 14, the present invention only responds to traces. This is because the difference between the magnitudes M in FIGS. 14 and 12 is not so large. Both of the above earthquakes are sensible in the bodily sensation, and it was difficult to determine the magnitude of the earthquake by bodily sensation, such as the doors and shojis rattling, but with the earthquake sensor of the present invention, It is noted that the difference between the magnitudes M is clearly discriminated. Also, comparing the two earthquake records, it can be seen that the period of the earthquake of FIG. 16 is longer than that of the earthquakes of FIG. 12 and FIG.

Considering this, it is considered that the earthquake sensor of the present invention does not react to acceleration but reacts to velocity components and displacement components contained in seismic waves. The grounds are the earthquake records of FIGS. 12 and 14, and the observation records of the earthquake sensor according to the present invention of FIGS. 13 and 15. That is, despite the fact that the seismic acceleration in FIG. 12 exceeds the seismic acceleration in FIG. 14, the observation records in FIG. 13 and FIG.
Only approximately the same strength is observed. Considering that the seismic waveforms of both are almost the same, this consideration is considered correct, and as is generally known, the pendulum responds to the displacement of ground motion. Conceivable.

As described above, comparing the observation data with each other, it is considered that the frequency characteristics are deeply involved in the earthquake sensor of the present invention. Therefore, the vibration analysis of the sensor with this structure was performed, and how the period of the seismic motion contributed to the natural period of the sensor was examined.

References and examination results are shown below, and FIG. 37 shows a pendulum model of the present invention used in the examination. For the equation of motion of this pendulum model, refer to the following references: Tatsuo Usami: Earthquake Engineering for Architecture: Ichigaya Publishing Co. (1994, First Edition, 3rd ed.), P41-45, explanation of theoretical analysis, Etsuzo Shima: Easy-to-understand seismology: Kashima Press (1989)
Please refer to FIG. 3.4 of p70 for detailed results of vibration analysis. Here, a comparison with the present invention is shown only for the result derived from the diagram for explanation and the equation of motion.

When the pendulum as shown in FIG. 37 is excited by a seismic wave, it is clear from the above-mentioned observation results that the vibration of the pendulum varies depending on the period of the seismic wave. Further, it is considered that the detection characteristic shown in FIG. 20 described later is also deeply related to the vibration characteristic. When the pendulum in FIG. 37 is excited by the seismic wave, the mass m is displaced by dx, and the vibration is recorded on the virtual recording drum with the amplitude a. The amplitude a has a relationship as shown in the following equation (1).

(A / dx) = (L / l) = V (1) In FIG. 37, V is the geometric magnification, L is the length from the pendulum fulcrum to the virtual recording drum (corresponding to the light receiving surface), s is the trajectory drawn by the pendulum.

The period of this trajectory, that is, the period of the earthquake is T
When the natural period of the pendulum is set to T0, when T >> T0 (when the natural period of the pendulum is shorter than the period of the earthquake), the amplitude of the pendulum is proportional to 1 / T ＾ 2. It is a total. When T << T0 (when the natural period of the pendulum is longer than the period of the earthquake) The amplitude of the pendulum is an approximate value related to a and s, and the pendulum functions as a displacement gauge. When T = T0, the pendulum is in a resonance state and only detects an earthquake.

It is obvious that steady observation is required when trying to remove the fine tremor from the pendulum model in FIG. When the fine tremor component can be obtained from the daily observation, an opening having an amplitude corresponding to the fine tremor amplitude may be provided according to the equation (1). In practice, the opening may be slightly larger than that obtained, and in the Kinki region, the magnification may be determined within the range of 1 to 1.2. However, since this size is specific to each region, it is desirable to calibrate for each installation location.

The vibration explained based on the relation of the above equation (1) has been dealt with only one-dimensional vibration.
Actual seismic motion is accompanied by displacement of the crust, and its waves are accompanied by tilt and rotation angles. Fig. 3 shows the degree of freedom of this pendulum.
FIG. Although what was theoretically shown was the vibration in the xy plane in FIG. 37, actually, as shown in FIG. 38,
Simultaneously with the occurrence of the seismic motion, the rotation angle θ of the z-axis and the inclination angle φ accompanying the crustal deformation appear. When this wave is input to a seismograph having the concept of FIG. 37, a wave that is extremely difficult to analyze will be recorded.

In the case of the observation example of the present invention, the observation example of FIG. 18 corresponds to this. FIG. 18 shows observation data of an M = 7.7 earthquake with a hypocenter off New Guinea, which was observed by the earthquake sensor of the embodiment shown in FIG. 1 at 21:12 on April 21, 1997. The hypocenter distance is 613 in straight line distance.
It is 6 km and about 7,000 km on the map. Normally, at such a long distance, short-period waves having a period of 1 second or less are reduced, and only long-period components of the waves remain.
The sensor observing this is L = 30 cm, natural period 1.1
It has the characteristics of seconds. Judging this from the analysis result described above, this corresponds to the case where a wave sufficiently longer than the natural period is input to the sensor, and the sensor should function as an accelerometer. However, this seismic motion is not recorded in the acceleration type seismometer provided with the sensor of the present invention during the time period. Although the above-described theoretical analysis is an analysis result of only the x-axis or only the y-axis, it is a well-known fact that the pendulum is extremely sensitive to inclination in practice.

Considering that the seismic motion includes components such as inclination and rotation, it is easy to explain the detection characteristics of the earthquake sensor of the present invention shown in FIG. That is, the seismic sensor of the present invention has the degrees of freedom φ and θ shown in FIG.
It is considered that a wave motion corresponding to is detected. Above all, it is considered that they react extremely sharply to the inclination angle φ. It is considered that the wave including the inclination angle φ has a clear distance characteristic, which will be described later with reference to FIG. In other words, as inferred from the characteristics of FIG. 18, a relatively large-scale earthquake is accompanied by a long-period vertical motion, and its displacement is inevitably induced as ground inclination. The operation will be explained on the assumption that even the shortest one can react to the long-period component of the earthquake.

FIG. 19 shows the magnitude sensitivity characteristics (large-scale earthquake detection characteristics) of the earthquake sensor of the present invention. This graph plots an earthquake that occurred at a distance of 320 km to 350 km from the observation point. The vertical axis represents the recording length on the recording paper, and the horizontal axis represents the magnitude. Most of the epicenter of this earthquake was a swarm off the Izu Peninsula. In order to calibrate the present invention, it is considered that the best method is to obtain such a chance of a swarm earthquake and create a graph as shown in FIG. Now, from this graph, the relationship between the magnitude and the record length can be read, and the magnitude of an earthquake that occurred at a distance of 320 km to 350 km can be known. For example, if an M7.0 earthquake occurs at the above distance, it can be seen from FIG. 19 that the graph shows an overrange region at about M5.9 and a sensitive earthquake at the observation point. The record length of an earthquake of about M5.0 is about 10 mm.

If this graph is closely observed, the cut-off characteristics obtained by the optical noise and tremor removing means of the present invention can be clearly read. That is, the earthquake sensor according to the embodiment of the present invention is designed so as to be able to cut an earthquake of M3.5 or less generated at a hypocenter distance of 50 km. This numerical value is referred to as cutoff magnitude in the present invention. This cutoff magnitude tends to increase as the source distance increases. This is because the wave component of a certain period of the seismic wave, that is, the wave component of one second in the sensor according to the present embodiment is attenuated by the distance, so that when the distance exceeds a certain distance, the seismic wave contains many inclination components. The seismic sensor of the present invention has such characteristics because the tilt component is sensitively detected. As described above, the inclination component of a seismic wave is included in a relatively large-scale seismic wave, and a small-scale seismic wave, which is numerically M4.5 or less, has little inclination component. 19 and FIG. 20 to be described later.

It is considered that the above-mentioned certain distance can be obtained by preparing a graph shown in FIG. 20 and studying it in detail (the details will be described later). In another method, FIG.
Is calculated every 10 km or every 100 km, and this method is effective when a large amount of data is obtained. The characteristics obtained in this way are called long-distance earthquake detection characteristics. In the case of academic pendulum seismometers, such characteristics may hinder observation, and the natural period of the seismometers is intentionally extended.

On the other hand, in the present invention, as will be described later, by adjusting the natural period of the seismic sensor, the gradient component contained in the seismic wave is detected preferentially, and the presence or absence of the gradient component determines the magnitude of the earthquake. In addition to simplifying the complex electronic circuits and computer calculation methods required for waveform processing of seismic data, the reliability and mechanical strength of the equipment have been greatly improved. There are features. However, this distance characteristic does not need to be provided unless it is required for the sensor, and the present invention also includes the use of a broadband pendulum that responds to both the tilt component and the wave component.

FIG. 20 shows a measurement limit distance graph of the earthquake sensor of the present invention, which is called a cutoff range. This graph shows the measurement limit of the present invention, in which the vertical axis represents the hypocenter distance, and the horizontal axis represents the magnitude. Each data is recorded on a recording paper as 0.
Earthquakes with record lengths of 5 mm, 1.0 mm, 1.5 mm, and 2.0 mm. When these are plotted on a graph, a graph as shown in FIG. 20 can be obtained. Although FIG. 20 does not plot an earthquake of M3.2 or less, this is not because no earthquake has occurred, but it is a cutoff magnitude that is a feature of the present invention, that is, a cutoff of M3.5 at a distance of 50 km. This is because off exists in this region.

The magnitude of the earthquake at the minimum data point is approximately M3.2, and the magnitude of the cutoff magnitude is M3.5.
But it is not,
This is due to the above-described distance attenuation characteristics of the cutoff magnitude, and the cutoff magnitude has such a property that the cutoff magnitude has a property of decreasing as the hypocenter distance approaches. Further, the measurement limit of the earthquake sensor of the present invention can be read from FIG. For example, the measurement limit distance of an M7.0 earthquake is about 4 for a record length of 2.0 mm.
It is thought that an earthquake of M7.0 or less that occurred at a distance of 000 km and longer than that could not be detected.

By examining the graph of FIG.
It can be seen that these straight lines are not one straight line but change the slope of the graph halfway. This is estimated to be the distance at which the seismic wave having a period of one second attenuates as described above. This bend point has an epicenter distance of about 350
A seismic wave that exists in the range of km to 450 km (indicated as region A in FIG. 20) and whose epicenter distance exceeds 500 km is considered to contain many inclination components regardless of the magnitude of the magnitude M.

Normally, a large magnitude M earthquake has a tilt component and a large intensity, so that the value of M necessarily takes a large value. However, according to the inventor's experience, the magnitude of M is large before the Hyogoken Nanbu earthquake. Like a small earthquake that occurred, even though M was below the cutoff magnitude (3.5 or less), it exceeded the cutoff range (at a distance of 50k).
When an earthquake such as m.m. is detected, the seismic wave contains a large amount of tilt components, and is considered to be a precursor of a large-scale earthquake, and thus requires attention (for example, a distance of 50 in M3.3).
km is detected.)

In addition, the information obtained by combining the graphs of FIGS. 19 and 20 includes information important in geophysics, but a detailed description of this characteristic will be described. Since it deviates from the scope of the claims of the present invention, it is omitted here. The detection characteristics described above are merely examples, and the sensitivity characteristics shown in FIGS. 19 and 20 do not need to be particularly linear, but may be implemented in the scope of the present invention even if they are curves. It goes without saying that it is possible.

Next, a modified example of the above-described arrangement relationship between the pendulum and the light source will be described. FIG. 5 shows a modification of the arrangement relationship. In this case, the size relationship of the openings is that the opening A> the opening B, which is opposite to the size relationship of the openings described above. In any case, the same effect can be obtained in both the opening A and the opening B of the portion that swings due to the seismic motion. The intensity distribution of the light source 1 may be such that the central portion is strong and the peripheral portion is weak, as in a general light source. However, in the case where the opening is configured as described above, the light intensity distribution is completely flat,
The effect remains unchanged.

FIG. 6 is a basic form of the magnitude relation described above and is shown for reference. In order to increase the sensitivity, the size relationship between the openings A and B may be made tight as shown in FIG. However, in this case, it becomes difficult to remove the microtremor.

Further, an opening for removing fine movements is not always necessary. If the same relationship as this opening is established between the light source and the photodiode, FIGS.
As shown in FIG. That is, if the swing width of the pendulum is set to a small amount, the earthquake detection characteristics of the present invention can be obtained only by the magnitude relationship between the photodiode and the irradiation light flux generated by the light source. In this case, one of the light source 1 and the photodiode 14 needs to be on the pendulum side, and the other has to be on the fixed side. If only the vibration is detected, the positional relationship between all the optical components may be oscillated by the vibration. However, in such a case, it is considered that it is difficult to remove the fine movement.

The respective effects are as follows. FIG.
The light receiving area of the photodiode 14 is larger than the irradiation light flux 15 of the light source 1, and this relationship produces the same operation as that of the above-described opening. When the intensity distribution of the light source is substantially uniform, or when the light source has a uniform (may be a zebra pattern) transverse mode like a multi-mode laser, as shown in FIG. You just need to make it bigger. In this case, if the light source has an intensity distribution, it is possible to remove minor fluctuations in accordance with the geometric condition of the intensity distribution. That is, the pattern of the light source is
It does not need to be circular separately, but may have various shapes.

FIG. 10 shows a case where the sensitivity is increased. Thus, the size of the light source 1 and the photodiode 1
When the size of No. 4 is made tight, the sensitivity is increased, but at the same time, there is a possibility that it is difficult to remove the microtremors.

Although the function and effect of the present invention have been described only by the magnitude relationship between the light source and the photodiode as the light receiving element, this relationship is determined by using an image mask including an optical lens, a prism, an optical fiber, a filter, and a hologram. It can also be configured.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of the optical pendulum seismic sensor according to the present invention will be described with reference to FIGS. FIG. 21 shows a case in which an optical output end and an optical input end for removing optical microtremors of the sensor are constituted by optical fibers. Optical fibers having different core diameters and mode field diameters may be used, or optical fibers may be bundled to create a magnitude relationship. Regarding the position of the pendulum at this time, the pendulum may be provided on either the light source or the fiber as long as the same effect can be obtained in addition to the configuration shown in FIG.

When these optical fibers are used, the same functions and effects as those shown in FIGS. 5 to 10 can be obtained. For example, when the present invention is configured only with a single-core single-mode fiber, a fiber having a large mode field diameter is connected to the optical receiver side as shown in FIGS.
If a fiber having a small mode field diameter is arranged on the pendulum side, the standard configuration described above is obtained.

Since the mode field diameter here has the same meaning and effect as the core diameter in a multimode fiber, the present invention can be constituted by combining multimode fibers. If a single mode fiber is used as the optical fiber, it becomes possible to use a functional optical fiber doped with erbium, neodymium, praseodymium, etc., and it is possible to use the optical direct amplification function and the light stimulated emission function of the functional optical fiber. Therefore, the application range of the earthquake sensor is widened.

Specifically, the structure of a typical erbium-doped fiber has a Δn of 1.5 to 2.0%, a core diameter of 1.5 μm to 2.3 μm, and a mode field diameter of about 5 μm at this time. This optical fiber is called a high delta fiber. A general optical fiber for communication is a 1.3 μm optical transmission fiber, Δn is about 0.2%, and a mode field diameter is 10 μm. On the other hand, a fiber used for information transmission such as for a high-definition CATV. Is
The mainstream for 1.55 μm optical transmission is a low-dispersion fiber having a dual structure with an outer core diameter of 14 μm and an inner core diameter of 8 μm, which is called a dual-shaped core. The mode field diameter of this is 8 μm and Δ
n is about 1%. The cutoff of the 1.3 μm optical communication fiber is around 1.20 to 1.23 μm, and it is possible to transmit 1.55 μm light in a single mode using this.

That is, as can be seen from the above, the present invention can be constituted only by a single mode fiber, and the sensor of the present invention can be constituted entirely by optical components including signal amplification. In addition, a functional optical fiber or a single-mode fiber for communication can be drawn at high speed, so that carbon coating can be easily performed. The carbon coat effectively protects the optical fiber from static fatigue, chemical (salt damage), deterioration of optical performance due to hydrogen gas intrusion, etc., and greatly improves its durability. That is, when the earthquake sensor of the present invention is used in a volcanic zone or the like as a “sea bottom earthquake sensor” or “well earthquake sensor” or “spring well earthquake sensor”, it is particularly effective. Needless to say, it is possible to use an inexpensive plastic fiber.

FIG. 22 shows a case where a liquid crystal or the like representing an image (hologram or spatial filter) is used as an optical component, and FIGS. 23 (a) to 23 (d) show a case where an optical filter or a lens system is used. .

FIG. 23A shows an optical filter to which the above-mentioned magnitude relation is applied. Similarly, (b) is a graph in which the motion of the pendulum is converted into a rotation angle to obtain an earthquake detection characteristic between the fixed prism and the rotating prism. Is obtained by providing an optically parallel portion to the lens. (C) is a combination of numerical apertures of the lens system, in which the magnitude relation is replaced. In this case, a part of light escapes from the collimating lens to obtain an earthquake detection characteristic. (D) shows a combination of a lens system and a prism system, and the flat part formed in the prism part is used as a noise and fine movement removing means.

In each case, the respective structures are completely different, but these are modifications of the present invention, and as long as the pendulum is used as a seismic sensor, the operation and effect are not different from the above-mentioned case. The present invention can be embodied within the scope of the claims of the present invention. In the above description, transmitted light is mainly used, but displacement of the pendulum is measured, and
Reflected light or scattered light may be used if it is possible to remove the fine movement. FIG. 24 shows the positional relationship in that case. In this case, the effect of the present invention is the same.

As described above, the present invention is based on the optical system, and eliminates the fine movement due to the mutual geometrical arrangement of the light source side and the light receiving side which is an optical component including the photoelectric conversion element. There is a great feature in that it can be freely implemented in any form without depending on the shape of the device or the sensor. This feature is obtained by the ability to detect the movement of the pendulum in a non-contact manner by an optical method, and this high degree of freedom cannot be obtained by other electric seismic detection means. .

Another feature of the optical system is that the sensor can basically work on the safe side. For example, in the sensor having the structure shown in FIG. 1, when there is no vibration, the optical axis is kept constant, and the output of the photodiode at this time takes the maximum value. However, when an earthquake motion is detected, the optical axis shifts and the output of the photodiode decreases. At this time, if a large-scale seismic wave is input, the optical axis is completely deviated, and the output of the photodiode becomes zero (B contact operation). If the light source is lost for some reason or if the sensor and the control device are disconnected, the output from the sensor becomes zero, and it is possible to immediately know the abnormality of the device. The present invention can be configured to output a signal in the reverse case, that is, at the stage when an earthquake is detected (A-contact operation). Requires reliability of each component.

In addition, the optical pendulum earthquake sensor of the present invention has extremely high sensitivity, and is therefore affected by vibrations other than earthquakes and road construction. For example, vibrations associated with strong winds such as typhoons and tornadoes, and vibrations associated with disasters such as large-scale debris flows, landslides, and avalanches. Is detected. In this case, it is possible to exclude the output because it is not a seismic motion, but if such output is detected under a typhoon, heavy rain, or heavy snow, it is necessary to take evacuation action promptly. It is clear from consideration of past observations. Therefore, since these are also natural disasters, they cannot be excluded from the disaster prevention objectives of the present invention. Therefore, an observation method and an apparatus configuration will be described below using observation data.

First, FIG. 25 shows an effective system configuration for using the earthquake sensor of the present invention for disaster prevention. FIG. 25 is a diagram in which a weather sensor for measuring temperature, rainfall, wind direction and air pressure, and an earthquake sensor are connected to a data processing device. The data processing device is used to discriminate noise caused by an earthquake and wind. As for this discrimination method, the seismic wave measurement data obtained by the present invention may be decomposed in seconds, as shown in FIG. That is, in units of seconds, it is clearly decomposed into P waves and S waves as shown in the figure, and can be recognized as seismic waves.
In the case of long-distance seismic waves, it is possible to discriminate by the unit of time, but only in the case of huge earthquakes far away.

FIG. 27 shows observation data of an earthquake estimated to be accompanied by a tsunami that occurred on November 7, 1996 in the seas near Japan. Although this earthquake was unpublished and was not reported in newspapers, radio, or television, the observation data showed waveforms that suspected the occurrence of a tsunami, indicating the urgency and seriousness of the situation. In view of the above, the disclosure has been made herein. The hypocenter information is hypocenter estimation data that was transmitted by a US university on the Internet at the time of the observation, and the earthquake was observed at 5:00 am.
8.01 degrees (decimal), 143.70 degrees east longitude (decimal)
Met.

This corresponds to the Ogasawara Islands on the map, and the magnitude of the earthquake is M = 6.6 and the depth is h = 33 km. The epicenter is about 1050 km from the observation point. In other words, the characteristics of a tsunami earthquake with a large earthquake magnitude and a shallow epicenter are clearly shown, and a waveform estimated to be a tsunami has been continuously observed for about 4 hours since 8:00 am. Fortunately, the tsunami did not cause any damage, but if it was large-scale, the damage was expected to be large and there were no announcements in newspapers or television. It is considered that the earthquake can be detected only by the present invention.

It is the propagation speed that this data is estimated to be a tsunami. That is, seismic waves (including surface waves) are around 10 to 3 km per second,
This wave propagates over 1050 km in 4 hours, and the estimated speed is around 100 m / sec. According to past data, tsunami propagation speed is 200 km / h (60 m / s) to 400 km / h.
km (100 m / s), which coincides with the propagation speed estimated from FIG. Therefore, this wave is presumed to be the effect of the tsunami.

As described above, the present invention is strongly affected by strong winds caused by ocean waves and low pressures. FIG. 28 shows the observation data. This data is from July 26, 1997
The sensor according to the present invention records the effect of low pressure caused by typhoon No. 9 that has landed in the Kinki region early in the morning. In this observation data, a waveform estimated to be due to storm surge is recorded. That is, the typhoon is accompanied by the damage from the storm surge as well as the strong wind. When the observation data is read based on the article in the evening edition of the Mainichi Newspaper on July 26, the following can be understood. The evening edition of the Mainichi Shimbun reported that a car carrier Yamato Maru (discharge 8015 tons) was hit at 20 km offshore Shiomisaki at 6:10 am on the same day, causing damage. 30 minutes later at 6:40 am
Around a minute, a local government road patrol car in Kushimoto near Shiomisaki encountered high waves (approximately 7m), causing damage to the windshield.

Although these incidents seem at first glance, they are chronologically continuous and very interesting. If these are considered as a series of phenomena, the propagation speed of storm surge can be calculated. This propagation speed is about 11 m / s, or about 40 km / h. This corresponds to the propagation speed of waves (undulations). At the same time, at about 6:30, the sensor of the present invention catches a sudden change similar to an earthquake wave, as shown in FIG. ing. That is, it is considered that the storm surge reached the land at this time. Since the propagation speed of the seismic wave is about several kilometers per second near the surface of the earth, if the distance from Shiomisaki to the observation point is about 150 km, the wave arrives at the observation point in about 10 seconds, so this time difference can be ignored. The distance between the point where it is estimated that the road patrol car in Kushimoto has encountered high waves and Shiomisaki is about 5 to 10 minutes at 40 km / h. For these reasons, it is considered that the earthquake sensor of the present invention records the storm surge at Shiomisaki.

FIG. 29 shows the observation data of the debris flow. On this day, there was no wind and the weather was fine. So I checked and readjusted the optical axis.
This small vibration did not subside. With such a change, it was impossible to check the vibration of the pendulum with the naked eye, and we thought that there was a possibility that the optical sensor might break down.
Later research showed that this was related to the large-scale debris flow that occurred in the town of Otara-mura, Nagano Prefecture. According to the information obtained from the newspaper, the debris flow "started around 8 o'clock", which cannot be determined from the data. However, this waveform was recorded in the seismograph of the Japan Meteorological Agency, and the time of the maximum amplitude was around 10:41:10. That is, the time is the time at which the earthquake sensor recorded the maximum amplitude, and this is the main reason that this vibration is presumed to be related to the debris flow. On the map, there is a distance close to 200 km from the observation point to the debris flow generation site. However, since the sensor has extremely high sensitivity to such ground motion, the present invention requires that the sensor be within the vicinity of the disaster occurrence site (several hundred meters). If installed, it is considered to function effectively.

The sensor can also determine the presence or absence of aftershocks of an earthquake that occurred in an inland area in addition to a disaster involving ground vibration such as a debris flow or an avalanche. The observation data is shown in FIG. This is because M4.3 and M4.3 occurred at Toyohashi on March 16, 1997 at 14:53 and 15:36.
This is 3.9 earthquake observation data. If you look closely at the waveform, the aftershock that occurred later is superimposed on the vibration of the main shock and cannot be distinguished. In other words, when the earthquake sensor of the present invention is oscillating, it suggests that an aftershock may occur. If this information is used effectively, a secondary disaster due to an earthquake can be effectively prevented. it is conceivable that.

Next, FIGS. 31 to 35 show a system (disaster prevention alarm device) to be applied to the generation of these disaster prevention alarms.
Here is a recommended example of the disaster prevention warning judgment method. First, the data processing device of FIG. 25 described above may be configured as shown in FIG. This data processing device complements the drawbacks of the present invention, which are affected by wind and ocean waves as described above, and includes acceleration-type and speed-type ordinary (conventional) seismometers and weather sensors. Use in combination with. Signals input from these sensors are input to the alarm output determination unit, where the disaster prevention alarms are ranked.

This disaster prevention warning may be determined as follows based on the results described above. (1) If the optical seismic pendulum sensor does not detect an earthquake and an alarm is output from a conventional seismometer, it is determined that the earthquake is a small earthquake. (2) Optical seismic pendulum sensor detects the earthquake and
If a warning is output from a conventional seismometer, it is determined that the earthquake is a large-scale earthquake. (3) The optical earthquake pendulum sensor detects the earthquake, and
If the conventional seismometer does not issue a warning, it determines that the earthquake is a long-distance earthquake and warns of the possibility of tsunami, avalanche, debris flow, landslides, falling rocks, etc. (4) When the optical seismic pendulum sensor does not detect an earthquake and no alarm output is output from a conventional seismometer, it is determined that the apparatus is in a standby state. (5) If the output of the optical seismic pendulum sensor becomes 0, no alarm is output from the conventional seismometer, and if the optical seismic pendulum sensor does not recover after N hours or more, there is a possibility of equipment failure. Is displayed and a message prompting repair and inspection is displayed. And so on. When a weather sensor is added to this,
The influence wind speed Vw is set in consideration of the ground characteristics or based on actual measurement, and a judgment is added as follows.

When the wind velocity is equal to or higher than the affected wind speed Vw, the optical seismic pendulum sensor according to the present invention outputs an output corresponding to Vw of 1.3.
When there is a change of more than twice, the alarm operation of (1) to (5) is performed. Also, under the influence of Vw,
If the judgment is not possible, the warning action of the conventional seismometer is prioritized, and a warning is given for a strong wind. In this case, (5)
Is effective even under the influence of Vw.

The alarms obtained by these control operations are output to an alarm signal output distribution device, output to relays, buzzers, power switches of TVs and radios, broadcast equipment, alarm lights, etc. Warn of disasters.

The outline of the function of the data processing device has been described above. Next, FIG. 32 shows a recommended example of the device configuration around the optical pendulum earthquake sensor of the present invention. First, since an earthquake sensor is basically composed of a light source and a light receiving element,
An amplifier for the light receiving element and a light source driver for the light source are required.
In addition, in order to record the signal, it is convenient if there is a recorder such as a pen recorder. For example, LR4220 of Yokogawa Electric is most suitable.
The products of Anritsu, Ando, and Advantest are optimal for ILX and US made in Japan. Although the circuit may be assembled independently, it is safer for beginners to use the finished product. A signal from the amplifier is input to the CPU through a voltage comparison circuit and an A / D converter, and an earthquake is determined. It can also output an external control signal.

FIG. 33 shows an example in which the present invention is applied to an earthquake disaster prevention system for corporations and companies. In this system, the data processing device using the seismic sensor of the present invention is incorporated together with a measurement recording unit, and used in combination with a conventional seismometer. Data output from this system is connected and shared with a personal computer using a network. This network is best suited for Ethernet, FDDI
And token rings are expensive equipment and are difficult to install in the private sector. In addition, the use of Ethernet makes it easy to adopt the Internet protocol, and enables access to this system from all over the world.

This system does not exceed 5 million yen in price, and the price of each personal computer or server used in the network can be relatively low.
In addition, disaster prevention systems have been introduced in government agencies such as the Japan Meteorological Agency and the Fire Department, and research institutions such as universities, where abundant funds can be utilized and personnel with specialized knowledge are operating and managing them. Is expensive, and information from networks of governments and national universities was first carefully, carefully and carefully considered by officials, even in the event of a severe earthquake and severe damage. Later, it will be released on the Internet several hours to a month later. These pieces of information are currently the most powerful and accurate information generally available, but do not have real-time properties as in the present invention. Rather, such information can be used for the calibration of the present invention.

Next, FIG. 34 shows an earthquake alarm output device in which the system is simplified and reconfigured for home use. This device is
A recorder is omitted from the apparatus of FIG. 32, and a remote controller such as a television or a radio is attached to an alarm output (control signal) via a solenoid or an electronic switch. The sensor of the present invention can be used in such a manner since malfunctions are small if attention is paid to the installation location. With this device, in the event of a large-scale earthquake that occurred at a long distance, the TV can be switched on automatically, and the broadcasting station broadcasts earthquake information in a flash, so notify the residents of the occurrence of the disaster. Can be.

Next, FIG. 35 shows a case where the present invention is configured in a disaster prevention network using a personal computer. For this purpose, a local network such as Ethernet is used, and signals and measurement data from the respective seismometers and sensors are transmitted in text format as e-mail via a server or a router. The router is connected to a wired communication line and a mobile communication terminal such as a mobile phone or a satellite mobile phone, and is prepared for a disconnection of the wired communication. A computer for maintenance is separately connected to this network to prepare for daily data processing and network failures.

Finally, FIG. 36 shows the shape of a pendulum that can be used in the present invention. 36 (A) to (D) are suspension type pendulums which swing in the horizontal direction. (E) to (F) show an inverted pendulum that swings horizontally. In particular, (F) shows a pendulum mounted on a low rigidity material such as spring steel, and this spring steel has both restoration and vibration suppression. Vertical movement can be detected by the pendulums (G) to (I). In the above description, the horizontal movement has been mainly described, but by devising the shape of the pendulum in this way, the vertical movement can also be detected.

The embodiment described above is a recommended example to which the present invention can be effectively applied, and the photodiode is replaced with another photoelectric tube or light receiving element, or the CC is not used.
D can be changed to a circuit or means to which it is attached, or the opening can be integrated with the light source, and technical elements can be programmed, electronically circuitized, mechanized, means revised, materials changed, and Various modifications and changes, such as converting horizontal vibration to vertical vibration and measuring and detecting, can also be performed, as long as the microtremor removing means is performed by the geometrical arrangement of parts, it is implemented in the scope of the claims of the present invention. Is possible.

[0071]

As described above, according to the optical pendulum seismic sensor of the present invention, since a non-contact optical system is employed and an effective noise and tremor removing means is provided, an earthquake having a very high degree of freedom is provided. A sensor can be obtained and can be implemented in many forms including various modifications. In addition, the fine tremor removing means is changed to a high-sensitivity seismic sensor based on a primitive simple pendulum as shown in FIG. This sensitivity is
In the past, it could only be obtained with advanced seismometers that could only be owned by universities and the Meteorological Agency. As a result, even at the private level, it is possible to own an inexpensive, robust and low-cost high-sensitivity earthquake detection system and share disaster prevention information.

The sensor of the present invention is desirably installed underground, but it mainly functions with surface waves. Therefore, it is not necessary to install the sensor underground, and in the experiment, it was installed on the second floor of a wooden building. However, there is no malfunction. In addition, the accuracy of the sensor is not very necessary. If the relationship between the light source and the light-receiving element is appropriately selected, elementary and junior high school students can assemble as if they were science teaching materials. Another feature is that no special vocational training for assembly is required because the difference between the two does not affect the detection accuracy. This indicates that the sensor of the present invention is suitable for mass production.

Further, by constructing the disaster prevention alarm device of the present invention and employing the disaster prevention alarm judgment method, as described in each embodiment, false alarms can be eliminated from the conventional acceleration type seismometer. Becomes possible.

In addition, since the present invention is affected by ground motions such as waves and debris flows, it is possible to effectively protect the lives and property of the people from the danger of such disasters by conducting appropriate weather observations. became. In other words, in the past, the Meteorological Agency and the Fire and Disaster Management Agency issued warnings for disaster prevention.However, due to the special geographical conditions of Japan, disaster prevention information often did not reach some regions. Human lives and property were sometimes lost. On the other hand, according to the present invention, since high-sensitivity earthquake detection sensors at the research institution level can be provided to the private sector at low cost, these can be used for disaster prevention at the local or corporate level, such as in mountainous areas and remote islands. In this case, the effect of minimizing the damage caused by the disaster can be obtained.

If the present invention can be used as a science teaching material and widely spread, it is possible to raise the awareness of disaster prevention in the private sector, minimize the damage caused by earthquakes and other disasters, and save the lives of the people. It has the effect of protecting your property.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical pendulum earthquake sensor according to an embodiment of the present invention.

FIG. 2 is a functional equivalent configuration diagram of an optical miscellaneous movement removing unit.

FIG. 3 is a diagram showing an operation when an earthquake motion or a microtremor is added to the means.

FIG. 4 is a diagram showing an operation when a large seismic motion or small tremor is added to the means.

FIG. 5 is a diagram showing a modified example of the positional relationship between the pendulum and the light source.

FIG. 6 is a diagram showing a basic form of a size relationship between openings.

FIG. 7 is a diagram illustrating a case where the magnitude relation between openings is tight.

FIG. 8 is a diagram showing a relationship between a light receiving surface and an irradiation light beam of a light source.

FIG. 9 is a diagram showing a relationship between a light receiving surface and an irradiation light beam of a light source.

FIG. 10 is a diagram showing a relationship between a light receiving surface and an irradiation light beam of a light source.

FIG. 11 is a diagram showing an output waveform of a photodiode.

FIG. 12 is a diagram showing an earthquake record.

FIG. 13 shows an observation record of the earthquake by the earthquake sensor according to the present invention.

FIG. 14 is a diagram showing an earthquake record.

FIG. 15 is a diagram showing an observation record of the earthquake by the earthquake sensor according to the present invention.

FIG. 16 is a diagram showing an earthquake record.

FIG. 17 is a diagram showing an observation record of the earthquake by the earthquake sensor according to the present invention.

FIG. 18 is a diagram showing an example of observation by the earthquake sensor of the present invention.

FIG. 19 is a graph showing a magnitude sensitivity characteristic of the earthquake sensor of the present invention.

FIG. 20 is a diagram showing a measurement limit distance graph of the earthquake sensor of the present invention.

FIG. 21 is a configuration diagram in a case where an optical output end and an optical input end for removing optical noise and fine movement of a sensor are configured by optical fibers.

FIG. 22 is a configuration diagram in a case where an image is used for removing optical fine movements.

FIG. 23 is a configuration diagram when an optical filter and a lens system are used.

FIG. 24 is a configuration diagram when reflected light or scattered light is used.

FIG. 25 is a system configuration diagram for using an earthquake sensor for disaster prevention.

FIG. 26 is a diagram of seismic wave measurement data decomposed in seconds.

FIG. 27 is a diagram showing earthquake observation data obtained by the sensor of the present invention.

FIG. 28 is a diagram showing observation data obtained by the sensor of the present invention.

FIG. 29 is a diagram showing observation data obtained by the sensor of the present invention.

FIG. 30 is a diagram showing observation data obtained by the sensor of the present invention.

FIG. 31 is a configuration diagram of a data processing device in the disaster prevention alarm device.

FIG. 32 is a diagram showing a recommended example of a device configuration around the optical pendulum earthquake sensor of the present invention.

FIG. 33 is a configuration diagram in the case of an earthquake disaster prevention system.

FIG. 34 is a configuration diagram of an earthquake alarm output device reconfigured for home use.

FIG. 35 is a configuration diagram of a disaster prevention network.

FIG. 36 is a view showing a shape of a pendulum.

FIG. 37 is a diagram showing a pendulum model of the present invention used in the study.

FIG. 38 is a diagram showing degrees of freedom of a pendulum.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source 3 weight (pendulum type seismic motion detecting means) 4 perforated plate (optical miscellaneous motion removing means) 5 optical sensor (photoelectric signal converting means) 6 hanging wire 7 optical fiber 12 optical emitting means (optical misalignment removing Means) 13 Optical incidence means (Optical miscellaneous movement removing means) 14 Photodiode 15 Irradiation light beam

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G08B 21/00 G08B 21/00 F

Claims (3)

[Claims] 1. A photoelectric device which is attached to a pendulum which oscillates under the influence of various vibrations including an earthquake and converts light correlated with the vibration of the pendulum into a photoelectric signal based on light emitted from a light source. Pendulum-type seismic-motion detecting means for outputting an electrical signal by a signal converting means; incorporated in the pendulum-type seismic-motion detecting means, with respect to light from the light source, a lateral direction at an arbitrary angle with respect to a direction in which light propagates. And optical components that form one or more arbitrary images or graphic patterns that provide a light intensity distribution to the light components, and arbitrarily combine the light intensity distribution, magnitude relationship, and geometrical arrangement created by the arrangement of the optical components. An optical pendulum seismic sensor, comprising: optical miscellaneous tremor removing means for extracting only seismic waves from miscellaneous vibrations detected by the pendulum-type earthquake motion detecting means. 2. An optical seismic pendulum sensor, a control signal output device for monitoring a signal output of the optical seismic pendulum sensor and outputting an electric signal or an optical signal, and a conventional acceleration or velocity type seismometer A disaster prevention warning device characterized by determining the magnitude of an earthquake immediately before arrival of a main shock and outputting a warning by combining the above. 3. If the optical seismic pendulum sensor does not detect an earthquake and an alarm is output from the conventional seismometer, it is determined that the earthquake is a small-scale earthquake. , And, when an alarm is output from the conventional seismometer, it is determined that a large-scale earthquake, the optical seismic pendulum sensor detects the earthquake, and from the conventional seismometer If no warning is issued, the danger of tsunami is warned and it is determined that the earthquake is a long-distance earthquake.When the optical seismic pendulum sensor does not detect an earthquake and no alarm is output from the conventional seismometer Is a method for judging a disaster prevention alarm, wherein the method judges that the apparatus is in a standby state.