JPH06138244A - Measuring instrument for precursory vibration of earthquake - Google Patents

Abstract

PURPOSE:To provide earthquake prediction by measuring and computer- processing the high and low frequency band vibrations of the precursory phenomenon of earthquakes. CONSTITUTION:A water-immersed vibration sensor 1 is installed in a pipe reaching the bedrock of a fault plane where an earthquake is supposed to occur, to detect acoustic emission(AE) from a focal region and low frequency vibration, etc., that takes place just before the earthquake as electric signals. The electric signals are amplified by means of a preamplifier 3 and then separated using a high-pass filter 4 and a low-pass filter 5 into vibration levels of each band, and transmitted through an amplifier 6 and an A/D converter 7 and those data are transferred to an output controller 8 and a computer 9, which then makes calculations for earthquake prediction. A temperature sensor 2 performs remote measurement of the temperature rise of soil, etc., due to ultrasonic heating to supplement information about inland earthquakes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides information as one field of an earthquake prediction system by measuring high frequency band vibration and low frequency band vibration of the precursory phenomena of an earthquake and processing them by computer. is there.

[0002]

2. Description of the Related Art There is a method of catching a precursory vibration of an earthquake, a precursory earth current, etc. by a motion of a worm or the like, but it is not practically reliable. There is a method to make long-term prediction from the measurement data of the amount of movement of the observation points on the ground surface by accumulating many past data, and it has been proven as an effective method, but this method is short-term prediction (occurrence). (Date and time), currently, there is no direct connection. Earth current (earth potential)
The method of catching the precursory sign of an earthquake from the changes in the method is expected to be used particularly for short-term prediction (date and time of occurrence), but it has not been put to practical use yet. There is an earthquake forecasting method (Japanese Patent Publication No. 63-184088) by receiving a radio wave of an earthquake precursor. 2 of the main shock
Underground radio waves from the epicenter 5 weeks to 2 hours before
This is a method of forecasting by capturing with an underground antenna that reaches 00m to 1Km, which is similar to predicting from changes in the earth current (earth potential), but it avoids airborne noise waves and captures underground waves to This means that the estimation of the range has advanced considerably. However, regarding the date and time of occurrence, 2 weeks to 2
I want a little more accuracy during the time.

[0003]

First of all, it is difficult to distinguish an earthquake precursor from other causes by abnormal movements of snakes, worms, mice, chickens, etc. Seismic clouds, so-called Kurabiraiji, reaction potential difference of specific trees, etc. have their own results, but in order to be able to explain the relationship with long-term crustal deformation measurement data, seismic fault parameters, plate migration theory, etc. It will take a little longer. Even if the methods of long-term earthquake prediction are accumulated, it is difficult to estimate the date and time of occurrence. On the ground surface, there is a method of predicting by grasping changes in the earth current (earth potential) and the earth's magnetism.
It is difficult to specify the magnitude and the date and time of occurrence.

The present invention eliminates the drawbacks of the prior art and provides a measuring device for directly predicting an earthquake by a vibration sensor and processing it by computer to predict an earthquake. . In the laboratory, when performing a rock destructive test, attach a vibration sensor to the surface of the rock to capture acoustic emission (AE),
A method for calculating the position of the fracture surface by a computer has already been developed. Scale-independent destruction law (SC
ALE INVARIANT LAW) was established even for earthquakes, and there is a method of earthquake prediction on the extension line of the rock fracture test in the laboratory, but the other party is too large and there is a big problem in how to install the vibration sensor. It seems that he has rejected many challenges.

Geographical and geological conditions suitable for installation of vibration sensors 1. Wave noise is large on the coast, vibration noise from vehicles is large near the Shinkansen and highways, and noise is large in the industrial area for 24 hours, so avoid it if possible. 2. Go as deep as possible in the ground to eliminate natural noise and artificial noise as much as possible. 3. Since there are usually multiple faults that occurred as a result of past large earthquakes and appeared on the surface of the earth, considering the inclination of the fracture surface,
The location of pipes or deep wells must be set. 4. A rock or a deep well that reaches this rock will be installed by boring the rock that is in direct contact with the fractured surface of the rock (40 km x 20 km, for example) in the epicenter where a major earthquake is expected. The reliability decreases in the gravel layer and the rock-mixed layer. 5. It is said that the propagation resistance against ultrasonic vibration of groundwater is orders of magnitude smaller than that of rock mass, and if the fault part is filled with water, the ultrasonic vibration reaches farther than usual. It will be. It is also possible that ultrasonic vibrations starting from several tens of kilometers underground generate so-called cavitation locally in water due to its energy density, and secondarily generate ultrasonic vibrations at remote locations. Therefore, if a pipe or a deep well is set near the Chuo Tectonic Line, Itoigawa-Shizuoka Line and other various fault lines, vibration sensors will often be used in large ones.

[0006]

[Means for Solving the Problems] In order to remove noise caused by natural phenomena, social activities, etc., water is put inside deep wells, pipes, etc. of several tens of meters to several hundreds of meters underground to form a water immersion type vibration sensor group. Install a water immersion type temperature sensor. At least two types of signals in the high frequency band and low frequency band are digitally converted and processed by computer through input / output control. In order to remove the local noise and calculate the epicenter area, the data of other measuring devices of the same type will be connected to the communication line and used.

The configuration of the vibration sensor group is three or more on the same horizontal plane, and the orientation of the epicenter from the installation position is calculated. Furthermore, it is installed in the vertical direction and the depression angle of the epicenter from the installation position is calculated. The epicenter area can be calculated three-dimensionally by combining with the data of other measuring instruments of the same type.

After the A / D conversion of the vibration data, the raw data is temporarily stored in the storage device as it is. Raw data is averaged by the preprocessing subsystem and then processed in time series. The period in which the earthquake precursor appears is roughly divided into three, namely, an acceleration period, a sustaining period, and a transition period. Acceleration period: A period in which the occurrence of acoustic emission (AE) gradually increases. It usually starts a few days before the earthquake. When the set threshold is exceeded, a signal is output to the outside and the focal area is calculated. Persistence period: There is a large instantaneous variation in the level of occurrence of acoustic emission (AE), but even in the mountain type, the average level is maintained at about the same level. The magnitude of the earthquake is calculated based on the calculated value determined by the vibration level in this high frequency band and the rock quality of the epicenter. Especially in the case of a direct earthquake, the temperature of soil etc. will rise due to ultrasonic heating with the passage of time after the acceleration period. This temperature is as large as or higher than the seasonal variation, and is useful information for practical use. Transition period: It usually starts several hours before the earthquake, and should be called a precursory phenomenon of the earthquake rather than a precursory phenomenon. It shifts to low frequency vibration including low frequency vibration. Since the earthquake has already started partially, when the set threshold is exceeded, it is possible to calculate the date and time of the earthquake from the transitional regression curve and issue an emergency evacuation signal to the outside.

Since ultrasonic vibration of acoustic emission (AE) ultrasonically heats the soil between the epicenter and the ground, in the case of an inland earthquake, the temperature is about several degrees C higher than the normal average temperature. Changes in temperature due to rising
It is possible to continuously and remotely measure the temperature of soil, etc., which is not affected by precipitation, to catch the precursor of an inland earthquake.

[0010]

【Example】

(Specific example) Water is put inside a steel pipe reaching 25 m underground and a set of underwater PZT vibration sensors is installed here. Vibrations originating from the epicenter are transmitted from the rock and ground to the steel plate of the steel pipe pile. The vibration transmitted to the steel plate is accurately transmitted to the vibration sensor via the water inside the steel pipe. For non-destructive inspection of parts by ultrasonic waves, the water immersion angle method and the water penetration method are adopted depending on the shape and material, and the underwater ultrasonic sensor has a long track record and is highly reliable. The boundary value between the high band filter and the low band filter is 50 KHz. The time average is calculated as the preprocessing of the measurement data, but 10 seconds, 1 minute,
Calculate four average values for 15 minutes and 1 hour. As for the storage period of measurement data, in normal times, raw data is 48 hours, the average value is 1 week, and the data exceeding it is automatically cleared. If the threshold is exceeded, the data is stored on the computer cassette tape so that it can be accessed from the outside.

[0011]

EFFECT OF THE INVENTION The present invention directly applies high frequency band vibration (ultrasonic vibration) that occurs several days before the epicenter and low frequency band vibration (audible sound wave vibration and further low frequency vibration) that occurs immediately before an earthquake. Characterized by measurement and computer processing. By making use of this feature, it becomes possible to predict earthquakes, which were previously considered difficult, in a short period of time, and it is possible to issue a warning necessary for evacuation with a high probability, which is useful for protecting people's lives and property.

[Brief description of drawings]

FIG. 1 shows a connection method of a vibration sensor, a filter, an A / D converter, a computer and the like.

FIG. 2 shows a system for processing signals from vibration sensors.

[FIG. 3] This figure shows the characteristics of time-series changes of earthquake precursory vibrations.

[Explanation of symbols]

 1: Vibration sensor 2: Temperature sensor 3: Preamplifier 4: High band filter 5: Low band filter 6: Amplifier 7: A / D converter 8: Input / output control 9: Computer 10: Modem 11: Communication circuit

Claims (1)

[Claims] 1. An ultrasonic wave of acoustic emission (AE) generated by partial rock destruction as an earthquake precursor, and various vibrations including audible vibrations such as ground noise and sea noise immediately before the earthquake are captured, and these data are recorded by a computer. Process it. Measuring device for predicting earthquakes