阅读说明：本技术 地震发生预知方法以及地震发生预知系统 (Earthquake occurrence prediction method and earthquake occurrence prediction system ) 是由 近藤斋 榎本祐嗣 于 2020-04-17 设计创作，主要内容包括：提供一种地震发生预知方法以及地震发生预知系统。以低的费用负担来预知地震的发生。利用在地理上分散地设置的多个地下埋设构造物用电防蚀设备(30)来预知地震的发生。对在用于在各电防蚀设备(30)中进行电防蚀的闭环电回路(W)中流动的电流量的变化进行检测,基于所检测到的电流量的变化,预知地震的发生。(Provided are a method and a system for predicting earthquake occurrence. The occurrence of an earthquake is predicted with a low cost burden. An earthquake is predicted by using a plurality of electric corrosion prevention devices (30) for underground structures which are provided in a geographically dispersed manner. A change in the amount of current flowing through a closed loop circuit (W) for performing electrical corrosion protection in each electrical corrosion protection device (30) is detected, and the occurrence of an earthquake is predicted based on the detected change in the amount of current.)

1. An earthquake occurrence prediction method for predicting occurrence of an earthquake by using electric corrosion prevention devices for a plurality of underground buried structures which are geographically distributed, wherein a change in the amount of current flowing through a closed-loop circuit for performing electric corrosion prevention in each electric corrosion prevention device is detected, and occurrence of an earthquake is predicted based on the detected change in the amount of current.

2. The method of predicting occurrence of earthquake according to claim 1,

the electric corrosion protection device is an external power supply type electric corrosion protection device.

3. An earthquake occurrence prediction system for predicting occurrence of an earthquake by using electrical corrosion prevention equipment for a plurality of underground buried structures provided in a geographically dispersed manner, the earthquake occurrence prediction system comprising:

an observer that observes a change in the amount of current flowing in a closed-loop circuit for performing electrical corrosion prevention in each electrical corrosion prevention apparatus;

an information storage device that collects and stores information on a change in the amount of current observed by the observer and position information of the observer;

an information processing device which performs statistical processing on the stored information and outputs information related to earthquake prediction; and

and an earthquake information transmitting device for transmitting the output information related to the earthquake prediction.

Technical Field

The present invention relates to a method and a system for predicting occurrence of an earthquake.

Background

When quasi-static destruction occurs at a certain position of an earthquake-occurring region in the earth crust, destruction-induced charge emission occurs during the premonitory period of an earthquake, and when a detection electrode is disposed underground and a 2 nd electrode is disposed underground at or near the surface of the earth, although the reason is not necessarily clear, in practice, earth current flows between the detection electrode and the 2 nd electrode. In view of the above, a ground current detection device is known in which detection electrodes are disposed at a deep underground position so that artificial noise on the ground surface does not affect the detection result (see patent document 1). Therefore, when the earth current detection device is used, the earthquake prediction can be realized. However, in order to predict an earthquake, a large number of such earth current detection devices must be geographically distributed. However, the earth current detecting device is expensive, and there is a practical problem in that it is difficult to arrange a large number of the earth current detecting devices.

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have focused on an inland earthquake that may cause a serious disaster, and have started studies based on analysis of electromagnetic field changes inside the earth's crust when an earthquake occurs. The results were also based on experimental results, and the following conclusions were obtained: in inland subsurface earthquakes that occur as a result of the destruction of rock layers in the subsurface, when the rock begins to be destroyed, a negatively charged aggregate layer is formed on the surface side surface of the destroyed rock layers in the subsurface due to the interaction of the destroyed rock with deep gas, and a positively charged aggregate layer is formed near the surface due to the formation of this negatively charged aggregate layer (Yuji Enomoto, coupling of Earth circulation with deep Earth gaps: a passive properties for a semi-electromagnetic benzene, geological journal international, vol.191(2012) 1210-1214). When the positive charge aggregation layer is formed in the vicinity of the surface of the earth in this manner, the potential of the positive charge aggregation layer increases, and a current flows from the high-potential positive charge aggregation layer to the periphery of the low-potential positive charge aggregation layer in the vicinity of the surface of the earth. As a result, when a conductive underground buried structure is present, the current flows through the conductive underground buried structure.

The present inventors have focused on an electrical corrosion protection apparatus for electrically protecting an underground buried conductive structure. This is because: the electric corrosion protection apparatus includes a closed-loop circuit for performing electric corrosion protection, and when a current flows from the positive charge aggregate layer to the periphery of the positive charge aggregate layer as described above, the current flowing through the closed-loop circuit for performing electric corrosion protection changes due to an induced electric field generated in the closed-loop circuit. Also, the following conclusions were made: a large number of electric corrosion prevention apparatuses have been geographically distributed, and further, a closed loop electric circuit capable of capturing a change in an electromagnetic field inside the earth's crust upon destruction of a quasi-static rock layer in the form of a change in current (or voltage) has been formed in each electric corrosion prevention apparatus, and therefore, it is best to detect abnormal earthquake precursor signals caused by interaction of the destroyed rock with deep gas using these existing electric corrosion prevention apparatuses in anticipation of earthquake occurrence.

Means for solving the problems

Therefore, according to the invention of claim 1, there is provided an earthquake occurrence prediction method for predicting occurrence of an earthquake by using electric corrosion prevention devices for a plurality of underground buried structures which are geographically distributed, wherein a change in the amount of current flowing through a closed-loop circuit for performing electric corrosion prevention in each electric corrosion prevention device is detected, and the occurrence of the earthquake is predicted based on the detected change in the amount of abnormal current before the occurrence of the earthquake.

Further, according to the 2 nd aspect of the present invention, there is provided an earthquake occurrence prediction system for predicting occurrence of an earthquake by using electrical corrosion prevention devices for a plurality of underground buried structures provided geographically distributed, the earthquake occurrence prediction system comprising: an observer that observes a change in the amount of current flowing in a closed-loop circuit for performing electrical corrosion prevention in each electrical corrosion prevention apparatus; an information storage device that collects and stores information on a change in the amount of current observed by the observer and position information of the observer; an information processing device which performs statistical processing on the stored information and outputs information related to earthquake prediction; and an earthquake information transmitting device that transmits the output information on the earthquake prediction.

ADVANTAGEOUS EFFECTS OF INVENTION

Since the existing electric corrosion prevention equipment can be used, the prediction of the occurrence of an earthquake can be realized with a low cost burden.

Drawings

Fig. 1 is a diagram schematically showing the inside of the earth crust.

Fig. 2A and 2B are diagrams schematically showing an experimental method for confirming a change of an electromagnetic field inside the earth crust caused by an interaction of the destruction rock with the deep gas.

Fig. 3 is an overall view of the electric corrosion prevention apparatus.

Fig. 4 is a diagram for explaining the processing apparatus.

Fig. 5 is an overall view of other electrical erosion apparatus.

Fig. 6 is a graph showing a change in the amount of current flowing in the closed-loop circuit due to the interaction of the damaged rock with the deep gas (carbon dioxide).

Fig. 7 is a graph showing a change in the amount of current flowing in the closed-loop circuit due to the interaction of the damaged rock with the deep gas.

Fig. 8 is a diagram for explaining an average value of the amount of current flowing in the closed-loop circuit.

Fig. 9 is a diagram showing changes in the amount of current flowing in the closed-loop circuit.

Fig. 10 is a diagram showing changes in the amount of current flowing in the closed-loop circuit.

Fig. 11 is a flowchart for detecting an abnormality.

Fig. 12 is a diagram showing changes in the amount of current flowing in the closed-loop circuit.

Fig. 13 shows a graph of the change of the approximate straight line.

Fig. 14 is a flowchart for detecting an abnormality.

Fig. 15 is a flowchart for detecting an abnormality.

Fig. 16 is a diagram showing a change in an approximate straight line.

Fig. 17 is a flowchart for detecting an abnormality.

Fig. 18 is a flowchart for detecting an abnormality.

Fig. 19 is a schematic diagram of an earthquake occurrence prediction system.

Fig. 20 is a schematic diagram of an earthquake occurrence prediction system.

Description of the reference symbols

30 electric corrosion-proof equipment

31 metal tube

33 electrode

34 external power supply device

39 current meter

40 treatment device

80. 90 observer

81 information storage device

82 information processing apparatus

83 earthquake information transmitting device

W closed loop circuit

Detailed Description

First, a change in an electromagnetic field inside the earth crust due to an interaction between quasi-static destructive rocks and deep gas during a premonitory period of an earthquake immediately below the inland will be described with reference to fig. 1, 2A, and 2B. Fig. 1 is a diagram diagrammatically illustrating the inside of the earth crust, and fig. 2A and 2B diagrammatically illustrate an experimental method for confirming a change in an electromagnetic field inside the earth crust due to quasi-static destruction of rocks and deep gases. Referring to fig. 1, 1 denotes a ground surface, and 2 denotes a hard rock layer having crushed water retention pores existing at a depth of several tens Km or more from the ground surface. If a shear force acts in the rock layer 2 due to the movement of the block, the rock is quasi-statically broken, and fine cracks 3 are generated in the rock layer 2. At this time, electrons are released from the newly generated fracture surface of the rock, and negative charges are accumulated on the fracture surface of the rock. This quasi-static destructive process continues until the final destruction, i.e., the earthquake, occurs.

On the other hand, when a crack 3 is newly generated, deep gas such as carbon dioxide and methane flows through the crack 3, and at this time, the negative charge accumulated on the fracture surface of the rock charges the deep gas. The negatively charged deep gas gradually rises in the crack 3, and then flows out of the crack 3 as shown by an arrow and is retained on the surface 4 on the surface side of the rock layer 2. Next, as the number of the fine cracks 3 increases, the amount of the deep gas flowing out from each crack 3 increases, and as a result, as shown in fig. 1, a negatively charged aggregate layer 5 is formed on the surface 4 of the rock layer 2 in the deep underground. When the negatively charged aggregate layer 5 is formed on the surface 4 of the rock stratum 2, a positive charge is electrostatically induced in the vicinity of the surface 1 by the negative charge, and as a result, a positively charged aggregate layer 6 is formed in the vicinity of the surface 1.

Next, an experiment performed to verify a change in the electromagnetic field inside the earth crust due to quasi-static rock destruction will be described with reference to fig. 2A and 2B. In fig. 2A, 10 denotes a support base, 11 denotes a test rock placed on the support base 10, 12 denotes a jig, and 13 denotes a load cell (loadcell). A carbon dioxide gas flow hole 14 is formed in the jig 12, and high-pressure carbon dioxide gas is supplied to the inside of the inspection gas, for example, the carbon dioxide gas flow hole 14 as indicated by an arrow 15. When the jig 12 is pressed against the test rock 11 by the pressing device via the load cell 13, the crack 16 opens in the test rock 11 as shown in fig. 2A, and carbon dioxide flows out through the crack 16 as shown by an arrow 17. As a result of detecting the carbon dioxide flowing out of the crack 16, it was confirmed that the carbon dioxide was negatively charged.

On the other hand, in fig. 2B, a container 18 is used instead of the support table 10 shown in fig. 2A. A stainless steel pipe 19 coated with resin on the outer peripheral surface is inserted below the container 18, and the container 18 is filled with crushed stone and soil. In the case shown in fig. 2B, as in the case shown in fig. 2A, the jig 12 is pressed against the test rock 11 by the pressing device via the load cell 13, and when a crack 16 is generated in the test rock 11, carbon dioxide flows out from the crack 16. At this time, as a result of detecting the charged electric charge to the tube 19, it was confirmed that the tube 19 was positively charged.

From these experiments, it is believed that: when a fine crack 3 is generated in the rock layer 2 deep in the ground, as shown in fig. 1, a negative charge aggregate layer 5 is formed on the surface 4 of the rock layer 2, and a positive charge is electrostatically induced in the vicinity of the surface 1 by the negative charge, and as a result, it is confirmed that a positive charge aggregate layer 6 is formed in the vicinity of the surface 1. When a fine crack 3 is generated in the rock layer 2 deep in the ground in this way, a positively charged aggregate layer 6 is formed in the vicinity of the earth surface 1. As a result, the potential of the positively charged assembly layer 6 is higher than the potential around the positively charged assembly layer 6, and a potential difference is generated between the positively charged assembly layer 6 and the periphery of the positively charged assembly layer 6. Therefore, when the sign of occurrence of an earthquake occurs, a current flows from the high-potential positive charge aggregate layer 6 to the periphery of the low-potential positive charge aggregate layer 6 in the underground near the earth surface.

In addition, a large number of pipes for basic facilities such as gas pipes, water pipes, and petroleum pipelines are buried underground, and these large number of pipes are formed of conductive metal pipes, for example, stainless steel pipes. When such a metal pipe is buried in the ground, the outer wall surface of the metal pipe is gradually corroded by the local battery formed on the outer wall surface of the metal pipe. Since the metal pipe rapidly deteriorates when the outer wall surface of the metal pipe corrodes, corrosion of the outer wall surface of the metal pipe becomes a serious problem for the metal pipe buried in the ground. Therefore, although a synthetic resin for corrosion prevention, that is, corrosion prevention is usually applied to the outer peripheral surface of these metal pipes, corrosion cannot be prevented even in that case. Therefore, electric corrosion prevention equipment has been conventionally used to prevent corrosion of metal pipes.

Fig. 3 diagrammatically shows an example of the electrical erosion apparatus. In fig. 3, the electrical erosion apparatus is generally indicated by reference numeral 30. In fig. 3, 31 denotes a metal pipe for basic facilities such as a gas pipe, a water pipe, and a petroleum pipeline buried in the underground 32, and an outer peripheral surface of the metal pipe 31 is coated with a synthetic resin for corrosion prevention. The electric corrosion protection system 30 includes an electrode 33 made of, for example, cast iron, which is disposed in the underground 32 at a distance from the metal pipe 31, and an external power supply device 34 installed on, for example, the ground surface 35. The external power supply device 34 includes a power supply 36, and a negative terminal of the power supply 36 is connected to the metal pipe 31 via a lead 37. The positive terminal of the power source 36 is connected to the electrode 33 via a lead 38.

When a voltage is applied between the metal tube 31 and the electrode 33 by the power source 36, a minute anticorrosion current Y flows from the electrode 33 to the metal tube 31. By thus flowing the corrosion prevention current Y from the electrode 33 to the metal pipe 31, corrosion of the outer wall surface of the metal pipe 31 is prevented. Therefore, as can be seen from fig. 3, a closed loop circuit W is formed in the electric corrosion protection apparatus 3, which returns from the power source 36 to the power source 36 again through the lead 38, the electrode 33, the metal tube 31, and the lead 37. The electrical corrosion prevention system using the external power supply 36 is referred to as an external power supply system.

As described above, when the sign of the occurrence of an earthquake occurs, the positively charged aggregate layer 6 is formed near the surface of the earth, and a current flows from the positively charged aggregate layer 6 having a high potential to the periphery of the positively charged aggregate layer 6 having a low potential in the underground. At this time, when the closed loop circuit W shown in fig. 3 is formed, an induced electromotive force is generated in the closed loop circuit W due to the current flowing in the ground, and as a result, the current flowing in the closed loop circuit W increases. In addition, whether the current increased at this time flows in the closed-loop circuit W in the right turn or the left turn in fig. 3 is determined depending on which of the electrode 33 and the metal pipe 31 when the positive charge aggregation layer 6 having a high potential is formed has a high potential, and therefore, the direction of the current flow at this time differs for each galvanic corrosion protection device 30.

When such a sign of occurrence of an earthquake occurs, the amount of current flowing in the closed-loop circuit W changes. Therefore, by detecting a change in the amount of current flowing in the closed-loop circuit W, it is possible to predict the occurrence of an earthquake based on the detected change in the amount of current. The underground buried structure to be electrically protected by the electrical corrosion protection apparatus 30 is not limited to a metal pipe, and various steel materials such as a pier may be used. Therefore, the present invention can be used for an electric corrosion protection system for such an underground buried structure. Accordingly, in the present invention: an electric corrosion prevention system for an underground structure, which is provided in a geographically dispersed manner, detects a change in the amount of current flowing through a closed-loop circuit for performing electric corrosion prevention in each electric corrosion prevention system, and predicts the occurrence of an earthquake based on the detected change in the amount of current.

In order to detect a change in the amount of current flowing through the closed-loop circuit W, it is sufficient to dispose a detector 39, for example, an ammeter, for detecting the amount of current flowing through the closed-loop circuit W, as indicated by a broken line in fig. 3. As described above, in the present invention, since the occurrence of an earthquake can be predicted only by providing the current meter 39 in the existing electric erosion shield apparatus 30, the occurrence of an earthquake can be predicted with a low cost. In this case, in the embodiment shown in fig. 3, a processing device 40 for processing the detection value detected by the ammeter 39 is additionally provided in the electric erosion shield equipment 30 as shown by the broken line in addition to the ammeter 39. In this case, the occurrence of an earthquake can be predicted only by providing the detector 39 and the processing device 40 in the existing electric corrosion protection apparatus 30, and similarly, the occurrence of an earthquake can be predicted with a low cost.

Further, the change in the amount of current flowing in the closed-loop circuit W can be detected in various forms. For example, a change in the amount of current flowing in the closed-loop circuit W may be detected as a change in voltage. As described above, since the change in the amount of current flowing through the closed-loop circuit W is detected in the form of various detection values indicating the change in the amount of current flowing through the closed-loop circuit W, in the present invention, the detection values indicating the change in the amount of current flowing through the closed-loop circuit W include all of the various detection values indicating the change in the amount of current flowing through the closed-loop circuit W.

Next, the processing apparatus 40 shown in fig. 3 will be briefly described. The processing means 40 and the current meter 39 are shown in fig. 4. Referring to fig. 4, the processing device 40 includes an electronic control unit 41 and a communication device 42, and the electronic control unit 41 includes a microprocessor (CPU)43, a memory 44 as a storage device, and an input/output port 45, which are connected to each other via a bidirectional bus 42. As shown in fig. 4, the input/output port 45 is connected to the communication device 42, and the ammeter 39 is connected to the input/output port 45 via the AD converter 47.

Next, another example of the electrical erosion prevention apparatus 30 will be described with reference to fig. 5. In fig. 5, the same components as those in fig. 3 are denoted by the same reference numerals, and description thereof is omitted. Referring to fig. 5, the electric corrosion protection apparatus 30 includes an anode 50 disposed in the underground 32 at a distance from the metal pipe 31, and the anode 50 is connected to the metal pipe 31 via a lead 51. The anode 50 is formed of a metal having a higher ionization tendency than iron, such as aluminum. In addition, the anode 50 is surrounded by a mixture of fillers called backfill, such as gypsum, bentonite, and sodium sulfate.

In the electric corrosion prevention apparatus 30 shown in fig. 5, a minute current Y flows from the anode 50 to the metal pipe 31 due to a potential difference generated between the metal pipe 31 and the anode 50. By flowing the corrosion prevention current Y from the electrode 33 to the metal pipe 31 in this way, corrosion of the outer wall surface of the metal pipe 31 is prevented. In the electric corrosion protection apparatus 30, as shown in fig. 5, a closed-loop electric circuit W is formed in the electric corrosion protection apparatus 30, which returns from the metal pipe 31 to the metal pipe 31 again through the lead 51 and the anode 50. The galvanic corrosion prevention method using the potential difference generated between the metal pipe 31 and the anode 50 is referred to as a sacrificial anode method.

In the electrical erosion preventing apparatus 30 shown in fig. 5, when a current flows from the collection layer 6 of positive charges having a high potential to the periphery of the collection layer 6 of positive charges having a low potential in the ground in fig. 1, an induced electromotive force is generated in the closed-loop circuit W, and as a result, the current flowing in the closed-loop circuit W increases. Therefore, in the electric corrosion prevention device 30 shown in fig. 5, the occurrence of an earthquake can also be predicted based on the change in the amount of current flowing in the closed-loop electric circuit W. In the electric corrosion prevention device 30 shown in fig. 5, whether the increased current flows in the closed-loop circuit W in the right turn or the left turn in fig. 5 is determined depending on which of the metal pipe 31 and the anode 50 has a high potential when the positive charge accumulation layer 6 having a high potential is formed, and therefore, the direction of current flow at this time differs for each electric corrosion prevention device 30.

On the other hand, in the electric corrosion protection apparatus 30 shown in fig. 5, in order to detect a change in the amount of current flowing in the closed-loop circuit W, it is sufficient to arrange a detector 39, for example, an ammeter, for detecting the amount of current flowing in the closed-loop circuit W as indicated by a broken line in fig. 5. In this case, in the embodiment shown in fig. 5, as indicated by the broken line, the electric corrosion protection apparatus 30 is additionally provided with the detector 39 and the detection device 52 having the processing device 40 for processing the detection value detected by the detector 39. In addition, when an earthquake occurs, a high voltage is generated in the closed-loop circuit W due to an induced electromotive force. Therefore, it is preferable to use an external power supply type electric corrosion protection device that can also continue to operate at a voltage higher than the sacrificial anode type electric corrosion protection device 30.

Next, a change in the amount of current flowing through the closed-loop circuit W after the formation of the micro cracks 3 in the rock layer 2 has started, that is, after the quasi-static fracture has started, will be described with reference to fig. 6 to 9. Fig. 6 to 9 show a case where the etching resist current Y is continuously flowing. First, referring to fig. 6, the vertical axis I represents the amount of current flowing in the closed-loop circuit W, and the horizontal axis represents time. In addition, fig. 6 shows the time when quasi-static destruction starts and the time when actual destruction of the rock layer 2 occurs. On the other hand, in the underground, a slight natural current flows even when it is flat, I on the vertical axis I in fig. 6₀The natural current value at the normal time is shown. Fig. 6 shows, as an example, a case where the amount of current I flowing in the closed-loop circuit W detected by the detector 30 when the true failure occurs increases.

Referring to fig. 6, the amount of current I flowing through the closed-loop electric circuit W is a small value before the formation of the fine cracks 3 in the rock layer 2 starts, that is, before the quasi-static fracture starts. Next, when the generation of the fine crack 3 starts in the rock layer 2, that is, when the quasi-static fracture starts, the current amount I flowing through the closed-loop circuit W continuously changes at a slight value at first, starts to increase in the vicinity of time tX in fig. 6, and then rapidly increases to reach a peak, thereby achieving the true fracture. At this time, an earthquake occurs. Therefore, in fig. 6, if the time tX when the current amount I flowing through the closed loop circuit W starts to increase can be detected, the occurrence of an earthquake can be predicted. In the embodiment according to the present invention, the following are provided: the time tX at which the amount of current I flowing in the closed-loop circuit W starts to rise is detected.

Fig. 7 and 8 show a method for determining the rise start time tX of the current amount I used in the embodiment according to the present invention. First, referring to fig. 7, a curve F in fig. 7 shows a change in the current amount I in the section S in fig. 6, with the time axis being extended, and in fig. 7, Q1, Q2, Q3, and Q4 show a linear function for a predetermined time Δ t set in advance in succession_n-1、Δt_nThe change in the internal current amount I is approximated by an approximate function, i.e., an approximate straight line. On the other hand, fig. 8 is a detailed view of a portion related to the approximate straight lines Q1 and Q2 in fig. 7. Fig. 8 shows an actual change G in the current amount I and an average Im of the current amount I over a certain time Δ ts. In a specific example, the fixed time Δ ts is 10 seconds, and in this specific example, the average Im of the current amounts I during 10 seconds is obtained. Further, in this specific example, the average Im of the current amounts I is calculated every 10 seconds, and the constant time Δ t is set_n-1And Δ t_nSet to 2 minutes. Therefore, in this specific example, at a certain time Δ t_n-1、Δt_nAverage values Im of 6 current amounts I are obtained, and for each of approximate straight lines Q1, Q2, Q3 and Q4, a least square method is used according to a corresponding fixed time Deltat_n-1、Δt_nThe average Im of the 6 current amounts I obtained in the above step is obtained.

In addition, when the time Δ t is to be fixed_n-1The inclination of the inner approximate straight line (Q1, Q3 in FIG. 7) is K_n-1Will take a certain time Δ t_nThe inclination of the inner approximate straight line (Q2, Q4 in FIG. 7) is K_nIn the case of earthquake, the current amount I is increased only before the earthquake occursI slightly varies, and therefore, as shown in fig. 7, the inclination K of the approximate straight line Q1_n-1Substantially zero, inclination K of the approximate straight line Q2_nIs also substantially zero. Therefore, the inclination K of the approximate straight line Q2_nAnd an inclination K of an approximate straight line Q1_n-1The difference Δ K (═ K)_n－K_n-1) Is also substantially zero.

On the other hand, before the current amount I starts to increase due to the formation of the positively charged aggregate layer 6, as can be seen from the approximate straight line Q3 of fig. 7, the inclination K of the approximate straight line Q3_n-1Is substantially zero. On the other hand, when the amount of current I starts to increase due to the formation of the positively charged assembly layer 6, the inclination K of the approximate straight line Q4 is as shown by the approximate straight line Q4 in fig. 7_nBecomes larger. Therefore, at this time, the inclination K of the approximate straight line Q4_nInclination K to approximate straight line Q3_n-1The difference Δ K (═ K)_n－K_n-1) Becomes larger. In this case, in fig. 7, the fixed time Δ t used for obtaining the approximate straight line Q4_nWhen the start time tXs of (2) coincides with the rise start time tX of the current amount I, the inclination K of the approximate straight line Q4_nInclination K to approximate straight line Q3_n-1The difference Δ K (═ K)_n－K_n-1) The difference Δ K (K) becomes the maximum value at this time_n－K_n-1) Exceeding a threshold value alpha determined from past measured data. Therefore, in the embodiments of the present invention, the difference Δ K (═ K) is set_n－K_n-1) When the threshold value alpha is exceeded, the fixed time Δ t used for obtaining the approximate straight line Q4_nStart time tXs is set as a rise start time tX of current amount I.

Next, a method for calculating the rise start time tX of the current amount I used in the embodiment according to the present invention will be briefly described with reference to fig. 9. The curve F shown in fig. 9 is the same as the curve F shown in fig. 7. As described above, in the embodiment according to the present invention, for example, the average Im of the current amounts I flowing through the closed-loop electric circuit W is obtained every 10 seconds, and when the average Im of the current amounts I is obtained, the average Im of the current amounts I is obtained based on the time from when the average Im of the current amounts I is obtained to the fixed time Δ t_n+ a certain time Δ t_n-1The period up to beforeThe average Im of the current amounts I in (d) is calculated to obtain a difference Δ K (═ K)_n－K_n-1)。

That is, in fig. 9, at time t₁When the average value Im of the current I is obtained, the average value Im of the current I is obtained until a certain time delta t_n+ a certain time Δ t_n-1The average value Im of the current amounts I in the previous period is obtained to obtain an approximate straight line Q₁Inclination and Q₂From these gradients, the difference Δ K (═ K) is calculated_n－K_n-1). Then, at time t₂When the average value Im of the current I is obtained, the average value Im of the current I is obtained until a certain time delta t_n+ a certain time Δ t_n-1The average Im of the current amounts I in the previous period is obtained to obtain a primary straight line Q₃Inclination and Q₄From these gradients, the difference Δ K (═ K) is calculated_n－K_n-1). Hereinafter, at time t₃When the average value Im of the current I is obtained, at time t₄When the average value Im of the current I is obtained, at time t₅When the average value Im of the current I is obtained, at time t₆When the average value Im of the current I is obtained, at time t₇The same applies to the case where the average value Im of the current amount I is obtained.

When at each moment t₁、t₂、t₃、t₄、t₅、t₆、t₇The average Im of the current amounts I is obtained to calculate the difference Δ K (═ K)_n－K_n-1) When the difference is equal to Δ K, the difference is determined_n－K_n-1) Whether or not threshold value alpha has been exceeded, e.g. at time t₅Is discriminated as the difference Δ K (═ K)_n－K_n-1) When the threshold value alpha is exceeded, the time t₁Is set as the rise start time tX of the current amount I. When the average Im of the amounts of current I flowing through the closed-loop circuit W starts to rise, and then, when a certain time has elapsed, for example, after 30 to 40 minutes have elapsed, actual destruction in the rock layer 2 occurs, and an earthquake occurs. Therefore, if the rise start time tX of the average value Im of the current amount I is known, the occurrence of an earthquake can be predicted.

In addition, when an earthquake occurs after the average value Im of the current amount I starts to rise, the average value Im of the current amount I continues to rise until the actual destruction is reached. However, in a case where the increase in the average value Im of the current amount I is not due to an earthquake precursor, there is a case where the average value Im of the current amount I does not reach a true failure after the increase starts, that is, an earthquake does not occur. Therefore, even if the average Im of the current amount I starts to increase, a false alarm occurs when it is predicted that an earthquake will occur. In addition, if an earthquake does not occur after the average Im of the current amounts I starts to rise, the average Im of the current amounts I decreases in a short time thereafter. Therefore, whether or not an earthquake occurs can be determined from the trace of the average value Im of the current amount I after the average value Im of the current amount I starts to rise.

In the 1 st embodiment according to the present invention, the following are provided: when it is determined that the average Im of the current amounts I starts to rise, the increase amounts of the average Im of the current amounts I sequentially obtained from the time when it is determined that the average Im of the current amounts I starts to rise are integrated, and the integrated value Σ I of the increase amount of the average Im of the current amounts I is obtained. In this case, the increase amounts of the average value Im of the current amount I sequentially obtained from the time tX immediately after the start of the increase in the average value Im of the current amount I may be integrated. Further, when an earthquake occurs after the current amount I starts to rise, as shown by the solid line Z in fig. 9, the integrated value Σ I of the increase amount of the average value Im of the current amount I continues to rise, and when an earthquake does not occur after the average value Im of the current amount I starts to rise, the increase amount of the average value Im of the current amount I becomes negative, and therefore, as shown by the broken line in fig. 9, the integrated value Σ I of the increase amount of the average value Im of the current amount I decreases after the temporary rise. Therefore, in the embodiment according to the present invention, after the average value Im of the current amount I starts to rise, whether or not an earthquake occurs is determined based on whether or not the integrated value Σ I of the increase amount of the average value Im of the current amount I after a certain time has become equal to or less than the preset reference value dI shown in fig. 9.

On the other hand, fig. 10 shows a case where the amount of current I flowing through the closed-loop circuit W detected by the detector 30 when the true failure occurs is decreased, unlike the example shown in fig. 6. Note that since fig. 10 shows the same drawing as fig. 7, it is considered that the explanation of various symbols used in fig. 10 is not necessary, and therefore, the explanation of these symbols is omitted. In the case shown in fig. 10, when a fine crack 3 starts to develop in the rock layer 2, that is, when quasi-static fracture starts, the current amount I flowing through the closed-loop circuit W also continuously changes at a slight value at first. Next, the current amount I flowing through the closed-loop circuit W rapidly decreases after starting to decrease near time tXs in fig. 10, and the current amount I reaches a real breakdown. Therefore, in this case, if the time tXs at which the current amount I flowing through the closed-loop circuit W starts to decrease can be detected, the occurrence of an earthquake can be predicted.

In the case shown in fig. 10, before the current amount I starts to decrease due to the occurrence of an earthquake, the inclination K of the approximate straight line Q3 is determined from the approximate straight line Q3 in fig. 10_n-1Is also substantially zero. In contrast, when the current amount I starts to decrease due to the occurrence of an earthquake, the inclination K of the approximate straight line Q4 is determined as shown by the approximate straight line Q4 in fig. 10_nBecomes larger. Therefore, at this time, the inclination K of the approximate straight line Q4_nInclination K to approximate straight line Q3_n-1The difference Δ K (═ K)_n－K_n-1) The absolute value of the difference Δ K becomes negative. In this case, in fig. 10, the fixed time Δ t used for obtaining the approximate straight line Q4_nWhen the start time tXs of (2) coincides with the fall start time tXs of the current amount I, the inclination K of the approximate straight line Q4_nInclination K to approximate straight line Q3_n-1The difference Δ K (═ K)_n－K_n-1) Becomes maximum, and at this time, the difference Δ K (═ K)_n－K_n-1) Exceeds a threshold value alpha determined from past measured data. Therefore, considering the cases shown in fig. 7 and 10, in embodiment 1 according to the present invention, the difference Δ K (═ K) is set to be smaller than the case of the first embodiment_n－K_n-1) When the absolute value of (a) exceeds the threshold value alpha, a fixed time period deltat is used to obtain the approximate straight line Q4_nIs set to the current amount I start rising time tX or current amount I start down time tX, tXsThe falling time tX.

In the case shown in fig. 10, it is assumed that: when it is determined that the average Im of the current amounts I starts to decrease, the decrease amounts of the average Im of the current amounts I sequentially obtained from the time when it is determined that the average Im of the current amounts I starts to decrease are integrated, and an integrated value Σ I of the decrease amount of the average Im of the current amounts I is obtained. In this case, when an earthquake occurs after the current amount I starts to decrease, the integrated value Σ I of the decrease amount of the average value Im of the current amount I continuously decreases, and when an earthquake does not occur after the average value Im of the current amount I starts to decrease, the integrated value Σ I of the decrease amount of the average value Im of the current amount I increases. Therefore, in the embodiment according to the present invention, after the average value Im of the current amount I starts to decrease, whether or not an earthquake occurs is determined based on whether or not the integrated value Σ I of the amount of decrease in the average value Im of the current amount I after a certain time has become equal to or greater than the preset reference value — dI shown in fig. 9.

Fig. 11 shows an abnormality detection routine executed in the processing device 40 of fig. 4 to detect occurrence of an abnormality indicative of occurrence of an earthquake. The anomaly detection routine is executed by an interrupt every certain time, for example, every 4 msec.

Referring to fig. 11, first, at step 60, the amount of current I flowing through the closed-loop circuit W detected by the ammeter 39 is read, and the read amount of current I is stored in the memory 45. Next, at step 61, it is determined whether a fixed time Δ ts has elapsed, for example, whether 10 seconds have elapsed. When 10 seconds have not elapsed, the processing cycle is completed. On the other hand, when it is determined that 10 seconds have elapsed, the routine proceeds to step 62, where an average Im of the current amounts I is calculated, and the calculated average Im of the current amounts I is stored in the memory 45. Then, the process proceeds to step 63.

At step 63, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amounts I stored in the memory 45_n-1The average value Im of the current amounts I in the current storage. Next, in step 64, the fixed time Δ t is obtained by the least square method_n-1Internal current magnitude IAn approximation straight line for approximating the change of the average value Im of (a), and the inclination K of the approximation straight line is calculated_n-1. Next, at step 65, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amounts I stored in the memory 45_nThe average value Im of the current amounts I in the current storage. Next, in step 66, the time Δ t for a fixed time is obtained by the least square method_nAn approximate straight line for approximating the change of the average value Im of the current I in the current I is calculated_n。

Next, at step 67, it is determined whether or not an abnormality flag indicating that an abnormality indicative of occurrence of an earthquake has occurred is set (set). If it is determined that the abnormality flag is not set, the routine proceeds to step 68. In step 68, the calculated inclination K is determined_nAnd gradient K_n-1The difference Δ K (═ K)_n－K_n-1) Is over the threshold value alpha. When the difference is judged to be delta K (═ K)_n－K_n-1) If the absolute value of (a) does not exceed the threshold value alpha, the processing cycle is ended. On the other hand, the difference Δ K (K) is determined_n－K_n-1) If the absolute value of (a) exceeds the threshold value α, the routine proceeds to step 69, where an abnormality flag is set. Next, the process proceeds to step 70, where the average Im of the current amounts I is increased or decreased by an amount C.K_nThe initial value of (C is constant) is set to Σ I. The processing cycle is then ended. After the abnormality flag is set, in the next processing cycle, the flow proceeds from step 67 to step 71, where a fixed time Δ tS is added to the elapsed time tS. Since the initial value of the elapsed time tS is set to zero, the elapsed time tS indicates the difference Δ K (═ K) from the determination_n－K_n-1) The absolute value of (a) exceeds the threshold value alpha.

Next, in step 72, the increase or decrease C · K of the average value Im of the current amount I is added to the integrated value Σ I of the increase or decrease of the average value Im of the current amount I_n(C is a constant). Next, in step 73, it is determined whether or not the elapsed time t has elapsed a predetermined fixed time tSO, for example, 3 minutes. When the elapsed time tS has not elapsed a predetermined fixed time tSO, the processing cycle is ended. In contrast, at the elapsed time tWhen S has elapsed the predetermined fixed time tSO, the routine proceeds to step 74, where it is determined whether or not the integrated value Σ I of the increase amount of the average value Im of the current amount I is smaller than the predetermined reference value dI or whether or not the integrated value Σ I of the decrease amount of the average value Im of the current amount I is larger than the predetermined reference value-dI, that is, whether or not the integrated value Σ I of the increase amount or decrease amount of the average value Im of the current amount I is between the predetermined reference value dI and the set reference value-dI. When the increase amount or the decrease amount integrated value Σ I of the average value Im of the current amount I is between the preset reference value dI and the set reference value-dI, it is determined that no earthquake has occurred, and the routine proceeds to step 75, where the abnormality flag is reset. The processing cycle is then ended. When the abnormality flag is reset, the detection of the occurrence of an abnormality which is a sign of the occurrence of an earthquake is continued.

On the other hand, when it is determined in step 74 that the integrated value Σ I of the increase amount or the decrease amount of the average value Im of the current amount I does not fall between the preset reference value dI and the set reference value-dI, the routine proceeds to step 76, and a command to transmit various information on the earthquake is output to the communication device 42. That is, in step 76, a command to transmit an earthquake occurrence signal indicating occurrence of an earthquake is output to the communication device 42, and then, in step 77, a command to transmit an identification signal specific to the electric erosion shield equipment 30, for example, information on latitude and longitude of the installation position of the electric erosion shield equipment 30, and information on time such as the current time and the predicted time until the earthquake occurs is output to the communication device 42. Next, in step 78, a command to transmit information on the history of changes in the average value Im of the latest current amount I stored in the memory 45 is output to the communication device 42. Next, in step 79, a transmission command to transmit the average Im of the current amounts I at short time intervals in real time is output to the communication device 42.

Fig. 12 shows a modification of the embodiment shown in fig. 7 and 10 for determining the rise start time tX of the average value Im of the current amount I and the fall start time tX of the current amount I. In the modification shown in FIG. 12, K is defined as_n-1And K_nInstead of for a certain time at_n-1The inclination of the approximate straight line of the average value Im of the internal current amount I and the time Δ t for a certain time_nThe slope of the approximate straight line of the average value Im of the internal current amount I is used for a certain time Δ t_n-1Average value of current amount I and constant time Deltat_nAverage value of the current amount I in the capacitor. In this modification, the occurrence of an abnormality that is a sign of an earthquake occurrence can also be detected using the abnormality detection routine shown in fig. 11.

Next, embodiment 2 of the present invention for preventing erroneous judgment of occurrence of an earthquake will be described with reference to fig. 13 and 14. First, fig. 13 will be described, and a curve F shown in fig. 13 is the same as the curve F shown in fig. 9. In fig. 13, Q1, Q2, … …, Q19, and Q20 indicate a predetermined time Δ t for the series_n-1、Δt_nThe change of the average value Im of the current amounts I in the current loop is approximated to a straight line. In fig. 13, tX represents the start time of the rise of the average Im of the current amount I. In this embodiment 2, as in embodiment 1, when the average Im of the current amounts I flowing through the closed-loop circuit W is calculated every 10 seconds to obtain the average Im of the current amounts I, the average Im of the current amounts I is obtained based on the time from when the average Im of the current amounts I is obtained to the fixed time Δ t_n+ a certain time Δ t_n-1The average Im of the current amounts I in the previous periods is used to calculate the difference Δ K (═ K)_n－K_n-1)。

The changes of the approximate straight lines Q1, Q2, … …, Q19, and Q20 when the current amount I reaches the true destruction after the average value Im of the current amount I starts to rise are indicated by solid lines in fig. 13. As can be seen from the changes of the approximate straight lines Q1, Q2, … …, Q19, and Q20 indicated by the solid line in fig. 13, when the average value Im of the current amount I starts to increase, the difference Δ K (═ K) is obtained_n－K_n-1) Becomes equal to or more than a threshold value alpha, and a time delta t is set after the rise of the average value Im of the current amount I is started_nInner inclination K_nAnd time deltat_nInner inclination K_n-1The difference becomes small. Therefore, when the average value Im of the current amount I starts to rise and then reaches the true destruction, the difference Δ K (K) is obtained_n－K_n-1) After temporarily becoming equal to or higher than the threshold value α, the value of (d) is maintained to be small.

On the other hand, fig. 13 shows the changes of the approximate straight lines Q1, Q2, … …, Q19, and Q20 when the true destruction is not reached after the average value Im of the current amount I starts to rise. In this case, the average Im of the current amounts I increases first, but starts to decrease after a while after the start of the increase. Therefore, as is clear from the changes of the approximate straight lines Q1, Q2, … …, Q19, and Q20 indicated by the broken lines in fig. 13, when the average value Im of the current amount I does not reach the true destruction after the average value Im of the current amount I starts to rise, the difference Δ K (K) is obtained after the rise start time tX of the average value Im of the current amount I_n－K_n-1) After being maintained at the threshold value α or more, the value of (a) gradually decreases, for example, to minus α or less.

On the other hand, when the average value Im of the current amount I does not reach the true destruction state after the average value Im of the current amount I starts to decrease, the difference Δ K (K) is different from the case shown in fig. 13 after the decrease start time tX of the average value Im of the current amount I_n－K_n-1) After being maintained once at negative α or less, the value of (a) gradually increases, for example, to be equal to or greater than the threshold value α. Then, in this 2 nd embodiment: after the average value Im of the current amount I starts to decrease, the difference Δ K (═ K) is set within a certain time, for example, within 3 minutes_n－K_n-1) When the value of (d) is equal to or greater than the threshold value alpha, it is judged that no earthquake has occurred.

Fig. 14 and 15 show an abnormality detection routine executed in the processing device 40 of fig. 4 in order to execute the 2 nd embodiment. The anomaly detection routine is executed by an interrupt every certain time, for example, every 4 msec. Steps 80 to 87 in the routine shown in fig. 14 and 15 are the same as steps 60 to 67 in the routine shown in fig. 11.

That is, referring to fig. 14, first, at step 80, the amount of current I flowing through the closed loop circuit W detected by the ammeter 39 is read, and the read amount of current I is stored in the memory 45. Next, at step 81, it is determined whether or not a fixed time Δ ts has elapsed, for example, 10 seconds have elapsed. When 10 seconds have not elapsed, the processing cycle is completed. On the other hand, when it is determined that 10 seconds have elapsed, the routine proceeds to step 82, where an average Im of the current amounts I is calculated, and the calculated average Im of the current amounts I is stored in the memory 45. Then, the process proceeds to step 83.

In step 83, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amount I stored in the memory 45_n-1The average value Im of the current amounts I in the current storage. Next, in step 84, the time Δ t for a fixed time is obtained by using the least square method_n-1An approximate straight line for approximating the change of the average value Im of the current I in the current I is calculated_n-1. Next, at step 85, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amounts I stored in the memory 45_nThe average value Im of the current amounts I in the current storage. Next, in step 86, the time Δ t for a fixed time is obtained by the least square method_nAn approximate straight line for approximating the change of the average value Im of the current I in the current I is calculated_n。

Next, at step 87, it is determined whether or not an abnormality flag indicating occurrence of an earthquake as a sign is set. If it is determined that the abnormality flag is not set, the routine proceeds to step 88. In step 88, the calculated inclination K is determined_nAnd gradient K_n-1The difference Δ K (═ K)_n－K_n-1) Whether the threshold a is exceeded. When the difference is judged to be delta K (═ K)_n－K_n-1) If the value exceeds the threshold value alpha, the routine proceeds to step 89, where the calculated inclination K is determined_nAnd gradient K_n-1The difference Δ K (═ K)_n－K_n-1) Whether less than negative alpha. At a difference Δ K (═ K)_n－K_n-1) And when the alpha is not less than the negative alpha, ending the processing period.

On the other hand, at step 88, it is determined that the difference Δ K (═ K)_n－K_n-1) When the threshold α is exceeded, the routine proceeds to step 90, where a rise flag indicating the rise of the current amount I is set. Then, the process proceeds to step 92, where the exception flag is set, and the processing cycle ends. On the other hand, in step 89, it is determined that the difference Δ K (═ K)_n－K_n-1) When the current value is less than the negative alpha, the process proceeds to step 91, where the current value I risesThe up flag is reset. Then, the process proceeds to step 92, where the exception flag is set, and the processing cycle ends. After the abnormality flag is set, in the next processing cycle, the flow proceeds from step 87 to step 93, where a fixed time Δ tS is added to the elapsed time tS. Since the initial value of the elapsed time tS is set to zero, the elapsed time tS indicates the difference Δ K (═ K) from the determination_n－K_n-1) When the threshold α is exceeded, or the difference Δ K (K) is determined_n－K_n-1) Less than the elapsed time starting at negative alpha.

Next, in step 94, it is determined whether or not the elapsed time tS has elapsed a predetermined fixed time tSO, for example, 3 minutes. When the elapsed time tS has not elapsed for a predetermined fixed time tSO, the routine proceeds to step 95, where it is determined whether or not a rise flag indicating a rise in the current amount I is set. When the rise flag is set, the routine proceeds to step 96, where the difference Δ K (K) is determined_n－K_n-1) Whether or not it becomes smaller than negative alpha. At a difference Δ K (═ K)_n－K_n-1) When the time becomes smaller than minus α, it is judged that no earthquake has occurred, and the process proceeds to step 98, where the abnormality flag is reset. The processing cycle is then ended. When the abnormality flag is reset, the detection of the occurrence of an abnormality which is a sign of the occurrence of an earthquake is continued.

On the other hand, when it is determined in step 95 that the rise flag is not set, the process proceeds to step 97, where the difference Δ K (K) is determined_n－K_n-1) Whether the threshold a is exceeded. At a difference Δ K (═ K)_n－K_n-1) When the threshold value α is exceeded, it is judged that no earthquake has occurred, and the process proceeds to step 99, where the abnormality flag is reset. The processing cycle is then ended. When the abnormality flag is reset, the detection of the occurrence of an abnormality which is a sign of the occurrence of an earthquake is continued. On the other hand, when it is determined in step 94 that the elapsed time tS has elapsed the predetermined fixed time tSO, the routine proceeds to step 100, and a command to transmit various information on the earthquake is output to the communication device 42.

That is, in step 100, a command to transmit an earthquake occurrence signal indicating occurrence of an earthquake is output to the communication device 42, and then, in step 101, a command to transmit an identification signal specific to the electric corrosion prevention equipment 30, for example, information on latitude and longitude of the installation position of the electric corrosion prevention equipment 30, and information on time such as the current time and the predicted time until the earthquake occurs is output to the communication device 42. Next, in step 102, a command to transmit information on the history of changes in the average Im of the latest current amounts I stored in the memory 45 is output to the communication device 42. Next, in step 103, a transmission command to transmit the average Im of the current amounts I at short time intervals in real time is output to the communication device 42.

Next, embodiment 3 of the present invention for preventing erroneous judgment of occurrence of an earthquake will be described with reference to fig. 16 to 18. First, fig. 16 will be described, and a curve F shown in fig. 16 is the same as the curve F shown in fig. 9. In fig. 16, Q1, Q2, … …, Q19, and Q20 indicate a predetermined time Δ t for the series_n-1、Δt_nThe change of the average value Im of the current amounts I in the current loop is approximated to a straight line. In fig. 16, tX represents the start time of the rise of the average Im of the current amount I. In this embodiment 3, as in embodiments 1 and 2, when the average Im of the current amounts I flowing through the closed-loop circuit W is calculated every 10 seconds to obtain the average Im of the current amounts I, the average Im of the current amounts I is obtained based on the time from when the average Im of the current amounts I is obtained to the fixed time Δ t_n+ a certain time Δ t_n-1The average Im of the current amounts I in the previous periods is used to calculate the difference Δ K (═ K)_n－K_n-1)。

In fig. 16, similarly to fig. 13, the solid line indicates the change of the approximate straight lines Q1, Q2, … …, Q19, and Q20 at the time of the true breakdown after the absolute value of the average value Im of the current amount I starts to increase. When the average Im of the current amounts I starts to increase and then the current reaches the true destruction, the difference Δ K (K) is obtained as described above_n－K_n-1) After temporarily becoming equal to or higher than the threshold value α, the value of (d) is maintained to be small. On the other hand, when the average value Im of the current amount I reaches the true failure after the average value Im of the current amount I starts to rise, the time Δ t after the rise start time tX of the average value Im of the current amount I is reached_nInner inclination K_nIs maintained at a certain inclination or more.

In embodiment 3, the time Δ t after the rise start time tX of the average value Im of the current amount I is obtained_nInner inclination K_nTime Δ t of the rise start time tX of the average value Im of the current amount I_nInner inclination K_n-1Is set as a reference value K₀That is, in the example shown in fig. 16, the inclination K of the approximate straight line Q9_n-1Is set as a reference value K₀Then, the time Deltat after the rise start time tX of the average value Im of the current I is calculated_nInner inclination K_nAnd a reference value K₀The difference Δ KK (═ K)_n－K₀). After the rise start time tX of the average value Im of the current amount I, if the average value Im of the current amount I continues to rise, the gradient K_nIs maintained at a certain inclination or more, and therefore, the difference Δ KK (═ K)_n－K₀) The value of (A) is maintained at a constant value or more. Fig. 16 shows this difference Δ KK (═ K)_n－K₀)。

When the average value Im of the current amount I reaches the true destruction state after the average value Im of the current amount I starts to rise, the difference Δ KK (═ K) is obtained after the rise start time tX of the average value Im of the current amount I as shown by the solid line in fig. 16_n－K₀) Is maintained at a constant value, for example, around the threshold value α. On the other hand, if the average value Im of the current amount I does not reach the true destruction state after the start of the increase, the difference Δ KK (K) is obtained after a while from the start time tX of the increase of the average value Im of the current amount I_n－K₀) The value of (a) will decrease below the threshold value alpha. Then, in this 3 rd embodiment: when the average value Im of the current amount I starts to rise, the difference Δ KK (═ K)_n－K₀) If the value of (a) is maintained in the vicinity of the threshold value α for a certain time, for example, 5 minutes or more, it is determined that an earthquake has occurred, and the difference Δ KK (K) is obtained after the average value Im of the current amount I starts to rise_n－K₀) If the value of (d) is reduced to the threshold value alpha or less within a certain time, for example, within 5 minutes, it is judged that no earthquake has occurred.

On the other hand, the true value of the average Im of the current amounts I is reached after the average Im begins to decreaseAt the time of destruction, as shown by a broken line in fig. 16, the difference Δ KK (K) is obtained after the time tX when the average value Im of the current amount I starts to fall_n－K₀) Is maintained at a constant value, for example, around negative α. On the other hand, when the average value Im of the current amount I does not reach the true destruction state after the average value Im of the current amount I starts to decrease, the difference Δ KK (K) is obtained after a while after the start time tX of the decrease of the average value Im of the current amount I_n－K₀) Rises above negative alpha. Therefore, in this 3 rd embodiment: when the average value Im of the current amount I starts to decrease, the difference Δ KK (═ K) is obtained_n－K₀) If the value of (a) is maintained in the vicinity of negative α for a certain time, for example, 5 minutes or more, it is determined that an earthquake has occurred, and after the average value Im of the current amount I starts to decrease, the difference Δ KK (═ K) is obtained_n－K₀) If the value of (d) rises to minus α or more within a certain time, for example, 5 minutes, it is judged that no earthquake has occurred.

Fig. 17 and 18 show an abnormality detection routine executed in the processing device 40 of fig. 4 in order to execute the 3 rd embodiment. The anomaly detection routine is executed by an interrupt every certain time, for example, every 4 msec. Steps 110 to 121 in the routine shown in FIGS. 17 and 18 are the same as steps 80 to 91 in the routine shown in FIG. 14.

That is, referring to fig. 17, first, at step 110, the amount of current I flowing through the closed loop circuit W detected by the ammeter 39 is read, and the read amount of current I is stored in the memory 45. Next, in step 111, it is determined whether a fixed time Δ ts has elapsed, for example, whether 10 seconds have elapsed. When 10 seconds have not elapsed, the processing cycle is completed. On the other hand, when it is determined that 10 seconds have elapsed, the routine proceeds to step 112, where an average Im of the current amounts I is calculated, and the calculated average Im of the current amounts I is stored in the memory 45. Then, the process proceeds to step 113.

At step 113, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amount I stored in the memory 45_n-1The average value Im of the current amounts I in the current storage. Next, in step 114, the fixed time Δ t is obtained by the least square method_n-1Average of internal current IAn approximation straight line for approximating the change of the mean Im, and the inclination K of the approximation straight line is calculated_n-1. Next, at step 115, the constant time Δ t described with reference to fig. 8 is read from the average value Im of the current amounts I stored in the memory 45_nThe average value Im of the current amounts I in the current storage. Next, in step 116, the time Δ t for a fixed time is obtained by using the least square method_nAn approximate straight line for approximating the change of the average value Im of the current I in the current I is calculated_n。

Next, at step 117, it is determined whether or not an abnormality flag indicating that an abnormality indicative of occurrence of an earthquake has occurred is set. If it is determined that the abnormality flag is not set, the routine proceeds to step 118. In step 118, the calculated inclination K is determined_nAnd gradient K_n-1The difference Δ K (═ K)_n－K_n-1) Whether the threshold a is exceeded. When the difference is judged to be delta K (═ K)_n－K_n-1) If the value does not exceed the threshold value alpha, the routine proceeds to step 119, where the calculated gradient K is determined_nAnd gradient K_n-1The difference Δ K (═ K)_n－K_n-1) Whether less than negative alpha. At a difference Δ K (═ K)_n－K_n-1) And when the value is not less than the negative alpha, ending the processing period.

On the other hand, at step 118, it is determined that the difference Δ K (═ K) is present_n－K_n-1) When the threshold value α is exceeded, the routine proceeds to step 120, where a rise flag indicating the rise of the current amount I is set. Subsequently, the process proceeds to step 122, where the inclination K calculated in step 114_n-1Is set as a reference value K₀. Then, the process proceeds to step 123, where the exception flag is set, and the processing cycle ends. On the other hand, at step 119, it is determined that the difference Δ K (═ K)_n－K_n-1) If the current value is less than negative α, the routine proceeds to step 121, where the rising flag indicating the rise in the current amount I is reset. Subsequently, the process proceeds to step 122, where the inclination K calculated in step 114_n-1Is set as a reference value K₀. Then, the process proceeds to step 123, where the exception flag is set, and the processing cycle ends. When the abnormality flag is set, the process proceeds from step 117 to step 124 in the next processing cycle, and a fixed time Δ tS is added to the elapsed time tS. In addition, the method can be used for producing a composite materialSince the initial value of the elapsed time tS is set to zero, the elapsed time tS indicates the difference Δ K (═ K) from the determination_n－K_n-1) When the threshold α is exceeded, or the difference Δ K (K) is determined_n－K_n-1) Less than the elapsed time starting at negative alpha.

Next, in step 125, it is determined whether or not the elapsed time tS has elapsed a predetermined fixed time tSU, for example, 5 minutes. When the elapsed time tS has not elapsed for the predetermined fixed time tSU, the routine proceeds to step 126, where it is determined whether or not the rise flag indicating the rise in the current amount I is set. When the rise flag is set, the routine proceeds to step 127, where the difference Δ KK (═ K) is calculated_n－K₀) Next, the routine proceeds to step 128, where the difference Δ KK (═ K) is determined_n－K₀) Whether or not the difference is between a value α -s obtained by subtracting a small constant value s from the threshold value α and a value α + s obtained by adding a small constant value s to the threshold value α, that is, the difference Δ KK (═ K)_n－K₀) Whether or not it is a value near the threshold value alpha. At a difference of Δ KK (═ K)_n－K₀) If the signal is not between α -s and α + s, it is judged that no earthquake has occurred, and the process proceeds to step 131, where the abnormality flag is reset. The processing cycle is then ended. When the abnormality flag is reset, the detection of the occurrence of an abnormality which is a sign of the occurrence of an earthquake is continued.

On the other hand, when it is determined in step 126 that the rise flag is not set, the routine proceeds to step 129, where the difference Δ KK (K) is calculated_n－K₀) Next, the process proceeds to step 130, where the difference Δ KK (═ K) is determined_n－K₀) Whether or not the difference is between- α -s obtained by subtracting a small constant value s from- α and- α + s obtained by adding a small constant value s to- α, that is, the difference Δ KK (═ K-_n－K₀) Whether it is a value around-alpha. At a difference of Δ KK (═ K)_n－K₀) If the signal is not between- α -s and- α + s, it is judged that no earthquake has occurred, and the process proceeds to step 132, where the abnormal flag is reset. The processing cycle is then ended. When the abnormality flag is reset, the detection of the occurrence of an abnormality which is a sign of the occurrence of an earthquake is continued. On the other hand, in step 125, it is determined that the elapsed time tS has elapsed a predetermined fixed time tSU, that is, the difference Δ KK (═ K)_n－K₀) When the difference between α -s and α + s is maintained for a predetermined time period tSU or more, or the difference Δ KK (═ K)_n－K₀) When the time period tSU is maintained between- α -s and- α + s, the process proceeds to step 133, and an instruction to transmit various information related to the earthquake is output to the communication device 42.

That is, in step 133, a command to transmit an earthquake occurrence signal indicating occurrence of an earthquake is output to the communication device 42, and then, in step 134, a command to transmit an identification signal unique to the electric erosion shield equipment 30, for example, information on latitude and longitude of the installation position of the electric erosion shield equipment 30, and information on time such as the current time and the predicted time until the earthquake occurs is output to the communication device 42. Next, in step 135, a command to transmit information on the history of changes in the average Im of the latest current amounts I stored in the memory 45 is output to the communication device 42. Next, in step 136, a transmission command to transmit the average Im of the current amounts I in real time at short time intervals is output to the communication device 42.

Further, as described above, when the occurrence of an abnormality that is a sign of the occurrence of an earthquake is detected, a command to generate various information on the earthquake is output from the processing device 40 provided in each electrical erosion protection apparatus 30 to the communication device 42. In this case, in the embodiment of the present invention, the occurrence of an earthquake is predicted based on various information about the earthquake transmitted from the communication device 42 in each electrical erosion protection apparatus 30. Next, an outline of an earthquake occurrence prediction system for predicting the occurrence of an earthquake will be briefly described.

In the earthquake occurrence prediction system according to the present invention, the occurrence of an earthquake is predicted by using a plurality of electrical corrosion prevention devices 30 for an underground buried structure which are provided in a geographically dispersed manner. In this case, as shown in fig. 19, the earthquake occurrence prediction system includes: an observer 80 that observes a change in the amount of current I flowing in the closed-loop electric circuit W for performing electric corrosion prevention in each electric corrosion prevention device 30; an information storage device 81 that collects and stores information on a change in the amount of current I observed by the observer 80 and position information of the observer 80; an information processing device 82 that performs statistical processing on the stored information and outputs information on earthquake prediction; and an earthquake information transmitting device 83 that transmits the output information on the earthquake prediction. The information about the earthquake prediction transmitted from the earthquake information transmitting device 83 is received by a terminal 84 such as a mobile phone.

In this case, in the example shown in fig. 4, the observer 80 in fig. 19 corresponds to the ammeter 39 and the processing device 40. The information storage device 81 collects information on changes in the current amount I observed by a large number of geographically distributed observers 80 and position information of a large number of geographically distributed observers 80, and stores the information in a memory provided in the information storage device 81. The information processing device 82 predicts the location of occurrence of an earthquake, the scale of the earthquake, the time of occurrence of the earthquake, and the like based on various information stored in the memory of the information storage device 81, and the location of occurrence of the earthquake, the scale of the earthquake, the time of occurrence of the earthquake, and the like are transmitted from the earthquake information transmitting device 83 to the terminal 84 such as a mobile phone. For example, in the case of the embodiment shown in fig. 17 and 18 as an example, the difference Δ KK (═ K) is determined in a plurality of observers 80 that are close to each other_n－K₀) When the difference is maintained between α -s and α + s for a certain time period tSU or more, or the difference Δ KK (═ K)_n－K₀) When the time tSU is maintained between- α -s and- α + s, the earthquake with the highest earthquake intensity is predicted to occur in the area where the plurality of observers 80 are provided, and an earthquake alarm is immediately issued.

On the other hand, fig. 20 shows a schematic diagram of an earthquake occurrence prediction system using a network of an existing mobile phone. Similarly to the example shown in fig. 19, the observer 90 shown in fig. 20 corresponds to the ammeter 39 and the processing device 40. In this earthquake occurrence prediction system, information on changes in the amount of current I observed by a large number of observers 90 arranged geographically dispersedly and position information of a large number of observers 90 arranged geographically dispersedly are transmitted to the base station 91, and the information received in the base station 91 is sent to the server 93 via the network 92 of the portable telephone.

As shown in fig. 20, the server 93 includes a microprocessor (CPU)94 and a memory 95 as a storage device, and information sent from the base station 91 to the server 93 via the network 92 of the mobile phone, that is, information on the change in the current amount I observed by the large number of observers 90 and the position information of the large number of observers 90 are stored in the memory 95. The server 93 predicts the location of occurrence of an earthquake, the scale of the earthquake, the time of occurrence of the earthquake, and the like based on various information stored in the memory 95, and the location of occurrence of the earthquake, the scale of the earthquake, the time of occurrence of the earthquake, and the like are transmitted from the server 93 to the terminal 96 such as a mobile phone via the network 92 of the mobile phone and the base station 91.