Seismic sensor and earthquake detection method, earthquake detection program

Abstract

To provide a seismic sensor, earthquake detection method and earthquake detection program, each enabling accurate determination whether detected vibrations are from an earthquake or noise.SOLUTION: A seismic sensor 10 comprises: an acceleration acquisition unit 21; an acceleration waveform generation unit 22; a feature point extraction unit 25a; a score calculation unit 25b; and an earthquake determination unit 26. The acceleration acquisition unit 21 detects vibrations and acquires acceleration of the vibrations. The acceleration waveform generation unit 22 generates an acceleration waveform representing a relation between the acceleration measured by the acceleration acquisition unit 21 and an elapsed time. The feature point extraction unit 25a extracts feature points which appear as earthquake characteristics from the acceleration waveform generated by the acceleration waveform generation unit 22. The score calculation unit 25b calculates scores of the feature points extracted by the feature point extraction unit 25a. The earthquake determination unit 26 determines whether or not the vibrations are from an earthquake on the basis of a total value of the scores of the plurality of feature points calculated by the score calculation unit 25b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a seismic sensor for detecting seismic motion, an earthquake detection method, and an earthquake detection program. [Background technology]

[0002] In recent years, seismic sensors have been used that are built into gas meters, electricity meters, distribution boards, outlets, etc., and that output a cut-off signal to cut off the supply of gas, electricity, etc. when they detect earthquake motion of a magnitude above a predetermined value (for example, seismic intensity 5 or higher). For example, Patent Document 1 discloses a seismic sensor that outputs a shutoff signal when an index value indicating the magnitude of an earthquake is equal to or greater than a threshold value during an earthquake processing period following a judgment period, and that includes a continuing earthquake judgment unit that judges whether an earthquake has occurred based on the acceleration measured during the earthquake processing period, and a shutoff judgment unit that prevents the shutoff signal from being output regardless of the index value when the continuing earthquake judgment unit judges that an earthquake has not occurred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6465257 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional seismic sensors have the following problems. In other words, with the seismic sensor disclosed in the above publication, if the detected vibration has even the slightest noise characteristics, there is a risk that the vibration will be mistakenly determined to be noise. Furthermore, because the characteristics of the noise change depending on the device to which the seismic sensor is attached and the installation environment, it is difficult to accurately detect noise, and there is a risk that the noise will be mistakenly determined to be an earthquake.

[0005] An object of the present invention is to provide a seismic sensor, an earthquake detection method, and an earthquake detection program that can accurately determine whether a detected vibration is an earthquake or noise. [Means for solving the problem]

[0006] The seismic sensor according to the first invention comprises an acceleration acquisition unit, an acceleration waveform generation unit, a feature point extraction unit, a score calculation unit, and an earthquake determination unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation unit generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition unit and elapsed time. The feature point extraction unit extracts feature points that appear as characteristics of an earthquake from the acceleration waveform generated by the acceleration waveform generation unit. The score calculation unit calculates scores for the feature points extracted by the feature point extraction unit. The earthquake determination unit determines whether the vibrations are an earthquake based on the scores for the feature points calculated by the score calculation unit. Here, a seismic sensor uses an acceleration waveform formed based on the acceleration of the detected vibration to determine whether the vibration is an earthquake or not, and determines whether the detected vibration is an earthquake or not based on the score of the feature points calculated by extracting feature points that appear as characteristics of an earthquake in the acceleration waveform.

[0007] Here, this seismic sensor is mounted on, for example, an energy measuring instrument for gas, electricity, etc., and is installed to stop the supply of energy if it detects an earthquake of a predetermined seismic intensity or higher. Characteristics of earthquakes that appear in acceleration waveforms include, for example, low-frequency vibrations and non-linear motions in the acceleration waveform, the absence of non-vibration periods (periods when vibrations are stopped), and non-periodic motions exceeding a certain percentage. This allows for the extraction of characteristic points that appear in earthquake vibrations from the acceleration waveform of the detected vibrations, and for the determination of whether the detected vibrations are an earthquake or noise based on the total score of those characteristic points, thereby enabling earthquake determination to be performed by combining various characteristic points that appear in the acceleration waveform of the earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0008] A seismic sensor according to a second aspect of the present invention is the seismic sensor according to the first aspect of the present invention, wherein the feature point extracting section extracts the inclusion of low frequency vibrations in the acceleration waveform as a feature point. This makes it possible to accurately determine whether the detected vibration is an earthquake or noise by detecting the presence or absence of low-frequency vibrations that characteristically appear in acceleration waveforms that indicate an earthquake.

[0009] A seismic sensor according to a third aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, wherein the feature point extracting section extracts, as a feature point, that the acceleration waveform contains non-linear motion. This makes it possible to accurately determine whether the detected vibration is an earthquake or noise by detecting the presence or absence of non-linear motion that characteristically appears in the acceleration waveform indicating an earthquake.

[0010] The seismic sensor of the fourth invention is a seismic sensor of the first or second invention, wherein the feature point extraction unit extracts as a feature point when the vibration period in the acceleration waveform is longer than a predetermined length or when the non-vibration period is shorter than a predetermined length. This allows the system to accurately determine whether the detected vibration is an earthquake or noise by detecting that the vibration period is longer than a predetermined length or that the non-vibration period (the period when vibration has stopped) is shorter than a predetermined length, in order to detect the almost complete absence of vibration cessation that typically appears in acceleration waveforms indicating an earthquake.

[0011] The seismic sensor of the fifth invention is the seismic sensor of the first or second invention, wherein the feature point extraction unit extracts as a feature point that the acceleration waveform contains a proportion of non-periodic movement that is greater than or equal to a predetermined value. This allows accurate determination of whether the detected vibration is an earthquake or noise by detecting whether the proportion of non-periodic motion that appears characteristically in the acceleration waveform indicating an earthquake is equal to or greater than a predetermined value.

[0012] The seismic sensor of the sixth invention is a seismic sensor of the first or second invention, wherein the earthquake determination unit determines that the vibration is an earthquake if the total value of the scores of the feature points calculated by the score calculation unit is greater than or equal to a predetermined threshold value. This allows the system to determine that the detected vibration is an earthquake when the sum of the scores of multiple feature points is equal to or greater than a predetermined threshold, thereby making it possible to comprehensively determine whether an earthquake is occurring based on the multiple feature points contained in the acceleration waveform.

[0013] The seismic sensor of the seventh invention is the seismic sensor of the sixth invention, wherein the earthquake determination unit determines that the vibration is noise if the total value of the scores of the feature points calculated by the score calculation unit is less than a predetermined threshold value. This allows for a comprehensive earthquake assessment to be performed based on the multiple feature points contained in the acceleration waveform by determining that the detected vibration is noise rather than an earthquake if the sum of the scores of multiple feature points is less than a predetermined threshold value.

[0014] The seismic sensor of the eighth invention is the seismic sensor of the seventh invention, in which the earthquake judgment unit quantifies the characteristic points of the acceleration waveform when the vibration is an earthquake, assigns a full score to the representative value of the acceleration waveform of known earthquakes, and subtracts points as the vibration deviates from the representative value, thereby calculating the total score of the characteristic points. This allows, for example, setting the threshold to 0, and if the sum of the scores of multiple feature points is positive, the detected vibration can be determined to be an earthquake, and if the sum is negative, the detected vibration can be determined to be noise.

[0015] The seismic sensor of the ninth invention is the seismic sensor of the eighth invention, in which the earthquake judgment unit increases the deduction rate and judges the vibration to be noise if the vibration deviates from the representative value for a specific parameter among the parameters of the characteristic points.

[0016] As a result, if the characteristics of the acceleration waveform of the detected vibration are significantly different from the representative values ​​of specific parameters that appear in earthquakes, the system determines that the detected vibration is likely to be noise rather than an earthquake, and calculates a score with a larger deduction rate, thereby avoiding incorrectly determining that it is an earthquake even if other parameters have characteristics similar to an earthquake.

[0017] The seismic sensor according to a tenth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising a low-pass filter that cuts high-frequency components above a predetermined frequency of the acceleration acquired by the acceleration acquisition unit. The acceleration waveform generation unit generates an acceleration waveform using the acceleration processed by the low-pass filter. This allows the low-pass filter to cut out high-frequency components that are characteristic of noise, thereby generating an acceleration waveform that makes it easier to detect earthquake characteristics, making it possible to perform earthquake judgment.

[0018] The seismic sensor according to an eleventh aspect of the present invention is the seismic sensor according to the tenth aspect of the present invention, wherein the low-pass filter has a transfer function of a first-order lag system. This means that, for example, in the case of a seismic sensor installed in energy measuring equipment such as gas or electricity, it is possible to cut out vibrations that occur during operation of the energy measuring equipment, generate an acceleration waveform that makes it easier to determine whether an earthquake has occurred, and perform earthquake determination with high real-time accuracy.

[0019] The seismic sensor according to a twelfth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising a frequency detection unit that detects the frequency of the acceleration waveform generated in the acceleration waveform generation unit. This makes it possible to use the frequencies detected from the acceleration waveform to perform earthquake determination, offset adjustment, etc.

[0020] The seismic sensor according to a thirteenth aspect of the present invention is the seismic sensor according to the twelfth aspect of the present invention, wherein the earthquake determination unit determines whether or not the vibration is an earthquake based on the frequency detected by the frequency detection unit. This makes it possible to perform earthquake determination by using the frequency detected from the acceleration waveform to determine whether or not the vibration is an earthquake.

[0021] The seismic sensor of the 14th invention is a seismic sensor of the first or second invention, and further comprises an earthquake magnitude calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake is of a predetermined seismic intensity or greater. This allows for, for example, if the magnitude of the earthquake is judged to be upper 5 or higher on the seismic intensity scale, there is a risk of fire or gas leaks, and a shut-off signal can be output to stop the supply of energy such as electricity or gas, thereby improving the safety of users.

[0022] The seismic sensor of the 15th invention is a seismic sensor of the first or second invention, and further includes an activation determination unit that calculates the vibration intensity from the results acquired by the acceleration acquisition unit, and when the vibration intensity is equal to or greater than a predetermined magnitude, transitions from a power saving mode to a measurement mode that consumes more power than the power saving mode. This allows the device to switch to a measurement mode that performs earthquake detection processing using the vibration acceleration waveform only when the strength of the detected vibration is equal to or greater than a predetermined magnitude (e.g., equivalent to a seismic intensity of 4), thereby enabling highly accurate earthquake detection while reducing power consumption.

[0023] The seismic sensor of the 16th invention is a seismic sensor of the first or second invention, further comprising an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred. This allows, for example, when an earthquake occurs, the output unit to output a cutoff signal to stop the supply of energy such as electricity or gas, or a warning signal to warn of danger.

[0024] An earthquake detection method according to a seventeenth aspect of the present invention includes an acceleration acquisition step, an acceleration waveform generation step, a feature point extraction step, a score calculation step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the acceleration waveform generation step, an acceleration waveform is generated that indicates the relationship between the acceleration measured in the acceleration acquisition step and elapsed time. In the feature point extraction step, feature points that appear as characteristics of an earthquake are extracted from the acceleration waveform generated in the acceleration waveform generation step. In the score calculation step, scores are calculated for the feature points extracted in the feature point extraction step. In the earthquake determination step, it is determined whether the vibrations are an earthquake based on the total score of the multiple feature points calculated in the score calculation step.

[0025] Here, a seismic sensor uses an acceleration waveform formed based on the acceleration of the detected vibration to determine whether the vibration is an earthquake or not, and determines whether the detected vibration is an earthquake or not based on the score of the feature points calculated by extracting feature points that appear as characteristics of an earthquake in the acceleration waveform. Here, the characteristic points that appear in the acceleration waveform as the characteristics of an earthquake include, for example, low-frequency vibrations and non-linear motions contained in the acceleration waveform, almost no non-vibration periods (periods when vibrations are stopped), and non-periodic motions that are equal to or greater than a predetermined rate.

[0026] This allows for the extraction of characteristic points that appear in earthquake vibrations from the acceleration waveform of the detected vibrations, and for the determination of whether the detected vibrations are an earthquake or noise based on the total score of those characteristic points, thereby enabling earthquake determination to be performed by combining various characteristic points that appear in the acceleration waveform of the earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0027] An earthquake detection program according to an eighteenth aspect of the present invention causes a computer to execute an earthquake detection method including an acceleration acquisition step, an acceleration waveform generation step, a feature point extraction step, a score calculation step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the acceleration waveform generation step, an acceleration waveform is generated that indicates the relationship between the acceleration measured in the acceleration acquisition step and elapsed time. In the feature point extraction step, feature points that appear as characteristics of an earthquake are extracted from the acceleration waveform generated in the acceleration waveform generation step. In the score calculation step, scores are calculated for the feature points extracted in the feature point extraction step. In the earthquake determination step, it is determined whether the vibrations are an earthquake based on the total score of the multiple feature points calculated in the score calculation step.

[0028] Here, a seismic sensor uses an acceleration waveform formed based on the acceleration of the detected vibration to determine whether the vibration is an earthquake or not, and determines whether the detected vibration is an earthquake or not based on the score of the feature points calculated by extracting feature points that appear as characteristics of an earthquake in the acceleration waveform. Here, the characteristic points that appear in the acceleration waveform as the characteristics of an earthquake include, for example, low-frequency vibrations and non-linear motions contained in the acceleration waveform, almost no non-vibration periods (periods when vibrations are stopped), and non-periodic motions that are equal to or greater than a predetermined rate.

[0029] This allows for the extraction of characteristic points that appear in earthquake vibrations from the acceleration waveform of the detected vibrations, and for the determination of whether the detected vibrations are an earthquake or noise based on the total score of those characteristic points, thereby enabling earthquake determination to be performed by combining various characteristic points that appear in the acceleration waveform of the earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise. [Effects of the Invention]

[0030] The seismic sensor according to the present invention can accurately determine whether the detected vibration is an earthquake or noise. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a control block diagram showing the configuration of a seismic sensor according to an embodiment of the present invention. [Figure 2] Functional block diagram generated within the seismic sensor in Figure 1. [Figure 3] (a) is a graph showing the relationship between the acceleration of the detected vibration and the elapsed time (acceleration waveform). (b) is a graph showing the relationship between the frequency and spectrum obtained by FFT (Fast Fourier Transform) analysis of the acceleration waveform in (a). [Figure 4] (a) is a graph showing the acceleration waveform after high-frequency components have been removed using a low-pass filter from the acceleration waveform in Figure 4(a). (b) is a graph showing the relationship between frequency and spectrum obtained by FFT analysis of the acceleration waveform in (a). [Figure 5] 3 is a flowchart showing the process flow of an earthquake determination method carried out by the seismic sensor of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0032] A seismic sensor 10 according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. In the present embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present invention, and they are not intended to limit the subject matter described in the claims.

[0033] (1) Configuration of the seismic sensor 10 As shown in FIG. 1, the seismic sensor 10 according to this embodiment includes an acceleration sensor 11, a controller 12, and a memory 13.

[0034] The acceleration sensor 11 is, for example, an acceleration sensor using a piezoelectric element or an acceleration sensor that detects electrostatic capacitance between electrodes. The acceleration measured (also called “sampling”) by the acceleration sensor 11 is output to the controller 12. The controller 12 is, for example, a general-purpose integrated circuit that acquires the acceleration measured by the acceleration sensor 11 at a predetermined period, detects the occurrence of an earthquake based on the acquired acceleration, and calculates an index value indicating the magnitude of the earthquake.

[0035] Also, the controller 12 operates in different modes, active mode or sleep mode, depending on the situation. The sleep mode is a mode in which the controller 12 operates with limited functions, such as stopping the execution of instructions while accepting interrupts, stopping the supply of clocks, etc. In this sleep mode, power consumption can be reduced more than in the active mode.

[0036] The active mode is a mode in which a process is performed to determine whether the detected vibration is an earthquake or noise, and an index value indicating the magnitude of the earthquake is calculated. The function blocks (see FIG. 2) generated when the CPU in the seismic sensor 10 reads the earthquake detection program stored in the memory 13 will be described in detail later. The memory 13 is a temporary storage means such as a RAM (Random Access Memory) or a non-volatile memory such as an EPROM (Erasable Programmable Read Only Memory), and stores, for example, the acceleration measured by the acceleration sensor 11 and threshold values ​​used for earthquake determination.

[0037] The memory 13 may be a memory built into the acceleration sensor 11 or the controller 12 . The output unit 14 is, for example, an output terminal included in the controller 12, and when the controller 12 determines that, for example, an earthquake has occurred, information indicating the occurrence and scale of the earthquake is output to another device via the output unit 14. Furthermore, when an earthquake of a predetermined scale or greater is detected, the output unit 14 outputs, for example, a cutoff signal to an external device to stop the supply of energy such as electricity or gas.

[0038] (2) Functional block of seismic sensor 10 As shown in Figure 2, the seismic sensor 10 includes an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a vibration intensity classification / activation determination unit 23, a frequency detection unit 24, a feature point extraction unit 25a, a score calculation unit 25b, an earthquake determination unit 26, an earthquake magnitude calculation unit 27, an output control unit 28, an offset adjustment unit 29, and a memory unit 30.

[0039] These functional blocks shown in FIG. 2 are configured by the controller 12 receiving acceleration data obtained from the acceleration sensor 11 and reading a program stored in the memory 13. The acceleration acquiring unit 21 acquires measurement data of acceleration measured at a predetermined period by the acceleration sensor 11. Note that the acceleration acquiring unit 21 normally acquires measurement data of acceleration measured repeatedly at a relatively low speed (i.e., at a relatively large measurement period).

[0040] When performing such low-speed acceleration sampling, the controller 12 basically operates in a sleep mode (standby state or power-saving mode) with low power consumption. In the standby state, the acceleration sensor 11 is in an operating state where it samples at a low speed, so the controller 12 operates in a sleep mode with limited functionality, thereby reducing power consumption.

[0041] Furthermore, when the acceleration acquisition unit 21 acquires vibrations greater than a threshold value preset in the storage unit 30, the acceleration sensor 11 repeats measuring the acceleration at a higher speed (i.e., at a relatively short cycle) than during low-speed sampling. During such high-speed sampling, the controller 12 operates in a sleep mode or an active mode. When the earthquake determination unit 26 (described later) and the like execute processing, the controller 12 operates in active mode (measurement mode). The transition from the power saving mode to the measurement mode is called the activation of the seismic sensor 10.

[0042] The measurement mode is an operating state in which high-speed sampling is performed, so the controller 12 may operate in a sleep mode with limited functionality, or in an active mode with maximum computing power. In the measurement mode, the sampling period is shortened and the controller 12 switches from the sleep mode to the active mode, resulting in higher power consumption than in the power-saving mode.

[0043] The acceleration waveform generating unit 22 generates an acceleration waveform indicating the relationship between the acceleration measured by the acceleration acquiring unit 21 and elapsed time (see FIG. 3(a)).The acceleration waveform generating unit 22 then generates an acceleration waveform using acceleration that has been processed by a low-pass filter that cuts out high-frequency components of the acceleration acquired by the acceleration acquiring unit 21 that are equal to or higher than a predetermined frequency (for example, 25 Hz) (see FIG. 4(a)).

[0044] Here, the low-pass filter of the first-order delay system is expressed by the following relational expression, where y is the acceleration after filtering, x is the acceleration, fc is the cutoff frequency, and fs is the sampling frequency.

[0045]

number

[0046] Therefore, in the earthquake determination process described later, earthquake determination can be performed using an acceleration waveform from which high frequency components characteristic of noise have been removed. The low-pass filter used by the acceleration waveform generating unit 22 has, for example, a transfer function of a first-order lag system. This makes it possible to cut out vibrations that occur during the operation of measuring equipment etc. to which the seismic sensor 10 is attached, thereby generating an acceleration waveform that makes it easier to determine whether an earthquake is occurring, and also makes it possible to perform earthquake determination with high real-time accuracy.

[0047] The vibration intensity discrimination and activation determination unit 23 is a function on the acceleration sensor 11 side, which compares the acceleration value acquired by the acceleration acquisition unit 21 with the activation threshold value stored in the memory unit 30, and if the acceleration value exceeds the activation threshold value, transitions from power saving mode to measurement mode (activates the seismic sensor 10). In addition, the vibration intensity discrimination / activation determination unit 23 calculates the vibration intensity from the measurement results of the acceleration acquisition unit 21, and if the vibration intensity is equal to or greater than a predetermined magnitude, transitions from the power saving mode to the measurement mode, which consumes more power than the power saving mode (activates the controller 12).

[0048] Here, the vibration intensity classification process performed by the vibration intensity classification / activation determination unit 23 is performed by filtering the acceleration value acquired by the acceleration acquisition unit 21. At this time, the filtered acceleration is stored in the storage unit 30. The frequency detection section 24 detects the frequency of the acceleration waveform generated by the acceleration waveform generation section 22 using, for example, a zero crossing method.

[0049] The zero-crossing method is a method that detects the time between the point where a waveform crosses zero (or a hysteresis value set near zero) and the next point where it crosses zero (or a hysteresis value set near zero) as one cycle (frequency). Compared to the peak method, which detects the time between one peak in a waveform and the next peak as one cycle, the zero-crossing method makes it more difficult to detect minute vibrations, but it eliminates the effects of noise near zero acceleration (within the hysteresis range) and can detect frequencies with high accuracy without being affected by minute vibration noise around the peak value.

[0050] The feature point extracting unit 25a extracts feature points that appear as earthquake characteristics from the acceleration waveform generated by the acceleration waveform generating unit 22. Here, the characteristic points that emerge as characteristics of an earthquake include, for example, low-frequency vibrations and non-linear motions contained in the acceleration waveform, almost no non-vibration periods (periods when vibrations are stopped), and non-periodic motions that are greater than a certain percentage.

[0051] Specifically, the feature point extracting unit 25a extracts, as a feature point, that the acceleration waveform contains a low-frequency vibration or a non-linear motion portion. Also, the feature point extracting unit 25a extracts, as a feature point, that the acceleration waveform has almost no non-vibration period (period of no vibration) (the vibration period is equal to or longer than a predetermined length, or the non-vibration period is equal to or shorter than a predetermined length), or that the proportion of non-periodic motion is equal to or greater than a predetermined value.

[0052] The score calculation unit 25b calculates the scores of the feature points extracted by the feature point extraction unit 25a. The earthquake determination unit 26 determines whether or not the detected vibration is an earthquake based on the total value of the scores of the plurality of feature points calculated by the score calculation unit 25b. Specifically, if the sum of the scores of the feature points calculated by the score calculation unit 25b is equal to or greater than a predetermined threshold, the earthquake determination unit 26 determines that the detected vibration is an earthquake. On the other hand, if the sum of the scores of the feature points calculated by the score calculation unit 25b is less than the predetermined threshold, the earthquake determination unit 26 determines that the detected vibration is noise.

[0053] Furthermore, the earthquake determination unit 26 quantifies the characteristic points of the acceleration waveform when the vibration is an earthquake, assigns a full score to the representative value of the acceleration waveform of known earthquakes, and subtracts points as the vibration deviates from the representative value, thereby calculating the total score of the characteristic points. As a result, if the total score of multiple feature points is positive, the detected vibration can be determined to be an earthquake, and if the total score is negative, the detected vibration can be determined to be noise.

[0054] Furthermore, when the vibration deviates from the representative value for a specific parameter (algorithm) among the parameters (algorithms) of the characteristic point, the earthquake determination unit 26 increases the deduction rate and determines the vibration to be noise. As a result, if the acceleration waveform of the detected vibration is significantly different from the representative value of a specific parameter that appears in earthquakes (for example, the median value of all earthquakes), it is possible to determine that the detected vibration is likely to be noise rather than an earthquake, and to calculate a score with a larger deduction rate.As for other parameters, it is possible to avoid incorrectly determining that it is an earthquake even if they have characteristics similar to those of an earthquake.

[0055] When the earthquake determination unit 26 determines that an earthquake has occurred, the earthquake magnitude calculation unit 27 determines whether the earthquake has a seismic intensity of at least a predetermined level. Furthermore, after the earthquake magnitude calculation unit 27 determines that the detected vibration is an earthquake and starts calculating an index indicating the magnitude of the earthquake, if an acceleration waveform that can be considered to be an impact is detected, the earthquake magnitude calculation unit 27 excludes the acceleration waveform and calculates the magnitude of the earthquake.

[0056] At this time, the frequency detection unit 24 detects a frequency that is used to determine whether the detected acceleration waveform can be regarded as an impact or not, by a peak method. The output control unit 28 controls the output of a signal from the output unit 14, which outputs a predetermined signal, depending on whether the magnitude of the earthquake calculated by the earthquake magnitude calculation unit 27 is equal to or greater than a predetermined seismic intensity.

[0057] Here, the predetermined signal output from the output unit 14 includes, for example, a shutoff signal sent to an external device such as an electricity supply device or a gas supply device in order to stop the supply of energy such as electricity or gas. When earthquake determination unit 26 determines that the vibration detected by acceleration acquisition unit 21 is noise, offset adjustment unit 29 adjusts the offset amount of the acceleration waveform according to the magnitude of the noise. Then, offset adjustment unit 29 adjusts the offset amount of the acceleration waveform according to the determination result of earthquake determination unit 26 made based on the acceleration waveform.

[0058] The offset adjustment performed by the offset adjuster 29 detects noise components contained in the measured acceleration as offset components, such as the amount of change in the measurement value that occurs with changes over time in the seismic sensor 10, the amount of change in the measurement value that occurs with temperature changes, and the amount of change in the measurement value that occurs when the orientation of the installed seismic sensor 10 tilts for some reason and the direction of gravitational acceleration relative to the seismic sensor 10 changes. Specifically, the offset adjuster 29 calculates, for example, the median of the maximum and minimum values ​​of the acceleration determined to be noise, or the average value of the acceleration, as the offset component. The memory unit 30 stores, for example, acceleration data acquired by the acceleration acquisition unit 21, or acceleration data after filtering processing, the judgment results of the earthquake judgment unit 26, offset component data used in the offset adjustment unit 29, etc.

[0059] <Earthquake detection method> The earthquake detection method using the seismic sensor 10 of this embodiment will be described below with reference to the flowchart shown in FIG.

[0060] That is, in step S11, the acceleration acquisition unit 21 of the seismic sensor 10 acquires the acceleration measured by the acceleration sensor 11. Next, in step S12, the acceleration waveform generating unit 22 uses a first-order lag low-pass filter to cut high frequency components having frequencies of, for example, 25 Hz or higher and pass frequencies below 25 Hz.

[0061] Next, in step S13, the acceleration waveform generating unit 22 generates an acceleration waveform using the acceleration that has been subjected to high-cut (low-pass) processing in step S12. Next, in step S14, the feature point extraction unit 25a measures the frequency distribution of angles formed by successive acceleration vectors on a horizontal plane to detect whether or not the acceleration waveform contains low-frequency components, and the score calculation unit 25b converts this angle frequency distribution into a score.

[0062] At this time, the score calculation unit 25b sets the threshold value of the detected frequency to, for example, 10 Hz, and if there are many frequency components higher than the threshold 10 Hz, it sets "-1", and if there are many frequency components lower than the threshold 10 Hz, it sets "+1".The score calculation unit 25b then determines that the more frequently there are high frequency components that differ from 10 Hz, the more likely it is that the signal is not an earthquake, and increases the negative score.

[0063] Here, the frequency distribution of angles may be scored using the measured angles as a threshold value. As a result, by increasing the negative value as the detected frequency has more high-frequency components that are significantly different from the threshold value of 10 Hz, if there are few low-frequency components that are characteristic of earthquakes and many high-frequency components that are characteristic of daily vibrations, the earthquake determination unit 26 can determine that there is no earthquake without being affected by the scores of other parameters (algorithms).

[0064] Next, in step S15, the feature point extraction unit 25a measures periods during which the displacement does not vibrate significantly (non-vibration periods) to detect whether the acceleration waveform includes non-vibration periods (vibration stop periods), and the score calculation unit 25b converts the proportion of these non-vibration periods into a score. At this time, the score calculation unit 25b sets "-1" if the ratio of the detected non-vibration period (vibration stop period) is greater than the ratio of the vibration period to the entire period in which vibration was detected, and sets "+1" if it is smaller than the ratio of the vibration period.The score calculation unit 25b determines that the greater the ratio of the non-vibration period (vibration stop period), the lower the possibility that the earthquake has almost no vibration stop period, and increases the negative score.

[0065] By increasing the negative value as the proportion of non-vibration periods in the detected vibration increases, if the proportion of non-vibration periods (periods where vibration is stopped), which are characteristic of earthquakes, is small and the proportion of non-vibration periods (periods where vibration is stopped), which are characteristic of daily vibrations, is large, the earthquake determination unit 26 can determine that there is no earthquake, without being influenced by the scores of other parameters (algorithms).

[0066] Next, in step S16, the feature point extraction unit 25a measures the frequency distribution of the direction angle of acceleration on the horizontal plane (non-linear movement) to detect whether or not non-linear movement is included in the acceleration waveform, and the score calculation unit 25b converts the frequency of this non-linear movement into a score. At this time, the score calculation unit 25b sets "-1" when the frequency of the detected non-linear movement is smaller than a predetermined threshold, and sets "+1" when it is larger than the predetermined threshold. The score calculation unit 25b determines that the possibility that the non-linear movement is not an earthquake decreases as the frequency of the non-linear movement decreases, and increases the negative score.

[0067] As a result, by increasing the negative value as the frequency of non-linear movement in the detected vibration decreases, if there is little non-linear movement that is characteristic of earthquakes and a lot of non-linear movement that is characteristic of daily vibrations, the earthquake determination unit 26 can determine that there is no earthquake without being influenced by the scores of other parameters (algorithms). Next, in step S17, the feature point extraction unit 25a measures the frequency distribution of periods (non-periodic movement) to detect whether or not the acceleration waveform contains non-periodic movement, and the score calculation unit 25b converts the frequency of this non-periodic movement into a score.

[0068] At this time, the score calculation unit 25b sets "-1" if the frequency of the detected non-periodic movement is smaller than a predetermined threshold, and sets "+1" if it is larger than the predetermined threshold. The score calculation unit 25b determines that the smaller the frequency of the non-periodic movement, the more likely it is not an earthquake, and increases the negative score. As a result, by increasing the negative value as the frequency of non-periodic periods in the detected vibration decreases, if there is little non-periodic movement that is characteristic of earthquakes and much non-periodic movement that is characteristic of daily vibrations, the earthquake determination unit 26 can determine that there is no earthquake without being influenced by the scores of other parameters (algorithms).

[0069] Next, in step S18, the scoring process for each parameter (algorithm) in steps S14 to S17 is completed, and it is determined whether or not to end the earthquake determination process. If the earthquake determination process is to be ended, the process proceeds to step S19, and if the earthquake determination process is not to be ended, the process returns to step S11. Next, in step S19, the results of the scoring process for each parameter (algorithm) in steps S14 to S17 are tallied and converted into a score.

[0070] Here, in steps S14 to S17, a score of "-1" or "+1" is assigned, and in particular, if the characteristics of the acceleration waveform are highly unlikely to be an earthquake, a score with a large negative value is assigned to that parameter (algorithm). Next, in step S20, the earthquake determination unit 26 determines whether the total score is equal to or greater than 0. If the specific total is equal to or greater than 0, the process proceeds to step S21, and if it is less than 0, the process proceeds to step S22.

[0071] Next, in step S21, since it is determined in step S20 that the total score is equal to or greater than "0", the earthquake determination unit 26 determines that the detected vibration is an earthquake and ends the process. On the other hand, in step S22, since it is determined in step S20 that the total score is less than "0", the earthquake determination unit 26 determines that the detected vibration is not an earthquake (is noise) and ends the process.

[0072] <Major features> The seismic sensor 10 of this embodiment includes an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a feature point extraction unit 25a, a score calculation unit 25b, and an earthquake determination unit 26. The acceleration acquisition unit 21 detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation unit 22 generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition unit 21 and elapsed time. The feature point extraction unit 25a extracts feature points that appear as characteristics of an earthquake from the acceleration waveform generated by the acceleration waveform generation unit 22. The score calculation unit 25b calculates scores for the feature points extracted by the feature point extraction unit 25a. The earthquake determination unit 26 determines whether the vibrations are an earthquake based on the total score of the multiple feature points calculated by the score calculation unit 25b.

[0073] This allows for the extraction of characteristic points that appear in earthquake vibrations from the acceleration waveform of the detected vibrations, and for the determination of whether the detected vibrations are an earthquake or noise based on the total score of those characteristic points, thereby enabling earthquake determination to be performed by combining various characteristic points that appear in the acceleration waveform of the earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0074] [Other embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0075] (A) In the above embodiment, the present invention has been described as being implemented as a seismic sensor and an earthquake detection method, but the present invention is not limited to this.

[0076] For example, the present invention may be realized as an earthquake detection program that causes a computer to execute the earthquake detection method using the seismic sensor described above. This earthquake detection program is stored in a memory (storage unit) installed in the seismic sensor, and the CPU reads the earthquake detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU reads the earthquake detection program and executes the acceleration acquisition step, acceleration waveform generation step, feature point extraction step, score calculation step, and earthquake determination step described above, thereby achieving the same effects as those described above. The present invention may also be realized as a recording medium storing an earthquake detection program for a seismic sensor.

[0077] (B) In the above embodiment, an example was given in which earthquake detection was performed on the generated acceleration waveform using the frequency of low-frequency vibration, the ratio of non-vibration periods, the frequency of non-linear motion, and the frequency of non-periodic motion as parameters (algorithms). However, the present invention is not limited to this. For example, earthquake determination may be performed by combining parameters (algorithms) other than those described above. Alternatively, earthquake determination may be performed by replacing the above parameters (algorithms) with other parameters (algorithms).

[0078] (C) In the above embodiment, an example has been described in which an earthquake is determined to have occurred when the total score is equal to or greater than "0," and an earthquake is determined not to have occurred when the total score is less than "0." However, the present invention is not limited to this. For example, the score calculation unit may add points for each parameter (algorithm), and the earthquake determination unit may determine that there is an earthquake if the sum of the added points is equal to or greater than a predetermined threshold, and determine that there is noise if the sum is less than the threshold.

[0079] (D) In the above embodiment, when scoring the characteristic points of known earthquakes in each algorithm, an example was explained in which the "median" is used as the representative value of all earthquakes, and the further away from the representative value the noise characteristic side, the more points are deducted (points below 0 are negative points). However, the present invention is not limited to this. For example, when scoring each algorithm, a value other than the median (such as an average value) may be used as a representative value of the data for all earthquakes to score each parameter (algorithm) of the detected vibrations.

[0080] (E) In the above embodiment, when scoring the characteristic points of known earthquakes in each algorithm, an example was explained in which the "median" is used as the representative value of all earthquakes, and the further away from the representative value the noise characteristic side, the more points are deducted (points below 0 are negative points). However, the present invention is not limited to this. For example, in order to adjust the deduction rate or the maximum score, the deduction rate may be increased the clearer the distinction between earthquakes and noise is in each algorithm, or weighting may be applied when scoring (the closer the characteristics of an earthquake, the greater the added score, and the closer the characteristics of noise, the greater the deduction) so that the maximum score is increased for an algorithm with a higher earthquake / noise discrimination rate compared to other algorithms.

[0081] (F) In the above embodiment, a configuration including a low-pass filter that removes high-frequency components having a predetermined frequency or higher from the generated acceleration waveform has been described as an example. However, the present invention is not limited to this. For example, the low-pass filter may not be provided.

[0082] (G) In the above embodiment, an example was given in which high frequency components were cut using a low-pass filter with a threshold value of 25 Hz, but the present invention is not limited to this. For example, the threshold for cutting high frequency components may be a value greater than 25 Hz or a value less than 25 Hz.

[0083] <Additional Notes> The seismic sensor according to the first invention is an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an acceleration waveform generating unit that generates an acceleration waveform indicating a relationship between the acceleration measured by the acceleration acquiring unit and elapsed time; a feature point extraction unit that extracts feature points that appear as characteristics of an earthquake from the acceleration waveform generated by the acceleration waveform generation unit; a score calculation unit that calculates scores of the feature points extracted by the feature point extraction unit; an earthquake determination unit that determines whether the vibration is an earthquake based on the total score of the plurality of feature points calculated by the score calculation unit; It is equipped with:

[0084] The seismic sensor according to the second invention is the seismic sensor according to the first invention, The feature point extraction unit extracts, as a feature point, the inclusion of low frequency vibration in the acceleration waveform. The seismic sensor according to the third invention is the seismic sensor according to the first or second invention, The feature point extraction unit extracts, as a feature point, the inclusion of non-linear motion in the acceleration waveform.

[0085] A seismic sensor according to a fourth aspect of the present invention is a seismic sensor according to any one of the first to third aspects of the present invention, The feature point extracting unit extracts, as a feature point, a vibration period having a predetermined length or more or a non-vibration period having a predetermined length or less in the acceleration waveform. A seismic sensor according to a fifth aspect of the present invention is a seismic sensor according to any one of the first to fourth aspects of the present invention, The feature point extraction unit extracts, as a feature point, a non-periodic movement rate equal to or greater than a predetermined value in the acceleration waveform.

[0086] A seismic sensor according to a sixth aspect of the present invention is a seismic sensor according to any one of the first to fifth aspects of the present invention, The earthquake determination unit determines that the vibration is an earthquake when the total value of the scores of the feature points calculated by the score calculation unit is equal to or greater than a predetermined threshold value. A seismic sensor according to a seventh aspect of the present invention is the seismic sensor according to the sixth aspect of the present invention, The earthquake determination unit determines the vibration to be noise when the sum of the scores of the feature points calculated by the score calculation unit is less than a predetermined threshold value.

[0087] The seismic sensor according to an eighth aspect of the present invention is the seismic sensor according to the seventh aspect of the present invention, The earthquake determination unit quantifies the characteristic points of the acceleration waveform when the vibration is an earthquake, assigns a full score to the representative value of the acceleration waveform of known earthquakes, and subtracts points as the vibration deviates from the representative value, thereby calculating the total score of the characteristic points. A seismic sensor according to a ninth aspect of the present invention is the seismic sensor according to the eighth aspect of the present invention, When a vibration deviates from the representative value for a specific parameter among the parameters of the characteristic points, the earthquake determination unit increases the deduction rate and determines the vibration to be noise.

[0088] A seismic sensor according to a tenth aspect of the present invention is a seismic sensor according to any one of the first to ninth aspects of the present invention, a low-pass filter that cuts high-frequency components of the acceleration acquired by the acceleration acquisition unit that are equal to or higher than a predetermined frequency; The acceleration waveform generating unit generates an acceleration waveform using the acceleration processed by the low-pass filter.

[0089] A seismic sensor according to an eleventh aspect of the present invention is the seismic sensor according to the tenth aspect of the present invention, The low-pass filter has a transfer function of a first-order lag system. A seismic sensor according to a twelfth aspect of the present invention is the seismic sensor according to any one of the first to eleventh aspects of the present invention, The acceleration waveform generating unit further includes a frequency detecting unit that detects the frequency of the acceleration waveform generated by the acceleration waveform generating unit.

[0090] A seismic sensor according to a thirteenth aspect of the present invention is the seismic sensor according to the twelfth aspect of the present invention, The earthquake determination unit determines whether the vibration is an earthquake based on the frequency detected by the frequency detection unit. A seismic sensor according to a fourteenth aspect of the present invention is the seismic sensor according to any one of the first to thirteenth aspects of the present invention, The earthquake detection unit further includes an earthquake magnitude calculation unit that determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity when the earthquake determination unit determines that an earthquake has occurred.

[0091] A seismic sensor according to a fifteenth aspect of the present invention is a seismic sensor according to any one of the first to fourteenth aspects of the present invention, The device further includes an activation determination unit that calculates the vibration intensity from the results acquired by the acceleration acquisition unit, and when the vibration intensity is equal to or greater than a predetermined magnitude, transitions from a power saving mode to a measurement mode that consumes more power than the power saving mode.

[0092] A seismic sensor according to a sixteenth aspect of the present invention is a seismic sensor according to any one of the first to fifteenth aspects of the present invention, The earthquake detection unit further includes an output control unit that outputs the predetermined signal when it is determined that an earthquake has occurred. [Industrial Applicability]

[0093] The seismic sensor of the present invention has the effect of being able to accurately determine whether a detected vibration is an earthquake or noise, and is therefore widely applicable to sensors that detect various types of vibration. [Explanation of symbols]

[0094] 10 Seismic Sensor 11 Acceleration sensor 12 Controllers 13. Memory 14 Output section 21 Acceleration acquisition section 22 Acceleration waveform generator 23 Vibration intensity classification / startup determination section 24 Frequency detection section 25a Feature point extraction unit 25b Score calculation section 26 Earthquake Determination Department 27 Earthquake scale calculation department 28 Output control section 29 Offset adjustment section 30 Storage section

Claims

1. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an acceleration waveform generating unit that generates an acceleration waveform indicating a relationship between the acceleration measured by the acceleration acquiring unit and elapsed time; a feature point extraction unit that extracts feature points that appear as characteristics of an earthquake from the acceleration waveform generated by the acceleration waveform generation unit; a score calculation unit that calculates scores of the feature points extracted by the feature point extraction unit; an earthquake determination unit that determines whether the vibration is an earthquake based on the total score of the plurality of feature points calculated by the score calculation unit; A seismic sensor equipped with:

2. the feature point extraction unit extracts, as a feature point, that the acceleration waveform contains low-frequency vibrations; The seismic sensor according to claim 1 .

3. the feature point extraction unit extracts, as a feature point, that the acceleration waveform includes non-linear motion; The seismic sensor according to claim 1 or 2.

4. the feature point extraction unit extracts, as a feature point, a vibration period having a predetermined length or more, or a non-vibration period having a predetermined length or less, in the acceleration waveform; The seismic sensor according to claim 1 or 2.

5. the feature point extraction unit extracts, as a feature point, a point in which the acceleration waveform contains a ratio of non-periodic movement equal to or greater than a predetermined value; The seismic sensor according to claim 1 or 2.

6. the earthquake determination unit determines that the vibration is an earthquake when the total value of the scores of the feature points calculated by the score calculation unit is equal to or greater than a predetermined threshold value. The seismic sensor according to claim 1 or 2.

7. the earthquake determination unit determines the vibration to be noise when the sum of the scores of the feature points calculated by the score calculation unit is less than a predetermined threshold value; The seismic sensor according to claim 6.

8. The earthquake determination unit quantifies the characteristic points of the acceleration waveform when the vibration is an earthquake, assigns a full score to a representative value of the acceleration waveform of known earthquakes, and subtracts points as the vibration deviates from the representative value, thereby calculating a total score of the characteristic points. The seismic sensor according to claim 7.

9. When the vibration deviates from the representative value for a specific parameter among the parameters of the feature points, the earthquake determination unit increases the deduction rate and determines the vibration to be noise. The seismic sensor according to claim 8.

10. a low-pass filter that cuts high-frequency components of the acceleration acquired by the acceleration acquisition unit that are equal to or higher than a predetermined frequency; the acceleration waveform generation unit generates an acceleration waveform using the acceleration processed by the low-pass filter. The seismic sensor according to claim 1 or 2.

11. The low-pass filter has a transfer function of a first-order lag system. The seismic sensor according to claim 10.

12. The acceleration waveform generating unit may further include a frequency detecting unit that detects a frequency of the acceleration waveform generated by the acceleration waveform generating unit. The seismic sensor according to claim 1 or 2.

13. the earthquake determination unit determines whether the vibration is an earthquake based on the frequency detected by the frequency detection unit. The seismic sensor according to claim 12.

14. The apparatus further includes an earthquake magnitude calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity. The seismic sensor according to claim 1 or 2.

15. The device further includes an activation determination unit that calculates the intensity of the vibration from the result of acquisition by the acceleration acquisition unit, and when the intensity of the vibration is equal to or greater than a predetermined magnitude, transitions from the power saving mode to a measurement mode that consumes more power than the power saving mode. The seismic sensor according to claim 1 or 2.

16. The earthquake determination unit further includes an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred. The seismic sensor according to claim 1 or 2.

17. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an acceleration waveform generating step of generating an acceleration waveform indicating a relationship between the acceleration measured in the acceleration acquiring step and elapsed time; a feature point extraction step of extracting feature points that appear as earthquake characteristics from the acceleration waveform generated by the acceleration waveform generation step; a score calculation step of calculating scores of the feature points extracted in the feature point extraction step; an earthquake determination step of determining whether the vibration is an earthquake based on the total value of the scores of the plurality of feature points calculated in the score calculation step; An earthquake detection method comprising:

18. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an acceleration waveform generating step of generating an acceleration waveform indicating a relationship between the acceleration measured in the acceleration acquiring step and elapsed time; a feature point extraction step of extracting feature points that appear as earthquake characteristics from the acceleration waveform generated by the acceleration waveform generation step; a score calculation step of calculating scores of the feature points extracted in the feature point extraction step; an earthquake determination step of determining whether the vibration is an earthquake based on the total value of the scores of the plurality of feature points calculated in the score calculation step; An earthquake detection program that causes a computer to execute an earthquake detection method comprising:

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