Seismic sensor and earthquake detection method, as well as earthquake detection program

Abstract

To provide a seismic sensor and an earthquake detection method, as well as an earthquake detection program that can remove influence due to temporal tilt generated immediately after occurrence of vibration to accurately perform determination of the vibration.SOLUTION: A seismic sensor 10 comprises: an acceleration acquisition unit 21; an earthquake determination unit 25; an offset adjustment unit 29; a convergence determination unit 29a; and an origin correction necessity determination unit 29b. The offset adjustment unit 29 adjusts an offset amount according to magnitude of vibration after detecting a noise included in the vibration detected by the earthquake determination unit 25. The convergence determination unit 29a determines whether or not the vibration has been converged. The origin correction necessity determination unit 29b determines whether or not origin correction of acceleration is performed according to whether or not the offset amount calculated according to the magnitude of the vibration after detecting the noise is the same degree as the offset amount of the previous time at time when a predetermined period has passed over from a time point when it is determined that the vibration has been converged in the convergence determination unit 29a.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 built into gas meters, power meters, distribution boards, outlets, etc., and are used to output a cut-off signal to cut off the supply of gas, electricity, etc. when they detect earthquake motion above a predetermined value (for example, seismic intensity 5+ or above). For example, Patent Document 1 discloses a seismic sensor that includes an earthquake judgment unit that switches from a power saving mode to a measurement mode that consumes more power when the measured acceleration exceeds a predetermined threshold, and judges the occurrence of an earthquake based on the acceleration measured during the subsequent judgment period, and an index calculation unit that calculates an index value indicating the magnitude of the earthquake in an earthquake processing period following the judgment period when the earthquake judgment unit judges that an earthquake has occurred, and outputs a cut-off signal when the index value during the earthquake processing period is equal to or greater than the threshold, and further includes a continuing earthquake judgment unit that judges the occurrence of an earthquake based on the acceleration measured during the earthquake processing period, and a cut-off judgment unit that prevents the cut-off signal from being output regardless of the index value when the continuing earthquake judgment unit determines that an earthquake has not occurred.

[0003] This seismic sensor can prevent noise from being erroneously determined to be an earthquake and an erroneous output of a shutoff signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6465257 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional seismic sensor has the following problems. In other words, in the seismic sensor disclosed in the above publication, after detecting an earthquake, it is determined that the vibration has converged, and the offset amount is immediately adjusted when the vibration has converged. Therefore, for example, if the detected vibration is a low-frequency vibration, the sensor is temporarily tilted, and the tilt then becomes smaller, it is difficult to maintain high accuracy in the detection by adjusting the offset immediately after the vibration has converged.

[0006] The object of the present invention is to provide a seismic sensor, an earthquake detection method, and an earthquake detection program that are capable of determining vibration with high accuracy by eliminating the effects of temporary tilt that occurs immediately after the occurrence of vibration. [Means for solving the problem]

[0007] The seismic sensor according to the first invention includes an acceleration acquisition unit, an earthquake determination unit, an offset adjustment unit, a convergence determination unit, and an origin correction necessity determination unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The earthquake determination unit determines whether the vibrations are earthquakes or not based on the acceleration acquired by the acceleration acquisition unit. The offset adjustment unit adjusts the offset amount according to the magnitude of the vibrations after detecting noise contained in the vibrations detected by the earthquake determination unit. The convergence determination unit determines whether the vibrations have converged. The origin correction necessity determination unit determines whether to perform origin correction of the accelerations or not depending on whether the offset amount calculated according to the magnitude of the vibrations after the noise is detected is approximately the same as the previous offset amount when a predetermined period of time has elapsed since the convergence determination unit determined that the vibrations have converged.

[0008] Here, in a seismic sensor that determines whether or not a vibration is an earthquake based on the acceleration of the detected vibration, and adjusts the offset amount to eliminate the effects of noise depending on the magnitude of the vibration after the noise is detected, the system detects whether or not the seismic sensor is tilted and determines whether or not to perform an origin correction depending on whether or not the offset amount calculated after a predetermined period of time has elapsed (for example, 5 to 20 seconds has elapsed) from the time it is determined that the vibration has converged is approximately the same as the previous offset amount.

[0009] Here, the previous offset amount to be compared with the newly calculated offset amount based on the magnitude of vibration after noise is detected is the offset amount calculated the previous time vibration was detected, and means, for example, the offset amount stored in the seismic sensor. In addition, examples of vibrations that cause the seismic sensor to return to its original tilt after a predetermined period of time include low-frequency vibrations.

[0010] As a result, if it is determined that the current offset amount is approximately the same as the previous offset amount after a predetermined period of time has passed after the vibrations have subsided (for example, after 5 to 20 seconds have passed), it is presumed that the seismic sensor is almost not tilted, whereas if there is a large difference compared to the previous offset amount, it is presumed that there is a high possibility that the seismic sensor remains tilted. Therefore, after the vibration has subsided, if it continues for a predetermined time or more, the offset amount including origin correction is adjusted in that tilted state, and if the tilt does not continue for the predetermined time, the offset adjustment can be performed using a new offset amount with the tilt returned to its original state. As a result, the influence of a temporary tilt that occurs immediately after the occurrence of vibration is eliminated, and vibration can be determined with high accuracy.

[0011] The seismic sensor of the second invention is the seismic sensor of the first invention, wherein the offset adjustment unit performs offset adjustment using a new offset amount when the offset amount is approximately the same as the previous offset amount. As a result, if it is determined that the current offset amount is approximately the same as the previous offset amount within a specified period of time (e.g., 5 to 20 seconds) after the vibrations have subsided, it is assumed that there is almost no tilt in the seismic sensor, and offset adjustment can be performed using the newly calculated offset amount.

[0012] The seismic sensor of the third invention is the seismic sensor of the first or second invention, wherein after a predetermined period of time has elapsed, the offset adjustment unit performs offset adjustment including origin correction of acceleration using an offset amount larger than the previous offset amount. As a result, if there is a large difference between the current offset amount and the previous offset amount within a specified period (e.g., 5 to 20 seconds) after the vibration has subsided, it is assumed that there is a high possibility that the seismic sensor remains tilted, and therefore an offset adjustment can be performed using a new offset amount. Therefore, if the seismic sensor remains tilted, an origin correction that takes the tilt into account can be performed, making it possible to perform appropriate corrections in the tilted state.

[0013] The seismic sensor of the fourth invention is the seismic sensor of the first or second invention, wherein the convergence determination unit determines whether or not the vibrations have converged after a predetermined time has elapsed following determination by the earthquake determination unit. This allows a determination to be made as to whether the detected vibrations are an earthquake, and after a predetermined time has elapsed, a determination to see whether the vibrations have subsided or not, making it easy to determine whether the vibrations have only caused the seismic sensor to tilt temporarily, or whether it remains tilted.

[0014] The seismic sensor of the fifth invention is the seismic sensor of the first or second invention, wherein when the origin correction necessity determination unit determines that origin correction is necessary, the offset adjustment unit performs origin correction of the acceleration in the horizontal plane to correct the directional deviation of the gravitational acceleration. This allows the origin of the acceleration in the horizontal plane, which has shifted due to the inclination of the seismic sensor, to be corrected, thereby taking into account the inclination of the seismic sensor and maintaining the accuracy of the determination.

[0015] The seismic sensor of the sixth invention is the seismic sensor of the first or second invention, wherein the offset adjustment unit adjusts the offset amount when the earthquake determination unit determines that the vibration is not an earthquake. This makes it possible to carry out appropriate offset adjustments depending on the magnitude of vibrations other than earthquakes.

[0016] The seismic sensor according to the seventh aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising a main body provided with an acceleration acquisition unit. The origin correction necessity determination unit determines whether or not the main body is tilted after the vibration has converged, depending on whether or not the offset amount is approximately the same as the previous offset amount. This makes it possible to easily determine whether the main body of the seismic sensor itself has tilted due to vibration by determining whether the newly calculated offset amount is approximately the same as the previous offset amount.

[0017] The seismic sensor of the eighth invention is a seismic sensor of the first or second invention, further comprising an acceleration waveform generating unit that generates an acceleration waveform showing the relationship between the acceleration acquired by the acceleration acquisition unit and elapsed time. This makes it possible to use the acceleration waveform generated from the acceleration of the detected vibration to perform earthquake determination, offset adjustment, determination of the need for origin correction, and the like.

[0018] 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, further comprising a frequency detection section that detects the frequency of the acceleration waveform generated in the acceleration waveform generation section. This makes it possible to use the frequency detected from the acceleration waveform to perform earthquake determination, offset adjustment, determination of the need for origin correction, and the like.

[0019] The seismic sensor according to a tenth aspect of the present invention is the seismic sensor according to the ninth aspect of the present invention, wherein the earthquake determination section determines whether or not the vibration is an earthquake based on the frequency detected by the frequency detection section. 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.

[0020] The seismic sensor of the 11th invention is the seismic sensor of the first or second invention, and further includes an earthquake magnitude calculation unit that, when the earthquake judgment unit judges that there is an earthquake, determines whether the earthquake is of a predetermined seismic intensity or greater. As a result, for example, if the earthquake scale is judged to be an upper 5 on the seismic intensity scale or higher, there is a risk of fire, gas leaks, etc., so a shutoff signal can be output to stop the supply of energy such as electricity or gas, thereby improving the safety of users.

[0021] The seismic sensor according to a twelfth aspect of the present invention is the seismic sensor according to the first aspect of the present invention, further comprising an output section that outputs a predetermined signal when the earthquake determination section determines that an earthquake has occurred. As a result, for example, when an earthquake occurs, a cutoff signal to stop the supply of energy such as electricity or gas, or a warning signal to notify of danger can be output from the output unit.

[0022] The seismic sensor of the 13th invention is the seismic sensor of the 11th invention, further comprising an output unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred, and further comprising an output control unit that controls the output of a signal from the output unit depending on whether the magnitude of the earthquake calculated in the earthquake magnitude calculation unit is equivalent to or greater than a predetermined seismic intensity. As a result, when the earthquake magnitude calculation unit calculates that the magnitude of the earthquake is, for example, a seismic intensity of 5+ (a specified seismic intensity) or greater, the output unit can output, for example, a cutoff signal to stop the supply of energy such as electricity or gas, or a warning signal to warn the user.

[0023] The seismic sensor according to a fourteenth aspect of the present invention is the seismic sensor according to the twelfth aspect of the present invention, wherein the predetermined signal is a shutoff signal that stops the supply of energy. This makes it possible, for example, to stop the supply of energy such as electricity and gas when an earthquake of a predetermined seismic intensity or greater is detected.

[0024] A seismic sensor according to a fifteenth aspect of the present invention is the seismic sensor according to the twelfth aspect of the present invention, wherein the predetermined signal is a warning signal that issues a warning to a user. This makes it possible, for example, to notify the user of danger by issuing a warning signal when an earthquake of a predetermined seismic intensity or greater is detected.

[0025] The seismic sensor according to a sixteenth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising a memory unit for storing the offset amount. This makes it possible to retrieve the previous offset amount from a memory unit installed within the seismic sensor and compare it with the newly calculated offset amount to determine whether or not origin correction is required.

[0026] The earthquake detection method according to the seventeenth aspect of the present invention includes an acceleration acquisition step, an earthquake determination step, an offset adjustment step, a convergence determination step, and an origin correction necessity determination step. In the acceleration acquisition step, vibration is detected and the acceleration of the vibration is acquired. In the earthquake determination step, it is determined whether the vibration is an earthquake or not based on the acceleration of the vibration acquired in the acceleration acquisition step. In the offset adjustment step, after detecting noise contained in the vibration detected in the earthquake determination step, an offset amount is adjusted according to the magnitude of the vibration. In the convergence determination step, it is determined whether the vibration has converged. In the origin correction necessity determination step, it is determined whether to perform origin correction of the acceleration depending on whether the offset amount calculated according to the magnitude of the vibration after the noise is detected is approximately the same as the previous offset amount when a predetermined period has elapsed since the time when it was determined that the vibration had converged in the convergence determination step.

[0027] Here, in an earthquake detection method that determines whether or not a vibration is an earthquake based on the acceleration of the detected vibration, and adjusts the offset amount to eliminate the effects of noise depending on the magnitude of the vibration after the noise is detected, the presence or absence of tilt of the seismic sensor is detected and a determination is made as to whether or not to perform an origin correction depending on whether the offset amount calculated after a predetermined period of time has elapsed (e.g., 5 to 20 seconds has elapsed) from the time when it is determined that the vibration has converged is approximately the same as the previous offset amount.

[0028] Here, the previous offset amount to be compared with the newly calculated offset amount based on the magnitude of vibration after noise is detected is the offset amount calculated the previous time vibration was detected, and means, for example, the offset amount stored in the seismic sensor. In addition, examples of vibrations that cause the seismic sensor to return to its original tilt after a predetermined period of time include low-frequency vibrations.

[0029] As a result, if it is determined that the current offset amount is approximately the same as the previous offset amount after a specified period of time has passed after the vibrations have subsided, it is presumed that the seismic sensor is almost not tilted, whereas if there is a large difference compared to the previous offset amount, it is presumed that there is a high possibility that the seismic sensor remains tilted. Therefore, after the vibration has subsided, if it continues for a predetermined time or more, the offset amount including origin correction is adjusted in that tilted state, and if the tilt does not continue for the predetermined time, the offset adjustment can be performed using a new offset amount with the tilt returned to its original state. As a result, the influence of a temporary tilt that occurs immediately after the occurrence of vibration is eliminated, and vibration can be determined with high accuracy.

[0030] An earthquake detection program according to an eighteenth aspect of the present invention causes a computer to execute an earthquake detection program including an acceleration acquisition step, an earthquake determination step, an offset adjustment step, a convergence determination step, and an origin correction necessity determination step. In the acceleration acquisition step, vibration is detected and the acceleration of the vibration is acquired. In the earthquake determination step, it is determined whether the vibration is an earthquake or not based on the acceleration of the vibration acquired in the acceleration acquisition step. In the offset adjustment step, after detecting noise contained in the vibration detected in the earthquake determination step, an offset amount is adjusted according to the magnitude of the vibration. In the convergence determination step, it is determined whether the vibration has converged. In the origin correction necessity determination step, it is determined whether to perform origin correction of the acceleration depending on whether the offset amount calculated according to the magnitude of the vibration after the noise is detected is approximately the same as the previous offset amount when a predetermined period of time has elapsed since the time when it was determined that the vibration had converged in the convergence determination step.

[0031] Here, in an earthquake detection program that determines whether or not a vibration is an earthquake based on the acceleration of the detected vibration, and adjusts the offset amount to eliminate the effects of noise depending on the magnitude of the vibration, the program detects whether or not the seismic sensor is tilted and determines whether or not to perform an origin correction depending on whether or not the offset amount calculated a predetermined period of time after it is determined that the vibration has converged (for example, 5 to 20 seconds) is approximately the same as the previous offset amount.

[0032] Here, the previous offset amount to be compared with the newly calculated offset amount based on the magnitude of vibration after noise is detected is the offset amount calculated the previous time vibration was detected, and means, for example, the offset amount stored in the seismic sensor. In addition, examples of vibrations that cause the seismic sensor to return to its original tilt after a predetermined period of time include low-frequency vibrations.

[0033] As a result, if it is determined that the current offset amount is approximately the same as the previous offset amount after a specified period of time has passed after the vibrations have subsided, it is presumed that the seismic sensor is almost not tilted, whereas if there is a large difference compared to the previous offset amount, it is presumed that there is a high possibility that the seismic sensor remains tilted. Therefore, after the vibration has subsided, if it continues for a predetermined time or more, the offset amount including origin correction is adjusted in that tilted state, and if the tilt does not continue for the predetermined time, the offset adjustment can be performed using a new offset amount with the tilt returned to its original state.

[0034] As a result, the influence of a temporary tilt that occurs immediately after the occurrence of vibration is eliminated, and vibration can be determined with high accuracy. Effect of the Invention

[0035] The seismic sensor according to the present invention can eliminate the influence of temporary tilt that occurs immediately after the occurrence of vibration, thereby making it possible to determine vibration with high accuracy. [Brief description of the drawings]

[0036] [Figure 1] FIG. 2 is a control block diagram showing the configuration of a seismic sensor according to one embodiment of the present invention. [Diagram 2] A functional block diagram generated within the seismic sensor of Figure 1. [Diagram 3] (a) is a graph showing an acceleration waveform when a predetermined period has passed since the detected vibration was determined not to be an earthquake and the offset amount remains larger than the previous offset amount. (b) is a graph showing an acceleration waveform when the offset amount, which was larger than the previous offset amount after the detected vibration was determined not to be an earthquake, approaches the previous offset amount after a predetermined period has passed. [Figure 4] (a) is a graph showing the state where the origin shift occurs in the horizontal plane (X-axis, Y-axis) due to the inclination of the seismic sensor. (b) is a graph showing the state where the acceleration on both the X-axis and Y-axis is offset by origin correction from the state of (a). [Diagram 5] 2 is a flowchart showing a main flow of processing of an earthquake detection method using the seismic sensor of FIG. 1. [Figure 6] 6 is a flowchart showing a detailed flow of the offset adjustment process in FIG. 5 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] A seismic sensor according to one embodiment of the present invention will be described below with reference to Figs. 1 to 6. In the present embodiment, more detailed explanations than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicate explanations of substantially the same configurations may be omitted. This is to avoid the following explanation from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description so that those skilled in the art can fully understand the present invention, and they are not intended to limit the subject matter described in the claims.

[0038] (1) Configuration of seismic sensor 10 As shown in FIG. 1, a seismic sensor 10 according to this embodiment includes an acceleration sensor 11, a controller 12, and a memory 13 in a main body 10a.

[0039] 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 scale of the earthquake.

[0040] Also, the controller 12 operates in different ways, either in an active mode or in a sleep mode, depending on the situation. The sleep mode is a mode in which the controller 12 operates with limited functions, such as halting execution of instructions while accepting interrupts, halting the supply of clocks, etc. In this sleep mode, it is possible to reduce power consumption more than in the active mode.

[0041] 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 scale of the earthquake is calculated. The function blocks (see FIG. 2) generated by the CPU in the seismic sensor 10 reading 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.

[0042] 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, for example, that 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 stop the supply of energy such as electricity or gas to an external device.

[0043] (2) Functional block of seismic sensor 10 As shown in FIG. 2, the seismic sensor 10 includes, within the main body 10a, an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a vibration intensity discrimination / activation determination unit 23, a frequency detection unit 24, an earthquake determination unit 25, a vibration stop period determination unit 26, an earthquake magnitude calculation unit 27, an output control unit 28, an offset adjustment unit 29, and a memory unit 30.

[0044] 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 usually acquires measurement data of acceleration repeatedly measured at a relatively low speed (i.e., at a relatively large measurement period). 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 in which it performs sampling at a low speed, so the controller 12 operates in a sleep mode with limited functionality to reduce power consumption.

[0045] Furthermore, when the acceleration acquisition unit 21 acquires a vibration 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 25 (described later) and the like execute processes, the controller 12 operates in an active mode (measurement mode). The transition from the power saving mode to the measurement mode is called the start-up of the seismic sensor 10.

[0046] 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 is switched from the sleep mode to the active mode, resulting in greater power consumption than in the power saving mode.

[0047] The acceleration waveform generating section 22 generates an acceleration waveform indicating the relationship between the acceleration measured by the acceleration acquiring section 21 and elapsed time. The vibration intensity discrimination / activation determination unit 23 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).

[0048] In addition, the vibration intensity discrimination / activation determination unit 23 is a function on the acceleration sensor 11 side, which calculates the vibration intensity from the results acquired by 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 a measurement mode which consumes more power than the power saving mode (activates the controller 12). Here, the vibration intensity discrimination process performed by the vibration intensity discrimination / activation determination unit 23 is implemented by performing a filtering process on the acceleration value acquired by the acceleration acquisition unit 21. At this time, the filtered acceleration is stored in the storage unit 30.

[0049] In the seismic sensor 10 of this embodiment, the vibration intensity discrimination / activation determination unit 23 that performs the filtering process functions as a so-called digital filter, and existing technology can be adopted for the filtering process. The vibration intensity discrimination / activation determination unit 23 functions as a low-pass filter, for example, by calculating a moving average of the absolute value of the acceleration. The frequency detection section 24 detects the frequency of the acceleration waveform generated by the acceleration waveform generation section 22 .

[0050] Based on the frequency detected by frequency detection unit 24, earthquake determination unit 25 discriminates whether the acceleration waveform from which the frequency is detected is subject to earthquake determination, and determines whether the vibration of the acceleration waveform is an earthquake or not. Specifically, if the acceleration waveform decays to a vibration equivalent to or less than a predetermined seismic intensity within a predetermined time (for example, maximum value-minimum value of vibration acceleration<100 gal), the earthquake judgment unit 25 excludes the acceleration waveform from being subject to earthquake judgment.

[0051] Furthermore, when the frequency of the detected acceleration waveform is equal to or greater than a predetermined value and the fluctuation in the period (frequency) is equal to or less than a predetermined value, the earthquake determination unit 25 excludes the acceleration waveform from the targets for earthquake determination. Furthermore, for example, when the amplitude of the acceleration waveform detected by the peak method is equal to or greater than a predetermined value and the frequency is equal to or greater than a predetermined value, the earthquake determination unit 25 excludes the acceleration waveform from the targets for earthquake determination.

[0052] In this embodiment, after an acceleration exceeding the activation threshold is detected, the earthquake determination unit 25 defines one or more determination periods and performs processing for each determination period. The vibration stop period determination unit 26 determines whether or not there is a period during which vibration has stopped in the acceleration waveform after the earthquake determination unit 25 has determined that an earthquake has occurred. The determination of whether or not there is a period in which vibration has stopped in the acceleration waveform may be made, for example, based on whether or not there is a period in which the acceleration has become zero, or based on whether or not the acceleration has fallen within a predetermined threshold range.

[0053] When the earthquake determination unit 25 determines that an earthquake has occurred, the earthquake scale calculation unit 27 determines whether the earthquake is equivalent to or exceeds a predetermined seismic intensity. In addition, 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 regarded as an impact is detected, the earthquake magnitude calculation unit 27 excludes the acceleration waveform and calculates the magnitude of the earthquake.

[0054] At this time, the frequency detection unit 24 detects a frequency used to determine whether or not the detected acceleration waveform can be regarded as an impact, for example, 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.

[0055] Here, the specified signal output from the output unit 14 includes, for example, a shutoff signal transmitted 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 section 25 determines that the vibration detected by acceleration acquisition section 21 is noise, offset adjustment section 29 adjusts the offset amount of the acceleration waveform each time noise is detected. Also, when earthquake determination section 25 determines that the vibration acquired by acceleration acquisition section 21 is not an earthquake, offset adjustment section 29 detects noise, calculates the offset amount according to the magnitude of the vibration, and performs offset adjustment of the acceleration waveform.

[0056] The offset adjustment performed by the offset adjustment unit 29 detects, as offset components, noise components contained in the measured acceleration, such as the amount of change in the measurement value that occurs with time-dependent changes 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 attitude of the installed seismic sensor 10 is tilted for some reason and the direction of gravitational acceleration relative to the seismic sensor 10 changes. Specifically, the offset adjustment unit 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.

[0057] In addition, offset adjustment is performed by calculating an offset amount according to the magnitude of vibration after noise is detected, and using the calculated offset amount the next time the seismic sensor 10 is started to eliminate the effects of noise. The calculated offset components are stored in the memory unit 30 and used for the start-up determination performed by the vibration intensity discrimination / start-up determination unit 23 and the earthquake determination performed by the earthquake determination unit 25. The offset amount adjusted by the offset adjustment unit 29 is feedback-controlled every time vibration is detected and an acceleration waveform is generated, and is updated and stored so that it becomes an appropriate value according to the amount of noise.

[0058] As a result, the offset amount is always set within an appropriate range, so that when detecting the frequency of the acceleration waveform, the frequency can be detected with high accuracy. As shown in FIG. 2, the offset adjustment unit 29 includes a convergence determination unit 29a and an origin correction necessity determination unit 29b. The convergence determination unit 29a determines whether the detected vibration has converged within a predetermined period (e.g., 1 second). Specifically, the convergence determination unit 29a determines whether the vibration has converged depending on whether all peak-to-peak values ​​(pp values) of the acceleration waveform are less than a predetermined threshold value (e.g., less than 100 gal) within the predetermined period.

[0059] Furthermore, the convergence determination unit 29a determines whether or not the vibration has converged after a predetermined time has elapsed following the determination in the earthquake determination unit 25. The origin correction necessity determination unit 29b determines whether or not to perform origin correction of the acceleration waveform (acceleration) depending on whether or not the offset amount calculated according to the magnitude of the vibration after noise is detected is approximately the same as the previous offset amount when a predetermined period of time (e.g., 5 to 20 seconds) has elapsed since the convergence determination unit 29a determined that the vibration has converged.

[0060] Then, the origin correction necessity determination unit 29b determines whether or not the seismic sensor 10 (main body 10a) is tilted after the vibration has converged, depending on whether or not the offset amount is approximately the same as the previous offset amount. In other words, the origin correction necessity determination unit 29b compares the offset amount calculated after the vibration has converged with the previous offset amount, and if it is determined that the offset amount is greater than the previous offset amount, it presumes that the tilt of the main body of the seismic sensor 10 has been maintained as it is, whereas if it is determined that the offset amount is equivalent to the previous offset amount, it presumes that the tilt of the main body of the seismic sensor 10 has almost disappeared.

[0061] Then, when the origin correction necessity determining section 29b determines that the offset amount is approximately the same as the previous offset amount, the offset adjusting section 29 performs offset adjustment using the new offset amount. Furthermore, when origin correction necessity determination unit 29b determines that the offset amount calculated at a point in time when a predetermined period of time has elapsed since the convergence of vibration (for example, when 5 to 20 seconds have elapsed) is greater than the previous offset amount, offset adjustment unit 29 performs offset adjustment including origin correction of the acceleration waveform using the calculated offset amount.

[0062] Here, when origin correction necessity determining unit 29b determines that origin correction is necessary, offset adjusting unit 29 performs origin correction of acceleration in a horizontal plane to correct a deviation in the direction of gravitational acceleration. That is, for example, when the vertical direction is the Z axis, offset adjusting unit 29 performs origin correction of acceleration in the X-axis and Y-axis directions (horizontal directions). More specifically, for example, as shown in FIG. 3(a), if the earthquake determination unit 25 determines that the vibration detected by the acceleration acquisition unit 21 is not an earthquake, and the calculated offset amount remains larger than the previous offset amount for 5 to 20 seconds, the offset adjustment unit 29 performs offset adjustment.

[0063] FIG. 3(a) shows an acceleration waveform obtained when the seismic sensor 10 is kept in an inclined position after vibration is detected and until a predetermined period of time has elapsed (e.g., 5 to 20 seconds) after the vibration has converged. In this case, the seismic sensor 10 is activated immediately after detecting the vibration, the earthquake determination unit 25 determines that it is a vibration and not an earthquake, and within a predetermined period of time (e.g., within 5 to 20 seconds) after the convergence determination unit 29a determines that the vibration has converged, the origin correction necessity determination unit 29b calculates an offset amount according to the magnitude of the vibration after noise contained in the acceleration waveform is detected, and determines whether origin correction is necessary.

[0064] In addition, when the origin correction necessity determining unit 29b determines that origin correction is necessary, this means that, for example, as shown in FIG. 4(a), in the horizontal plane (the X-Y axis plane when the vertical direction is the Z axis), the X-axis acceleration component and the Y-axis acceleration component caused by the tilt of the seismic sensor 10 need to be offset adjusted to bring them into the state shown in FIG. 4(b). At this time, the origin correction necessity determining unit 29b compares the calculated offset amount with the previous offset amount stored in the storage unit 30 to determine whether or not they are approximately the same magnitude.

[0065] 3(a), the offset amount calculated 5 to 20 seconds after the vibration convergence is greater than the previous offset amount stored in the memory unit 30, so it is presumed that the tilt of the seismic sensor 10 is being maintained, and so the origin correction necessity determining unit 29b determines that origin correction is necessary. Therefore, in this case, the offset adjusting unit 29 performs offset adjustment including origin correction using the offset amount calculated 5 to 20 seconds after the vibration convergence.

[0066] As a result, even if the seismic sensor 10 is caused to maintain an inclined position due to vibration, the inclination of the seismic sensor 10 can be taken into consideration to perform highly accurate vibration detection. Figure 3(b) shows an acceleration waveform when vibration, such as low-frequency vibration, is detected and the seismic sensor 10 is tilted by the vibration, and then returns to approximately its original position after the vibration converges.

[0067] In this case, the seismic sensor 10 is started immediately after detecting the vibration, the earthquake determination unit 25 determines that it is a vibration and not an earthquake, and the convergence determination unit 29a performs a convergence determination as to whether the vibration has converged or not. At the same time, the origin correction necessity determination unit 29b calculates an offset amount according to the magnitude of the vibration after detecting the noise included in the acceleration waveform, and performs the determination of whether origin correction is necessary. 3(b), the origin correction necessity determination unit 29b estimates that the tilt of the seismic sensor 10 was temporary, since the offset amount calculated after the vibration convergence has decreased to approximately the same as the previous offset amount stored in the memory unit 30. Therefore, in this case, the offset adjustment unit 29 performs offset adjustment using the newly calculated offset amount.

[0068] As a result, if the seismic sensor 10 is temporarily tilted due to vibration but returns to its original position after a specified period of time has elapsed, a new offset amount is used to perform offset adjustment, enabling highly accurate vibration detection. In the graph shown in FIG. 3(b), since the vibration is detected again after it has converged once, the offset adjustment is not performed until the vibration converges again, but is performed after the vibration has converged. The memory unit 30 stores, for example, acceleration data acquired by the acceleration acquisition unit 21, or acceleration data after filtering processing, the judgment result in the earthquake judgment unit 25, data of offset components (offset amount) used in the offset adjustment unit 29, etc.

[0069] <Earthquake detection method> The earthquake detection method using the seismic sensor 10 of this embodiment will be described below with reference to the flow charts of FIGS.

[0070] FIG. 5 is a process flow diagram showing an example of earthquake detection processing by the seismic sensor 10 of this embodiment. In the seismic sensor 10 of this embodiment, when acceleration equal to or greater than a predetermined value is detected, the sensor transitions from a standby state (power saving mode) to a measurement mode and performs earthquake determination processing. If it is determined that an earthquake has occurred, the sensor transitions to earthquake processing, and if the magnitude of the earthquake is equal to or greater than a certain level, a process of outputting a shutoff signal to related equipment is performed.

[0071] The process shown in FIG. In the seismic sensor 10, first, in step S11, various data such as various thresholds and offset amounts used in earthquake detection processing, which are stored in the memory 13 or storage unit 30 within the seismic sensor 10, are initially set. Next, in step S12, the standby state of the seismic sensor 10 is maintained. More specifically, the acceleration acquisition unit 21 of the seismic sensor 10 acquires the acceleration measured by the acceleration sensor 11 in the power saving mode (acceleration acquisition step). Note that, in the standby state, the acceleration acquisition unit 21 performs low-speed sampling.

[0072] Next, in step S13, the vibration intensity discrimination / activation determination unit 23 of the seismic sensor 10 determines whether or not to activate the seismic sensor 10 (that is, whether or not to transition from the power saving mode to the measurement mode). In this step, if the acceleration measured in the standby state is equal to or less than a predetermined activation threshold (a relative value based on the offset) (S13: NO), the process returns to step S12 and the standby state (power saving mode) continues. Here, the activation threshold is a value representing an acceleration such as 50 gal, which is initially set in step S11 and stored in the storage unit 30.

[0073] On the other hand, if the acceleration measured in the standby state is greater than the activation threshold (S13: YES), the acceleration acquiring unit 21 proceeds to earthquake determination processing (measurement mode) in step S 14. Note that the acceleration acquiring unit 21 performs high-speed sampling in the earthquake determination processing (measurement mode). Next, in step S14, the acceleration acquisition unit 21 measures the acceleration at high speed sampling in the earthquake determination process (measurement mode), performs filtering on the measured acceleration, and stores the resultant value in the storage unit 30 (earthquake determination process). Note that filtering may be performed by the controller 12 switching to the active mode, or may be performed by the acceleration sensor 11 while the controller 12 remains in the sleep mode. Also, filtering is not essential in the earthquake determination process.

[0074] Next, in step S15, it is determined whether the detected vibration is an earthquake (earthquake determination process). More specifically, earthquake determination unit 25 determines whether the detected vibration is an earthquake depending on whether the acceleration value measured in the earthquake determination process in step S14 satisfies a predetermined condition. The earthquake determination unit 25 determines that an earthquake has occurred, for example, when the difference between the maximum and minimum (peak-to-peak) values ​​of acceleration measured in a determination period is equal to or greater than a predetermined threshold value (for example, 100 gal).

[0075] Therefore, if it is determined in step S15 that an earthquake has occurred (S15: YES), the process proceeds to earthquake processing in step S17. Next, in the offset adjustment process of step S16, since the detected vibration is determined not to be an earthquake in the earthquake determination process of step S15, the offset adjustment unit 29 detects noise contained in the acceleration waveform indicating vibration, and then calculates an offset amount according to the magnitude of the vibration to perform offset adjustment.

[0076] In this step, as the offset adjustment process, for example, the offset amount is adjusted by obtaining the average value of acceleration from the acceleration waveform. Then, when the offset adjustment process in step S16 ends, the process returns to the standby state in step S12. The offset adjustment process in step S16 will be described in detail later with reference to the flow shown in FIG.

[0077] Next, in step S17, since the detected vibration is determined to be an earthquake in the earthquake determination process in step S15, the earthquake scale calculation unit 27 of the seismic sensor 10 calculates an evaluation index (for example, an SI value) indicating the scale of the earthquake. When calculating the evaluation index, the controller 12 operates in the active mode. If the calculated evaluation index is greater than a predetermined threshold value, it is determined that an earthquake of a predetermined intensity or greater has occurred, and an evaluation index (SI value) is output to an external device (not shown) equipped with the seismic sensor 10. Then, a cutoff signal for cutting off the supply of energy such as gas or electricity is output from the external device, and the gas or electricity is cut off.

[0078] Next, in step S18, it is determined whether or not the earthquake processing period has ended. This earthquake processing period is a period that is initially set in advance in step S11, and may be, for example, a period of 120 seconds. If it is determined in step S18 that the earthquake processing period has not yet ended, the process returns to step S17 and earthquake processing continues. On the other hand, if it is determined in step S18 that the earthquake processing period has ended, the process proceeds to step S19.

[0079] Next, in step S19, the earthquake processing is ended, the calculation of the SI value is also ended, and the SI value is reset. When the processing of step S19 is ended, the processing of this routine is temporarily ended. The seismic sensor 10 of this embodiment executes the offset adjustment process of step S16 included in the earthquake detection method shown in FIG. 5, according to the flowchart shown in FIG. The flowchart in FIG. 6 shows the flow of the offset adjustment process in the case where the detected vibration is not an earthquake, that is, it is determined to be vibration in step S15 of FIG. 5, and the process proceeds to step S16.

[0080] That is, in step S20, the acceleration information acquisition unit 21 acquires data on the acceleration of vibration, and the offset adjustment unit 29 calculates the amount of offset. Next, in step S21, if the detected vibration is not an earthquake, the offset adjustment unit 29 determines whether a predetermined time (e.g., 40 seconds) has elapsed since the activation of the seismic sensor 10. If the predetermined time has not elapsed, the process proceeds to step S22, and if the predetermined time has elapsed, the process transitions to a standby state.

[0081] Next, in step S22, since it is determined in step S21 that the predetermined time (e.g., 40 seconds) has not elapsed, in order to check the convergence state of the vibration, the convergence determination unit 29a determines whether the pp (peak-to-peak) values ​​of all accelerations in the predetermined period (e.g., 1 second) are less than a predetermined threshold value (e.g., 70 to 100 gal) (convergence determination step). Here, if the pp values ​​of all accelerations are less than the threshold value, the process proceeds to step S23, and if they are equal to or greater than the threshold value, the process returns to step S21.

[0082] Next, in step S23, since it was determined in step S22 that all the p-p values ​​of the accelerations are less than the threshold value, the origin correction necessity determination unit 29b determines whether or not a predetermined period (for example, 5 to 20 seconds) has passed since the vibration converged once (origin correction necessity determination step). Here, if the predetermined period has passed since the convergence, the process proceeds to step S24, and if the predetermined period has not passed, the process proceeds to step S25.

[0083] Next, in step S24, since it was determined in step S23 that a predetermined period (e.g., 5 to 20 seconds) has passed since the vibration converged once, origin correction necessity determination unit 29b determines whether or not it is a predetermined time (e.g., 5 to 20 seconds) since the convergence (origin correction necessity determination step). If it is a predetermined time (e.g., 5 to 20 seconds) since the vibration converged, the process proceeds to step S26, and if the predetermined period has passed, it is determined that vibration has been detected again during the determination and offset adjustment is impossible, and the process transitions to a standby state.

[0084] Next, in step S25, since it is determined in step S23 that a predetermined period has not elapsed since the vibration was once converged, the origin correction necessity determination unit 29b determines whether or not the difference between the offset amount calculated in step S20 and the previous offset amount is less than a predetermined threshold value (for example, 10 to 30 gal) (origin correction necessity determination step). If the difference is less than the threshold value, the process proceeds to step S26. On the other hand, if the difference is equal to or greater than the threshold value, it is determined that the current offset amount deviates from the previous offset amount, and the process returns to step S21 without performing offset adjustment, and the process from step S21 onwards is performed again.

[0085] As a result, until a predetermined period of time has elapsed since the vibration convergence, the process proceeds to step S25, where the current offset amount is compared with the previous offset amount to determine whether the difference is less than a threshold value (10 to 30 gal).If the difference is equal to or greater than the threshold value, the process of determining whether or not origin correction is necessary is repeated until the difference becomes less than the threshold value. Next, in step S26, since it has been determined in step S24 that a predetermined time has elapsed (for example, 5 to 20 seconds have elapsed) since the vibration has converged once, or since it has been determined in step S25 that the difference between the current offset amount and the previous offset amount is less than the threshold value, offset adjustment unit 29 performs offset adjustment using the offset amount calculated at the predetermined time, or performs offset adjustment using a new offset amount (calculated in step S20) whose difference from the previous offset amount is less than the threshold value (offset adjustment step). As a result, the judgment processes of steps S21 to S23 and S25 are repeated until a predetermined time has elapsed after the vibration has converged, and if the difference from the previous offset amount does not become less than the threshold value by the predetermined time after the vibration has converged, offset adjustment can be performed using the offset amount calculated when the predetermined period has elapsed.

[0086] <Main features> The seismic sensor 10 of this embodiment includes an acceleration acquisition unit 21, an earthquake determination unit 25, an offset adjustment unit 29, a convergence determination unit 29a, and an origin correction necessity determination unit 29b. The acceleration acquisition unit 21 detects vibration and acquires the acceleration of the vibration. The earthquake determination unit 25 determines whether the vibration is an earthquake or not based on the acceleration acquired by the acceleration acquisition unit 21. The offset adjustment unit 29 adjusts the offset amount according to the magnitude of the vibration after detecting noise contained in the vibration detected by the earthquake determination unit 25. The convergence determination unit 29a determines whether the vibration has converged. The origin correction necessity determination unit 29b determines whether to perform origin correction of the acceleration depending on whether the offset amount calculated according to the magnitude of the vibration after detecting noise is approximately the same as the previous offset amount when a predetermined period has elapsed since the convergence determination unit 29a determined that the vibration has converged.

[0087] As a result, if it is determined that the current offset amount is approximately the same as the previous offset amount after a predetermined period of time has passed after the vibrations have subsided (for example, after 5 to 20 seconds have passed), it is presumed that the seismic sensor is almost not tilted, but if the difference compared to the previous offset amount is large, it is presumed that there is a high possibility that the seismic sensor remains tilted. Therefore, after the vibration has subsided, if it continues for a predetermined time or more, the offset amount including origin correction is adjusted in that tilted state, and if the tilt does not continue for the predetermined time, the offset adjustment can be performed using a new offset amount with the tilt returned to its original state. As a result, the influence of a temporary tilt that occurs immediately after the occurrence of vibration is eliminated, and vibration can be determined with high accuracy.

[0088] [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.

[0089] (A) In the above embodiment, the present invention has been described as an example of a seismic sensor and an earthquake detection method, but the present invention is not limited to this. For example, the present invention may be realized as an earthquake detection program that causes a computer to execute the above-described earthquake detection method using a seismic sensor.

[0090] This earthquake detection program is stored in a memory (storage unit) mounted on 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, earthquake determination step, offset adjustment step, convergence determination step, and origin correction necessity determination step, thereby achieving the same effects as those described above. Furthermore, the present invention may be realized as a recording medium storing an earthquake detection program for a seismic sensor.

[0091] (B) In the above embodiment, an example was described in which the offset adjustment unit 29 calculates the offset amount according to the magnitude of the vibration after detecting noise contained in the vibration waveform when a predetermined period (for example, 5 to 20 seconds) has elapsed since it was determined that the detected vibration has converged, and the origin correction necessity determination unit 29b determines whether the offset amount is approximately the same as the previous offset amount. However, the present invention is not limited to this. For example, taking into account cases where the seismic sensor is tilted due to an external impact rather than a slow vibration waveform such as a low-frequency vibration, the offset amount may be calculated when a longer or shorter time has passed since the vibration converges, and compared with the previous offset amount.

[0092] (C) In the above embodiment, an example has been described in which the offset adjustment unit 29 adjusts the offset of the acceleration waveform when the earthquake determination unit 25 determines that the detected vibration is not an earthquake. However, the present invention is not limited to this. For example, even if the detected vibration is determined to be an earthquake, the offset adjustment may be performed as necessary.

[0093] (D) In the above embodiment, an example has been described in which the output control unit 28 controls the output unit 14 to output a cutoff signal to stop the supply of energy such as electricity and gas when the vibration detected as an earthquake is equivalent to or greater than a seismic intensity of 5+. However, the present invention is not limited to this. For example, the output control unit may be configured to control the output unit to output a warning signal to warn a user of the occurrence of an earthquake.

[0094] (E) In the above embodiment, an example was given in which the determination of whether or not to exclude the acceleration waveform generated by detecting the acceleration of vibration from the target of earthquake determination was performed depending on whether or not the frequency is 10 Hz or more. However, the present invention is not limited to this. For example, the predetermined value for determining whether or not to exclude an acceleration waveform from earthquake judgment is not limited to 10 Hz, but may be a value greater than 10 Hz or a value less than 10 Hz.

[0095] (F) In the above embodiment, an example was given in which the determination as to whether or not to exclude the acceleration waveform generated by detecting the acceleration of vibration from the target for earthquake determination was performed depending on whether or not the amplitude of the acceleration waveform was 700 gal or more. However, the present invention is not limited to this. For example, the judgment conditions regarding the amplitude of the acceleration waveform are not limited to the above numerical ranges, and may be other conditions.

[0096] (G) In the above embodiment, an example has been described in which whether or not an earthquake has occurred is determined based on the magnitude of the frequency of the acceleration waveform, as well as monotonic attenuation, periodic fluctuation, amplitude, the presence or absence of a vibration stop period, etc. However, the present invention is not limited to this. For example, as for the means for determining a factor other than the magnitude of the frequency of the acceleration waveform, at least one of the means described above, or a means other than the means described above, may be used.

[0097] (H) In the above embodiment, an example was described in which the present invention is applied to the seismic sensor 10 that performs earthquake determination, but the present invention is not limited to this.

[0098] For example, the present invention may be applied to various products in which an earthquake determination is not performed and the detection state of an acceleration sensor changes due to vibrations or the like. [Industrial Applicability]

[0099] The seismic sensor of the present invention has the effect of being able to eliminate the effects of temporary tilt that occurs immediately after vibration occurs and determine vibration with high accuracy, and therefore can be widely applied to various devices that detect the occurrence of earthquakes. [Explanation of symbols]

[0100] 10. Seismic Sensor 10a Main body 11 Acceleration Sensor 12 Controller 13. Memory 14 Output section 21 Acceleration acquisition section 22 Acceleration waveform generator 23 Vibration intensity classification / startup determination section 24 Frequency detection section 25 Earthquake Determination Department 26 Vibration stop period determination unit 27 Earthquake scale calculation department 28 Output control section 29 Offset adjustment section 29a Convergence judgment section 29b Origin correction necessity determination section 30 Storage section

Claims

1. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an earthquake determination unit that determines whether the vibration is an earthquake based on the acceleration acquired by the acceleration acquisition unit; an offset adjustment unit that detects noise contained in the vibration detected by the earthquake determination unit and then adjusts an offset amount according to the magnitude of the vibration; A convergence determination unit that determines whether the vibration has converged; an origin correction necessity determination unit that determines whether or not to perform origin correction of the acceleration depending on whether or not the offset amount calculated according to the magnitude of the vibration after the noise is detected is approximately the same as a previous offset amount, when a predetermined period of time has elapsed since the convergence determination unit determined that the vibration has converged; A seismic sensor having the following features.

2. When the offset amount is approximately the same as the previous offset amount, the offset adjustment unit performs offset adjustment using the new offset amount. The seismic sensor according to claim 1 .

3. the offset adjustment unit performs offset adjustment including origin correction of the acceleration by using the offset amount larger than a previous offset amount after the predetermined period has elapsed.

3. The seismic sensor according to claim 1 or 2.

4. The convergence determination unit determines whether or not the vibration has converged after a predetermined time has elapsed since the determination by the earthquake determination unit.

3. The seismic sensor according to claim 1 or 2.

5. When the origin correction necessity determining unit determines that origin correction is necessary, the offset adjusting unit performs origin correction of acceleration in a horizontal plane to correct a deviation in the direction of gravitational acceleration.

3. The seismic sensor according to claim 1 or 2.

6. The offset adjustment unit adjusts the offset amount when the earthquake determination unit determines that the vibration is not an earthquake.

3. The seismic sensor according to claim 1 or 2.

7. The acceleration acquisition unit may further include a main body portion provided with the acceleration acquisition unit, the origin correction necessity determination unit determines whether or not the main body is inclined after the vibration has converged, depending on whether or not the offset amount is approximately the same as a previous offset amount.

3. The seismic sensor according to claim 1 or 2.

8. The acceleration waveform generating unit generates an acceleration waveform indicating a relationship between the acceleration acquired by the acceleration acquiring unit and elapsed time.

3. The seismic sensor according to claim 1 or 2.

9. 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 8.

10. The earthquake determination unit determines whether or not the vibration is an earthquake based on the frequency detected by the frequency detection unit. The seismic sensor according to claim 9.

11. The apparatus further includes an earthquake scale calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake has an earthquake intensity of a predetermined level or more.

3. The seismic sensor according to claim 1 or 2.

12. The earthquake determination unit further includes an output unit that outputs a predetermined signal when it is determined that an earthquake has occurred. The seismic sensor according to claim 1 .

13. an output unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred; The apparatus further includes an output control unit that controls the output of the signal from the output unit depending on whether the magnitude of the earthquake calculated by the earthquake magnitude calculation unit is equal to or greater than a predetermined seismic intensity. The seismic sensor according to claim 11.

14. The predetermined signal is a shutoff signal that stops the supply of energy. The seismic sensor according to claim 12.

15. The predetermined signal is a warning signal that warns a user. The seismic sensor according to claim 12.

16. Further comprising a storage unit for storing the offset amount.

3. The seismic sensor according to claim 1 or 2.

17. an acceleration acquisition step of detecting vibration and acquiring an acceleration of the vibration; an earthquake determination step of determining whether or not the vibration is an earthquake based on the acceleration of the vibration acquired in the acceleration acquisition step; an offset adjustment step of adjusting an offset amount according to a magnitude of the vibration after detecting noise contained in the vibration detected in the earthquake determination step; a convergence determination step of determining whether or not the vibration has converged; an origin correction necessity determination step of determining whether or not to perform origin correction of the acceleration depending on whether or not the offset amount calculated according to the magnitude of the vibration after the noise is detected is approximately the same as a previous offset amount, when a predetermined period of time has elapsed since the time point at which it is determined in the convergence determination step that the vibration has converged; The earthquake detection method includes:

18. an acceleration acquisition step of detecting vibration and acquiring an acceleration of the vibration; an earthquake determination step of determining whether or not the vibration is an earthquake based on the acceleration of the vibration acquired in the acceleration acquisition step; an offset adjustment step of adjusting an offset amount according to a magnitude of the vibration after detecting noise contained in the vibration detected in the earthquake determination step; a convergence determination step of determining whether or not the vibration has converged; an origin correction necessity determination step of determining whether or not to perform origin correction of the acceleration depending on whether or not the offset amount calculated according to the magnitude of the vibration after the noise is detected is approximately the same as a previous offset amount, when a predetermined period of time has elapsed since the time point at which it is determined in the convergence determination step that the vibration has converged; An earthquake detection program that causes a computer to execute an earthquake detection method comprising the steps of:

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