Seismometer

Abstract

To provide a seismometer that can obtain a large output while reducing noise.SOLUTION: A sensor S1 and a sensor S2 are mounted so as to oppose each other across a base body 6. Therefore, the detection signal of the sensor S1 has the reverse phase (180-degree differential phase) of the detection signal of the sensor S2. Consequently, an approximate double-amplitude signal can be obtained by calculating a difference D12 between the reverse-phase signals. The same is true for a difference D34 between a sensor S3 and a sensor S4, or a difference D56 between a sensor S5 and a sensor S6. The difference D12 calculated above can be assigned as a vibration signal in the X-axis direction, the difference D34 as a vibration signal in the Y-axis direction, and the difference D56 as a vibration signal in the Z-axis direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seismometer, and more particularly to improving its accuracy. [Background technology]

[0002] Most seismometers are configured to observe earthquake motion in the east-west, north-south, and up-down directions by using three uniaxial sensors that are orthogonal to each other, or one integrated triaxial sensor. Because the accuracy of these sensors depends on the accuracy of each individual sensor, a sensor with extremely high accuracy was required.

[0003] In response to this, Patent Document 1 proposes an earthquake sensor in which sensors are arranged in an n x n array on a single substrate and their outputs are added together to obtain an output. Thermal noise contained in the simultaneous outputs of multiple sensors is uncorrelated and has a uniform noise density across all frequency ranges. Therefore, by electrically and directly adding the outputs of N sensors, the noise component decreases in proportion to the inverse of the square root of N, improving accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2009-31032 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while the above-described conventional technology can increase the detection output by addition and achieve uniform noise reduction across all frequency bands, it is not possible to reduce disturbance noise and the like that occurs at specific frequencies.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a seismometer that can solve the above problems and obtain a large output while reducing noise. [Means for solving the problem]

[0007] The following are some independent features of the present invention, which do not necessarily need to be combined but can be combined in any desired manner.

[0008] (1) A seismometer according to the present invention comprises first to sixth seismic measuring sensors having substantially the same characteristics; a base body configured as a rigid rectangular parallelepiped, in which the first seismic measuring sensor is attached to a first surface, the second seismic measuring sensor is attached to a second surface opposite the first surface, the third seismic measuring sensor is attached to a third surface, the fourth seismic measuring sensor is attached to a fourth surface opposite the third surface, the fifth seismic measuring sensor is attached to a fifth surface, and the sixth seismic measuring sensor is attached to a sixth surface opposite the fifth surface; and a processing circuit that obtains a seismic measurement output based on the 1-2 difference, the 3-4 difference, and the 4-5 difference.

[0009] Since the difference between the outputs of the seismic measurement sensors attached to the opposing surfaces is calculated, the detection output can be greatly reduced and noise can be reduced.

[0010] (2) The seismometer according to the present invention is characterized in that the first to sixth seismic measurement sensors are uniaxial seismic measurement sensors, and the processing circuit outputs the first-second difference, the third-fourth difference, and the fifth-sixth difference as three-axial components.

[0011] Therefore, each component of the three axes can be obtained.

[0012] (3) The seismometer according to the present invention is characterized in that the first to sixth seismic measurement sensors are triaxial seismic measurement sensors, and the first-second difference, the third-fourth difference, and the fifth-sixth difference are integrated to obtain a triaxial seismic measurement output.

[0013] Therefore, each component of the three axes can be obtained.

[0014] (4) A seismometer according to the present invention comprises first to fourth seismic measuring sensors having substantially the same characteristics; a base body on which the first seismic measuring sensor is attached to a first surface, the second seismic measuring sensor is attached to a second surface opposite the first surface, the third seismic measuring sensor is attached to a third surface perpendicular to the first surface, and the fourth seismic measuring sensor is attached to a fourth surface opposite the third surface; and a processing circuit that calculates a 1-2 difference as the difference between a first measurement output of the first seismic measuring sensor and a second measurement output of the second seismic measuring sensor, calculates a 3-4 difference as the difference between a third measurement output of the third seismic measuring sensor and a fourth measurement output of the fourth seismic measuring sensor, and obtains a seismic measurement output based on the 1-2 difference and the 3-4 difference.

[0015] Since the difference between the outputs of the seismic measurement sensors attached to the opposing surfaces is calculated, the detection output can be greatly reduced and noise can be reduced.

[0016] (5) The seismometer according to the present invention is characterized in that the first to fourth seismic measurement sensors are uniaxial seismic measurement sensors, and the processing circuit outputs the first-second difference and the third-fourth difference as components of two axes.

[0017] Therefore, it is possible to obtain a two-axis seismometer, for example, a seismometer that measures long-period vibrations.

[0018] (6) The seismometer according to the present invention is characterized in that the first to fourth seismic measurement sensors are triaxial seismic measurement sensors, and the first-second difference and the third-fourth difference are integrated to obtain a triaxial seismic measurement output.

[0019] Therefore, each component of the three axes can be obtained.

[0020] (7) A seismometer according to the present invention comprises first to fourth seismic measuring sensors having substantially the same characteristics, a base body on which the first seismic measuring sensor is attached to a first surface, the second seismic measuring sensor is attached to a second surface opposite to the first surface, the third seismic measuring sensor is attached to the first surface in an inverted position relative to the first seismic measuring sensor, and the fourth seismic measuring sensor is attached to the second surface in an inverted position relative to the second seismic measuring sensor, and calculates a first-third difference as the difference between a first measurement output of the first seismic measuring sensor and a third measurement output of the third seismic measuring sensor, The apparatus is equipped with a processing circuit that calculates a 2-4 difference as the difference between the second measurement output of the second earthquake measurement sensor and the fourth measurement output of the fourth earthquake measurement sensor, and obtains an earthquake measurement output based on the difference between the 1-3 difference and the 2-4 difference.

[0021] Since the difference between the outputs of the seismic measurement sensors mounted in reverse is calculated, the detection output can be increased and noise can be reduced.

[0022] (8) A seismometer according to the present invention comprises first to fourth seismic measuring sensors having substantially the same characteristics, a base body having the first and third seismic measuring sensors attached to a first surface and the second and fourth seismic measuring sensors attached to a second surface opposite the first surface, and calculates a first-second difference as the difference between a first measurement output of the first seismic measuring sensor and a second measurement output of the second seismic measuring sensor, and calculates a third-fourth difference as the difference between a third measurement output of the third seismic measuring sensor and a fourth measurement output of the fourth seismic measuring sensor; The apparatus is provided with a processing circuit that obtains an earthquake measurement output based on the difference between the first-second difference and the third-fourth difference.

[0023] Since the difference between the outputs of the seismic measurement sensors attached to the opposing surfaces is calculated, the detection output can be greatly reduced and noise can be reduced.

[0024] (9) A seismometer according to the present invention comprises first to fourth seismic measuring sensors having substantially the same characteristics; a base body on which the first seismic measuring sensor is attached to a first surface, the second seismic measuring sensor is attached to a second surface opposite the first surface, the third seismic measuring sensor is attached to a third surface perpendicular to the first surface, and the fourth seismic measuring sensor is attached to a fourth surface opposite the third surface; and a processing circuit that calculates a 1-3 difference as the difference between a first measurement output of the first seismic measuring sensor and a third measurement output of the third seismic measuring sensor, calculates a 2-4 difference as the difference between a second measurement output of the second seismic measuring sensor and a fourth measurement output of the fourth seismic measuring sensor, and obtains a seismic measurement output based on the 1-3 difference and the 2-4 difference.

[0025] Since the difference between the outputs of the seismic measurement sensors attached to the opposing surfaces is calculated, the detection output can be greatly reduced and noise can be reduced.

[0026] (10) The seismometer according to the present invention is characterized in that the first to fourth seismic measurement sensors are uniaxial seismic measurement sensors or triaxial seismic measurement sensors.

[0027] Thus, a seismometer with biaxial detection or a seismometer with triaxial detection can be obtained.

[0028] (11) A seismometer according to the present invention comprises a first seismic measuring sensor, a second seismic measuring sensor having substantially the same characteristics as the first seismic measuring sensor, a base body having the first seismic measuring sensor attached to a first surface and the second seismic measuring sensor attached to a second surface facing the first surface and located at a distance such that vibrations caused by the vibration measuring mechanism of the first seismic measuring sensor on the first surface do not affect detection, and a processing circuit that calculates the difference between the first measurement output of the first seismic measuring sensor and the second measurement output of the second seismic measuring sensor and obtains the seismic measurement output based on the difference.

[0029] Since the difference between the outputs of the seismic measurement sensors attached to the opposing surfaces is calculated, the detection output can be greatly reduced and noise can be reduced.

[0030] (12) The seismometer according to the present invention is characterized in that the first and second seismic measurement sensors are uniaxial seismic measurement sensors or triaxial seismic measurement sensors.

[0031] Thus, a seismometer for detecting one axis or a seismometer for detecting three axes can be obtained.

[0032] The concept of "device" includes not only what is constituted by one computer, but also what is constituted by multiple computers connected via a network, etc. Therefore, when the means of the present invention (or even a part of the means) is distributed among multiple computers, these multiple computers correspond to the device.

[0033] The term "program" is a concept that includes not only programs that can be executed directly by a CPU, but also programs in source format, compressed programs, encrypted programs, and programs that work in conjunction with an operating system to perform their functions. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 illustrates the structure of a seismometer according to an embodiment. [Figure 2] 1 is a diagram showing sensors S1, S3, and S5 attached to a base body 6. FIG. [Figure 3] FIG. 2 is a diagram showing the hardware configuration of a processing circuit 10. [Figure 4] 10 is a flowchart of a control program 36. [Figure 5] FIG. 10 is a diagram showing a hardware configuration of a processing circuit 10 according to another example. [Figure 6] FIG. 10 is a diagram showing the hardware configuration of the processing circuit 10 when a three-axis sensor is used as each sensor. [Figure 7]FIG. 10 is a diagram showing how a three-axis sensor is attached to a base body 6. [Figure 8] FIG. 10 is a diagram showing the configuration of a seismometer according to another example. [Figure 9] FIG. 10 is a diagram showing the configuration of a seismometer according to a second embodiment. [Figure 10] 10 is a flowchart of a control program 36. [Figure 11] FIG. 10 is a diagram showing the process of calculations until a detection output is obtained. DETAILED DESCRIPTION OF THE INVENTION

[0035] 1. First embodiment 1.1 Configuration and operation Figure 1 shows the structure of a seismometer 2 according to one embodiment of the present invention. A cubic base body 6 is provided within a housing 4 and is held by a support structure 8. The support structure 8 has, for example, four pillars for supporting each face of the base body 6, and these pillars are fixed to the outer frame of the support structure 8. Therefore, the base body 6 can be firmly fixed.

[0036] Single-axis sensors S1 to S6 are attached to six surfaces of the base body 6. In this embodiment, the single-axis sensors S1 to S6 have substantially the same functions. For example, sensors of the same model from the same manufacturer are used.

[0037] Although the uniaxial sensors S3 and S4 are attached in a direction perpendicular to the paper surface, they are not shown in the figure. Furthermore, it is preferable that the base body 6 has sufficient rigidity relative to the uniaxial sensors S1 to S6 so as to prevent unnecessary vibrations. Therefore, in this embodiment, the base body 6 is made of a metal material and is a solid cube.

[0038] The uniaxial sensors S1, S2, S5, and S6 each detect vibrations in the directions indicated by the dashed lines. The uniaxial sensors S3 and S4 each detect vibrations in the direction perpendicular to the paper surface. In this embodiment, capacitance-type acceleration sensors are used as the uniaxial sensors S1 to S6.

[0039] 2 is a perspective view showing the uniaxial sensors S1 to S6 attached to the base body 6. The uniaxial sensors S1 to S6 are attached to the six surfaces of the base body 6, respectively.

[0040] 1, a processing circuit 10 for processing the outputs from the uniaxial sensors S1 to S6 to generate seismic measurement outputs is provided inside the housing 4. The seismic measurement outputs generated by the processing circuit 10 are output from a terminal 12.

[0041] The outputs of the uniaxial sensors S1 to S6 are led to a processing circuit 10 by signal lines, and the earthquake measurement output from the processing circuit 10 is led to a terminal 12 by a signal line, but these are omitted in the figure.

[0042] 3 shows the hardware configuration of the processing circuit 10. A CPU 30 is connected to a memory 32, an A / D converter 34, a non-volatile memory 36, and an I / O port 38.

[0043] The output signals of the sensors S1 to S6 are provided to the A / D converter 34. The A / D converter 34 takes in the outputs from these six sensors at the same timing and converts them into digital data.

[0044] An operating system 40 such as TRON and a control program 36 are recorded in the non-volatile memory 36. The control program 36 performs its functions in cooperation with the operating system 40. Note that the control program 36 may operate independently without using the operating system 40.

[0045] Terminal 12 is connected to I / O port 38. Terminal 12 is supplied with not only earthquake measurement output (acceleration data and velocity data) as digital data, but also earthquake measurement output (acceleration data and velocity data) as D / A converted analog data. Note that the D / A converter is omitted.

[0046] 4 shows a processing flowchart of the control program 42. The CPU 30 receives the detection signals of the sensors S1 to S6 as digital data from the A / D converter 34 (step ST1).

[0047] Next, CPU 30 calculates the difference D12 between the detection signals of sensors S1 and S2 (step ST2). As shown in FIG. 1, sensors S1 and S2 are attached so as to face each other across base body 6. Therefore, the detection signals of sensors S1 and S2 are in opposite phase (phases shifted by 180 degrees). In the processing of step ST2, the difference between the opposite phase signals is calculated, so a signal with approximately double the amplitude can be obtained.

[0048] Furthermore, in this embodiment, sensors S1 and S2 are arranged so that their signals are in opposite phase, which makes it possible to efficiently reduce noise. The reason for this is as follows: sensors S1 and S2 are mounted opposite each other, so their detection signals are in opposite phase, but noise occurs in the same phase. Therefore, by taking the difference as described above, the amplitude of the detection signal is doubled, making it possible to cancel out the noise.

[0049] Next, CPU 30 calculates the difference D34 between the detection signals of sensors S3 and S4 (step ST3). As described above, sensors S3 and S4 are mounted opposite each other, so by calculating the difference, the amplitude of the detection signal can be doubled and noise can be canceled out.

[0050] Furthermore, CPU 30 calculates the difference D56 between the detection signals of sensors S5 and S6 (step ST4). As described above, sensors S5 and S6 are mounted opposite each other, so by calculating the difference, the amplitude of the detection signal can be doubled and noise can be canceled out.

[0051] The CPU 30 outputs the difference D12 calculated as above as a vibration signal in the X-axis direction, the difference D34 as a vibration signal in the Y-axis direction, and the difference D56 as a vibration signal in the Z-axis direction to the terminal 12 via the I / O port 38. The X-axis, Y-axis, and Z-axis are orthogonal to one another.

[0052] In addition, in this embodiment, the sensors are attached to the six faces of the cube, so that the six sensors can be attached in pairs facing each other in a compact manner.

[0053] 1.2 Other (1) In the above embodiment, a cube is used as the base body, but any shape having six mutually perpendicular faces, such as a rectangular parallelepiped, can be used.

[0054] (2) In the above embodiment, an acceleration signal (data) is output as the earthquake measurement output, but an RMS value of acceleration, a velocity signal (data), or the like may also be output.

[0055] (3) In the above embodiment, a capacitance type acceleration sensor is used as the seismic measurement sensor, but other acceleration sensors such as a piezoelectric acceleration sensor may also be used. Also, a sensor that detects vibrations other than an acceleration sensor may also be used.

[0056] (4) In the above embodiment, the outputs of the sensors S1 to S6 are provided to the A / D converter 34 of the processing circuit 10.

[0057] However, as shown in FIG. 5, a difference calculation circuit (such as a differential amplifier) ​​F12 may be provided to calculate the difference between the detection signals of a pair of sensors S1 and S2 as an analog signal. The output of the difference D12 by the difference calculation circuit F12 is provided to an A / D converter 34 and converted into digital data, and the difference D12 is converted into digital data. The same applies to the detection signals of sensors S3 and S4 and the detection signals of sensors S5 and S6. Therefore, according to this modification, the processing of steps ST2 to ST4 is unnecessary. Note that when configured as shown in FIG. 5, the difference calculation circuits F12, F34, and F56 may be provided on the base body 6. This is because providing them in positions close to the sensors S1 to S6 reduces the influence of noise.

[0058] (5) In the above embodiment, filtering to remove high-frequency noise is not performed. However, filtering to remove high frequencies unnecessary for earthquake measurement may be performed. For filtering, a hardware filter circuit may be used, or filtering may be performed by program processing by the CPU 30.

[0059] (6) In the above embodiment, three sensor pairs, consisting of sensors S1 to S6, are used. However, if detection is to be performed in only one axis or only two axes, only one sensor pair (sensors S1 and S2, or sensors S3 and S4, or sensors S5 and S6) or two sensor pairs may be used. For example, to detect long-period seismic motion, vertical detection may not be necessary, so only two sensor pairs, consisting of sensors S1 to S4, may be used.

[0060] (7) In the above embodiment, uniaxial sensors are used as the sensors S1 to S6, but biaxial or triaxial sensors may also be used.

[0061] Figure 6 shows the circuit configuration when using three-axis sensors S1 to S6. Each sensor outputs three detection signals, one for the X, Y, and Z directions. As shown in Figure 7, sensors S1 and S2 attached to base body 6 have opposite detection directions. That is, they are arranged so that the phases of the detection signals are opposite for the X, Y, and Z axes. Therefore, by detecting the differences between the X-axis detection signal, the Y-axis detection signal, and the Z-axis detection signal, it is possible to obtain X-axis, Y-axis, and Z-axis detection signals with doubled amplitude and reduced noise.

[0062] Similarly, detection signals for the X-axis, Y-axis, and Z-axis can be obtained from the difference between triaxial sensors S3 and S4, and detection signals for the X-axis, Y-axis, and Z-axis can be obtained from the difference between triaxial sensors S5 and S6. By adding up these three sets of detection signals for the X-axis, Y-axis, and Z-axis, one set of detection signals for the X-axis, Y-axis, and Z-axis can be obtained.

[0063] It is also possible to use only two or one sensor set instead of three. When only one or two sensor sets are provided, the base body 6 can be fixed directly to the housing 4 as shown in Fig. 8, thereby increasing rigidity.

[0064] (8) The above-described modifications can be implemented in combination with each other, and can be implemented in combination with other embodiments and their modifications.

[0065] 2. Second embodiment 2.1 Configuration and operation Figure 9A shows the structure of a seismometer according to the second embodiment. Figure 9B is a view from the top of the base body 6. As shown in the figure, uniaxial sensors S1 and S2 are provided on a first surface of the base body 6. Uniaxial sensors S3 and S4 are provided on a second surface.

[0066] The sensor S1 (sensor S3) is a uniaxial sensor similar to that of the first embodiment. The sensor S2 (sensor S4) has a sensor module housed therein that is housed in the opposite direction with respect to the detection direction. Therefore, although the sensors S1 and S2 (sensors S3 and S4) are attached to the same first surface (second surface), the phases of their detection signals are opposite.

[0067] The hardware configuration of the processing circuit 10 is the same as that of the first embodiment shown in Fig. 5. However, this embodiment differs in that sensors S1 to S4 are used.

[0068] 10 is a processing flowchart of the control program 42. The CPU 30 receives the detection signals of the sensors S1 to S4 as digital data from the A / D converter 34 (step ST11).

[0069] Next, CPU 30 calculates the difference D12 between the detection signals of sensors S1 and S2 (step ST12). As described above, the detection signals of sensors S1 and S2 are in opposite phase (180 degrees out of phase). In the process of step ST12, the difference between the opposite phase signals is calculated, so that a signal with approximately double the amplitude can be obtained, enabling efficient noise reduction.

[0070] Next, CPU 30 calculates a difference D34 between the detection signals of sensors S3 and S4 (step ST3). In this embodiment, difference D34 is calculated so that it has an opposite phase to difference D12. For example, if difference D12 is calculated using the positive direction of sensor S1 as the positive direction, difference D34 is calculated using the positive direction of sensor S4 (positioned inverted from sensor S1) as the positive direction.

[0071] The CPU 30 calculates the difference between the difference D12 and the difference D34 calculated as described above, and outputs the result as a detection signal, thereby further increasing the amplitude of the detection signal and reducing noise.

[0072] 1.2 Other (1) In the above embodiment, two sensors are provided on one surface of the base body 6. However, three or more sensors (for example, multiple pairs of sensors) may be provided on one surface.

[0073] For example, if sensors S1, S2, S3, and S4 are provided on one surface and sensors S5, S6, S7, and S8 are provided on the opposing surface, the final detection signal can be calculated as shown in Fig. 11. Note that sensors S1, S3, S5, and S7 are the same sensor, and sensors S2, S4, S6, and S8 are the same sensor except that their internal modules are provided facing in opposite directions.

[0074] The difference D12 (D56) and the difference D34 (D78) may be added together as being in phase. The same applies to D1234 and D5678.

[0075] Furthermore, in the above description, four sensors are provided on one surface and four sensors are provided on the opposing surface, but a pair of sensors may be provided on each of the six surfaces of the base body 6.

[0076] (2) In the above embodiment, the sensor S2 (S4) has an internal module facing in the opposite direction to the sensor S1 (S3). However, the sensor S2 (S4) may have an internal module facing in the same direction as the sensor S1 (S3). In this case, the sensors S1 and S3 are paired, and the sensors S2 and S4 are paired to calculate the difference.

[0077] (3) In the above embodiment, uniaxial sensors are used as the sensors S1 to S4, but biaxial or triaxial sensors may also be used.

[0078] (4) The above-described modifications can be implemented in combination with each other, and can be implemented in combination with other embodiments and their modifications.

Claims

1. First to sixth seismic measurement sensors having substantially the same characteristics; a base body configured as a rigid rectangular parallelepiped, the first seismic measurement sensor being attached to a first surface, the second seismic measurement sensor being attached to a second surface opposite to the first surface, the third seismic measurement sensor being attached to a third surface, the fourth seismic measurement sensor being attached to a fourth surface opposite to the third surface, the fifth seismic measurement sensor being attached to a fifth surface, and the sixth seismic measurement sensor being attached to a sixth surface opposite to the fifth surface; a processing circuit for obtaining a seismic measurement output based on the first-second difference, the third-fourth difference, and the fourth-fifth difference; A seismometer equipped with a

2. 2. The seismometer of claim 1, the first to sixth seismic measurement sensors are uniaxial seismic measurement sensors, The processing circuit outputs the first-second difference, the third-fourth difference, and the fifth-sixth difference as seismic measurement outputs, each of which is a component of three axes.

3. 2. The seismometer of claim 1, the first to sixth seismic measurement sensors are triaxial seismic measurement sensors, A seismometer characterized in that the first-second difference, the third-fourth difference, and the fifth-sixth difference are integrated to obtain a triaxial earthquake measurement output.

4. first to fourth seismic measurement sensors having substantially the same characteristics; a base body on which the first seismic measurement sensor is attached to a first surface, the second seismic measurement sensor is attached to a second surface opposite to the first surface, the third seismic measurement sensor is attached to a third surface perpendicular to the first surface, and the fourth seismic measurement sensor is attached to a fourth surface opposite to the third surface; calculating a first-second difference as a difference between a first measurement output of the first seismic measurement sensor and a second measurement output of the second seismic measurement sensor; calculating a third-fourth difference as a difference between a third measurement output of the third seismic measurement sensor and a fourth measurement output of the fourth seismic measurement sensor; a processing circuit for obtaining a seismic measurement output based on the first-second difference and the third-fourth difference; A seismometer equipped with a

5. 5. The seismometer of claim 4, the first to fourth seismic measurement sensors are uniaxial seismic measurement sensors, The seismometer is characterized in that the processing circuit outputs the first-second difference and the third-fourth difference as earthquake measurement components of two axes.

6. 5. The seismometer of claim 4, the first to fourth seismic measurement sensors are triaxial seismic measurement sensors, A seismometer characterized in that the first-second difference and the third-fourth difference are integrated to obtain a triaxial earthquake measurement output.

7. first to fourth seismic measurement sensors having substantially the same characteristics; a base body on which the first seismic measuring sensor is attached to a first surface, the second seismic measuring sensor is attached to a second surface opposite to the first surface, the third seismic measuring sensor is attached to the first surface in a position opposite to the first seismic measuring sensor, and the fourth seismic measuring sensor is attached to the second surface in a position opposite to the second seismic measuring sensor; calculating a first-third difference as a difference between a first measurement output of the first seismic measurement sensor and a third measurement output of the third seismic measurement sensor; calculating a second-fourth difference as a difference between the second measurement output of the second seismic measurement sensor and the fourth measurement output of the fourth seismic measurement sensor; a processing circuit for obtaining an earthquake measurement output based on the difference between the first-third difference and the second-fourth difference; A seismometer equipped with a

8. first to fourth seismic measurement sensors having substantially the same characteristics; a base body having the first seismic measurement sensor and the third seismic measurement sensor attached to a first surface and the second seismic measurement sensor and the fourth seismic measurement sensor attached to a second surface opposite to the first surface; calculating a first-second difference as a difference between a first measurement output of the first seismic measurement sensor and a second measurement output of the second seismic measurement sensor; calculating a third-fourth difference as a difference between a third measurement output of the third seismic measurement sensor and a fourth measurement output of the fourth seismic measurement sensor; a processing circuit for obtaining an earthquake measurement output based on the difference between the first-second difference and the third-fourth difference; A seismometer equipped with a

9. first to fourth seismic measurement sensors having substantially the same characteristics; a base body on which the first seismic measurement sensor is attached to a first surface, the second seismic measurement sensor is attached to a second surface opposite to the first surface, the third seismic measurement sensor is attached to a third surface perpendicular to the first surface, and the fourth seismic measurement sensor is attached to a fourth surface opposite to the third surface; calculating a first-third difference as a difference between a first measurement output of the first seismic measurement sensor and a third measurement output of the third seismic measurement sensor; calculating a second-fourth difference as a difference between the second measurement output of the second seismic measurement sensor and the fourth measurement output of the fourth seismic measurement sensor; a processing circuit for obtaining an earthquake measurement output based on the first-third difference and the second-fourth difference; A seismometer equipped with a

10. The seismometer according to any one of claims 7 to 9, The seismometer is characterized in that the first to fourth seismic measurement sensors are uniaxial seismic measurement sensors or triaxial seismic measurement sensors.

11. a first seismic measurement sensor; a second seismic measurement sensor having substantially the same characteristics as the first seismic measurement sensor; a base body having the first seismic measurement sensor attached to a first surface and the second seismic measurement sensor attached to a second surface facing the first surface and spaced apart from the first surface by a distance such that vibrations caused by a vibration measurement mechanism of the first seismic measurement sensor on the first surface do not affect detection; a processing circuit that calculates a difference between a first measurement output of the first seismic measurement sensor and a second measurement output of the second seismic measurement sensor, and obtains a seismic measurement output based on the difference; A seismometer equipped with a

12. The seismometer of claim 11, The seismometer is characterized in that the first and second seismic measurement sensors are uniaxial seismic measurement sensors or triaxial seismic measurement sensors.

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