Earthquake survey method, underground monitoring method, earthquake survey system and seismic center device

Abstract

To provide a technology enabling more accurate underground monitoring.SOLUTION: An earthquake survey method includes a vibration generation step of allowing a seismic center device 10 arranged underground to generate vibration, and an acquisition step of allowing a signal acquisition device 20 to acquire a vibration signal based on vibration generated by the seismic center device 10. The seismic center device 10 includes eccentric rotors 170, 180 that rotate around a rotation shaft, and a drive unit 160 that rotates the rotors to generate vibration.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a seismic exploration method, an underground monitoring method, a seismic exploration system, and a seismic source device. [Background technology]

[0002] Conventionally, geological structures have been explored by observing the propagation of artificially generated seismic waves. For example, Patent Document 1 describes a rotary seismic source device that supports a pair of eccentric rotors with the same eccentricity in parallel with each other, and drives both eccentric rotors at the same rotation speed in opposite directions with the phases matched so that the eccentric parts of both eccentric rotors are symmetrical to each other, thereby continuously generating seismic waves that reciprocate in one axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-142344 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inventors of the present application have come to recognize the following problem. When a rotating seismic source device is installed on the ground, the seismic waves are affected by the aboveground environment, and the accuracy of exploration of the geological structure decreases. For this reason, the technology described in Patent Document 1, which uses a rotating seismic source device installed on the ground, is unable to monitor the underground with high accuracy.

[0005] The present invention has been made in view of the above circumstances, and one of the exemplary objectives of the present invention is to provide a technique that enables more accurate underground monitoring. [Means for solving the problem]

[0006] One aspect of the present invention is a seismic exploration method. The seismic exploration method includes a vibration generating step in which a seismic source device disposed underground generates vibrations, and an acquisition step in which a signal acquiring device acquires a vibration signal based on the vibrations generated by the seismic source device. The seismic source device includes an eccentric rotor that rotates about a rotation axis, and a drive unit that generates vibrations by rotating the rotor.

[0007] Another aspect of the present invention is a method for monitoring underground, comprising the seismic exploration method described above.

[0008] Another aspect of the present invention is a seismic exploration system. The seismic exploration system includes a seismic source device that generates vibrations and a signal acquisition device that acquires vibration signals based on the vibrations generated by the seismic source device, the seismic source device having an eccentric rotating body that rotates about a rotation axis, and a drive unit that generates vibrations by rotating the rotating body.

[0009] Another aspect of the present invention is a seismic source device. The seismic source device includes a seismic source unit having an eccentric rotating body that rotates about a rotation axis and a drive unit that generates vibrations by rotating the rotating body, and a storage unit that stores the seismic source unit in an internal space. The storage unit stores the seismic source unit so that the seismic source unit can be attached and detached through an opening of the internal space.

[0010] Any combination of the above components and any conversion of the present invention into a method, device, system, etc. are also valid aspects of the present invention. Effect of the Invention

[0011] According to the present invention, a technique can be provided that enables more accurate underground monitoring. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a seismic exploration system according to a first embodiment. [Diagram 2] FIG. 2 is a functional block diagram of a management device according to the embodiment. [Diagram 3] 2 is a diagram showing a schematic configuration of the seismic exploration system according to the embodiment and a cross section of an underground area. FIG. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of a seismic source unit according to the embodiment. [Diagram 5] FIG. 2 is a schematic cross-sectional view of the epicenter according to the embodiment. [Figure 6] 4 is a flowchart showing an example of the operation of the seismic exploration system according to the embodiment. [Figure 7] FIG. 11 is a diagram showing a schematic configuration of a seismic exploration system according to a second embodiment and a cross section of an underground area. [Figure 8] FIG. 11 is a diagram showing a schematic configuration of a seismic exploration system according to a third embodiment and a cross section of an underground area. [Figure 9] FIG. 13 is a diagram showing a schematic configuration of a seismic exploration system according to a fourth embodiment and a cross section of an underground area. [Figure 10] FIG. 2 is a functional block diagram of the laser device according to the embodiment. [Figure 11] FIG. 13 is a diagram showing a schematic configuration of a seismic source unit according to a fifth embodiment. [Figure 12] FIG. 13 is a cross-sectional view showing a schematic configuration of a seismic source part according to the sixth embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a schematic configuration of a seismic source part according to the seventh embodiment. [Figure 14] FIG. 23 is a diagram showing a schematic view of a seismic source according to the eighth embodiment. [Figure 15] FIG. 13 is a perspective view of the seismic source unit according to the ninth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (background) In recent years, carbon capture and storage (CCS), a technology for processing carbon dioxide, a greenhouse gas, underground, has been attracting attention as a practical means. In CCS, carbon dioxide is injected underground using wells (hereinafter referred to as "injection wells") to send carbon dioxide from above ground, and the carbon dioxide is stored underground.

[0014] The International Energy Agency (IEA) has proposed a 15% reduction in carbon dioxide emissions by 2020. However, this 15% reduction is an ambitious target, and to achieve it through CCS, several thousand sites for storing large-scale carbon dioxide (hereinafter referred to as "CO2 storage sites") will be required around the world, and it is thought that around 240 to 480 injection wells will be required in Japan.

[0015] To ensure safety, it is necessary to monitor CO2 storage sites, but a practical method for doing so has not been established. In view of this situation, the inventors of the present application have come up with a seismic exploration system that can continuously monitor CO2 storage sites, as described in the following embodiments.

[0016] (Embodiment) Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the configurations described below are examples, and do not limit the scope of the present invention in any way.

[0017] In addition, in this specification and drawings, multiple components having substantially the same functional configuration may be distinguished by adding different alphabets after the same reference numeral. However, when there is no need to particularly distinguish between multiple components having substantially the same functional configuration, only the same reference numeral is added to each of the multiple components. In addition, in the description of the drawings, the same reference numeral is added to the same elements, and duplicated descriptions are omitted as appropriate. For example, when there is no particular distinction between the coupling mechanism 140a and the coupling mechanism 140b, they are simply referred to as "coupling mechanism 140".

[0018] (First embodiment) FIG. 1 is a schematic diagram of an earthquake exploration system 1 according to a first embodiment. As shown in FIG. 1, the earthquake exploration system 1 according to this embodiment includes a seismic source device 10, a signal acquisition device 20, and a management device 30. The earthquake exploration system 1 according to this embodiment performs underground monitoring based on earthquake exploration. Specifically, the earthquake exploration system 1 performs surveys of the geological structure by earthquake exploration multiple times at regular intervals. If there is a change in the underground condition during the survey interval, the earthquake exploration system 1 can capture the change as a difference in the results of the seismic exploration.

[0019] The seismic source device 10 according to this embodiment is placed in a hole formed in the ground and generates vibrations inside the hole. The seismic source device 10 generates vibrations with a waveform (chirp) including a wide frequency range, and the management device 30 performs cross-coherence analysis on the oscillation waveform recorded by a first receiver 20a (described later) installed near the seismic source device 10 and the waveform recorded by a second receiver 20b (described later) installed at a position away from the seismic source device 10. This makes it possible to obtain results equivalent to those obtained when an impulse source is generated by the seismic source device 10 and recorded by the second receiver 20b. The seismic source device 10 according to this embodiment generates vibrations by rotating an eccentric rotor that rotates around a rotation axis. The seismic source device 10 may be configured to drive a piston into a hole formed in the ground and generate vibrations underground by the impact of the piston.

[0020] The signal acquisition device 20 acquires a vibration signal based on the vibration generated by the seismic source device 10 and transmits the vibration signal to the management device 30. The signal acquisition device 20 may have various known seismometers, specifically, may have a receiver. In this embodiment, the signal acquisition device 20 has a first receiver 20a installed near the seismic source device 10 and a second receiver 20b installed at a position farther away from the seismic source device 10 than the first receiver 20a. The first receiver 20a acquires a first vibration signal based on the vibration generated by the seismic source device 10 and transmits the first vibration signal to the management device 30. The second receiver 20b acquires a second vibration signal based on the vibration generated by the seismic source device 10 and transmits the second vibration signal to the management device 30.

[0021] The management device 30 manages the operation of the earthquake exploration system 1. Specifically, the management device 30 controls the operation of the seismic source device 10, instructs the signal acquisition device 20 to acquire a vibration signal, and performs various processes based on the detection result of the signal acquisition device 20. For example, the management device 30 can supply power to the seismic source device 10 and cause the seismic source device 10 to generate vibrations. In addition, the management device 30 can transmit a trigger signal to instruct the receiver to record a vibration signal, record the vibration signal together with time information, and analyze the geology using the vibration signal from the signal acquisition device 20. The management device 30 may include a CPU (Central Processing Unit), a RAM (Read Access Memory), a ROM (Read Only Memory), and the like. In addition, the management device 30 may include a GPS (Global Positioning System) for recording accurate time.

[0022] 2 is a functional block diagram of the management device 30 according to the first embodiment. As shown in FIG. 2, the management device 30 according to the present embodiment includes a processing unit 300, a storage unit 320, an output unit 340, a communication unit 360, and a power supply unit 380.

[0023] The processing unit 300 performs various processes, specifically, transmits a control signal to the seismic source device 10, receives a vibration signal from the signal acquiring device 20, and performs arithmetic processing using the vibration signal. The functions of the processing unit 300 are realized by the control unit 302, the receiving unit 304, and the arithmetic unit 306. The control unit 302, the receiving unit 304, and the arithmetic unit 306 may be prepared separately.

[0024] The control unit 302 transmits a control signal to the seismic source device 10 and controls the operation of the seismic source device 10. Specifically, the control unit 302 may control the operating conditions of the motor of the seismic source device 10 (for example, the rotation speed, etc.).

[0025] The receiving unit 304 receives the vibration signal from the signal acquiring device 20 and transmits the vibration signal to the calculation unit 306. The calculation unit 306 performs various calculation processes based on the vibration signal and transmits the results to the storage unit 320 and the output unit 340. For example, the calculation unit 306 may perform processing related to geological analysis based on the vibration signal.

[0026] The calculation unit 306 according to this embodiment analyzes the vibration signals (first and second vibration signals) acquired by the two geophones (the first and second geophones 20a and 20b). Specifically, the calculation unit 306 synchronizes the first and second vibration signals, and performs geological analysis using various known analysis techniques based on these synchronized vibration signals.

[0027] More specifically, the calculation unit 306 uses the first vibration signal as an original function and acquires an original signal for analyzing the geology based on the first vibration signal and the second vibration signal using a cross-coherence technique (see the following document). The calculation unit 306 can analyze the geology using this original signal.

[0028] Nakata, N., Snieder, R., Tsuji, T., Larner, K., Matsuoka, T. (2011). Shear wave imaging from traffic noise using seismic interferometry by cross-coherence. Geophysics, 76:SA97-SA106. https : / / doi.org / 10.1190 / geo2010-0188.1

[0029] The storage unit 320 stores various information. For example, the storage unit 320 may store a control program for the control unit 302 to control the seismic source device 10, a calculation program for the calculation unit 306 to perform various calculations, and the calculation results of the calculation unit 306.

[0030] The output unit 340 outputs various information. The output unit 340 may be configured with various known display devices or audio output devices. For example, the output unit 340 may display the calculation results of the calculation unit 306. Specifically, the output unit 340 may display an image for monitoring the CO2 storage site.

[0031] The communication unit 360 is a communication interface for transmitting and receiving various information to and from other devices. For example, the communication unit 360 may transmit the analysis results by the calculation unit 306 to other devices. The communication unit 360 may also be used to remotely control the device.

[0032] The power supply unit 380 supplies power to the seismic source device 10. The power supply unit 380 may convert power from a commercial power source (not shown) as necessary and supply the power to the seismic source device 10. The power supply unit 380 may also supply power to the management device 30. Furthermore, in the case of a small seismic source device, a 12V DC battery may be used. In that case, power may be supplied from a solar panel.

[0033] 3 is a diagram showing a schematic configuration of the earthquake exploration system 1 according to the first embodiment and a cross section of the underground. The earthquake exploration system 1 according to this embodiment includes a seismic source unit 12 disposed underground, a geophone 20b (second geophone) disposed on the ground 422, and a management device 30.

[0034] The seismic source unit 12 according to this embodiment includes a seismic source device 10 and a receiver 20a (first receiver). The seismic source device 10 of the seismic source unit 12 can generate vibrations in response to control by the management device 30. The receiver 20a acquires a first vibration signal based on the vibrations generated by the seismic source device 10, and transmits the acquired first vibration signal to the management device 30.

[0035] In this embodiment, a hole 42 (also called a "well") extending vertically is formed in the ground. The seismic source unit 12 according to this embodiment is disposed inside this hole 42, and the seismic source unit 12 can be taken out of or inserted into the hole 42 as necessary. The depth d at which the seismic source unit 12 is disposed in the hole 42 is not particularly limited, but may be, for example, about 100 m or 1000 m deep. Furthermore, the seismic source units may be installed at multiple points at different depths to perform oscillation operations. Furthermore, if the seismic source unit can be installed near the object to be monitored, more accurate data can be obtained.

[0036] In this embodiment, an aquifer 43, which is a stratum filled with groundwater, is formed underground. The hole 42 according to this embodiment is formed so as to penetrate this aquifer 43. Therefore, groundwater from the aquifer 43 is stored in the hole 42.

[0037] The seismic source unit 12 may be disposed at a position deeper than the aquifer 43. When the seismic source unit 12 is disposed at a position higher than the aquifer 43 and is normally disposed at a position higher than the water surface, the water level of the groundwater stored in the hole 42 may change due to rainfall or the like, and the operation of the seismic source unit 12 (for example, the vibration generated) may be affected by the change in the groundwater, resulting in a decrease in the accuracy of monitoring. On the other hand, by disposing the seismic source unit 12 at a position deeper than the groundwater surface (for example, the water surface 432 of the aquifer 43 shown in FIG. 3) as in this embodiment, the seismic source unit 12 is submerged in the groundwater regardless of the change in the groundwater level due to rainfall or the like, so that it is possible to suppress the effect of the change in the groundwater level on monitoring.

[0038] The receiver 20b acquires a second vibration signal based on the vibration generated by the seismic source unit 12, and transmits the acquired second vibration signal to the management device 30. The management device 30 according to this embodiment can analyze, for example, geology based on the vibration signal including the first vibration signal and the second vibration signal transmitted from the receiver 20a and the receiver 20b. In addition, it is possible to monitor changes occurring underground from the time change of the vibration signal. In this embodiment, the receiver 20b is one, but it is preferable to install multiple receivers (for example, 100). In particular, multiple receivers are required when performing reflection seismic exploration, refraction seismic exploration, or surface wave seismic exploration.

[0039] 3 shows an example in which the seismic exploration system 1 includes one seismic source unit 12 disposed in one hole 42. However, multiple holes may be formed, and in this case, the seismic exploration system 1 may include multiple seismic source units disposed in the multiple holes, respectively. This allows vibrations to be generated at more points, making it possible to analyze the geology of a wider area and monitor the underground.

[0040] 4 is a diagram showing a schematic configuration of the seismic source unit 12 according to the first embodiment. The Z axis indicates the vertical direction, and the X and Y axes indicate the horizontal directions. The X axis is a direction perpendicular to the Z axis, and the Y axis is a direction perpendicular to the Z and X axes.

[0041] The seismic source device 10 according to this embodiment mainly comprises a storage section 100, a support body 120, a seismic source section 130, and coupling mechanisms 140a and 140b.

[0042] The storage unit 100 stores the support 120, the seismic source unit 130, and the receiver 20b. The storage unit 100 has a cylindrical shape, and may be, for example, about 10 cm long and about 10 cm in diameter. The storage unit 100 includes a housing 102 and a lid 104, and an internal space 106 surrounded by the housing 102 and the lid 104 is formed inside the storage unit 100.

[0043] Housing 102 has a hollow cylindrical shape extending in the Z-axis direction, with one lower end closed by a bottom portion 103 that constitutes part of housing 102 and one upper end closed by a lid portion 104.

[0044] The lid 104 is fixed to the housing 102 so that the opening at the top of the housing 102 can be opened and closed. When the lid 104 is closed, the inside of the storage unit 100 is sealed, and groundwater accumulated in the hole 42 does not enter the internal space 106. When the lid 104 is opened, the support 120 can be removed from the housing 102.

[0045] Various sensors (not shown) may be arranged in the storage unit 100. For example, a temperature sensor, a water pressure sensor, and the like may be arranged. These sensors may be connected to the management device 30 and arranged so as to be able to transmit measurement results relating to temperature, water pressure, and the like to the management device 30.

[0046] The support 120 has a hollow cylindrical shape extending in the Z-axis direction, and supports the seismic source unit 130 and the receiver 20b therein. The support 120 is detachably fixed to the housing 102 of the storage unit 100. The support 120 may be fixed directly to the housing 102, or may be fixed to the housing 102 via a fixing device. Note that, although FIG. 4 shows a gap between the storage unit 100 and the support 120 in the internal space 106, there may be no gap between the storage unit 100 and the support 120. For example, the support 120 is preferably fixed in a state of intimate contact with the housing 102.

[0047] The epicenter unit 130 generates vibrations used in earthquake exploration. The epicenter unit 130 according to this embodiment includes a motor (drive unit) and an eccentric rotating body, and vibrations are generated by the motor rotating the rotating body. A cable 31 connected to the management device 30 is connected to the epicenter unit 130. Power is supplied to the motor of the epicenter unit 130 from the management device 30 through the cable 31, and a control signal is transmitted thereto. This enables the epicenter unit 130 to generate vibrations.

[0048] A first vibration signal based on the vibration generated by the epicenter 130 is acquired by a geophone 20a installed inside the housing 100. The vibration generated by the epicenter 130 is transmitted to the periphery of the hole 42 via the side of the housing 100 or the coupling mechanisms 140a and 140b. A second vibration signal based on this vibration is acquired by a geophone 20b installed on the ground, for example. The first vibration signal based on the vibration of the epicenter 130 may be recorded by a geophone installed inside the housing 100.

[0049] The conditions of the vibration generated by the seismic source unit 130 can be adjusted by replacing various parts of the seismic source unit 130. For example, the conditions of the vibration can be adjusted by changing the motor of the seismic source unit 130, the gear for transmitting the driving force of the motor to the rotor, and the weight of the weight described below for making the rotor eccentric.

[0050] When replacing parts of the seismic source section 130, first, the seismic source unit 12 is taken out from the hole 42 to the ground. Then, the cover 104 is opened, and for example, the fasteners that fix the support 120 to the housing 102 are released, and the support 120 is taken out from the housing 102. Then, by replacing each part of the seismic source section 130, the conditions of the vibration generated by the seismic source section 130 can be adjusted. By placing the seismic source unit 12 in the hole 42 again after replacing the parts, it becomes possible to cause the seismic source section 130 to generate vibrations under new conditions.

[0051] The coupling mechanisms 140a and 140b couple the housing 102 of the accommodation unit 100 to the inner circumferential surface 420 of the hole 42. The coupling mechanisms 140a and 140b have substantially the same configuration as each other.

[0052] The coupling mechanism 140 has a pressing part 142 and a coupling part 144. One end of the pressing part 142 is connected to the housing 102, extends in a direction away from the housing 102, and the other end is connected to the coupling part 144. The pressing part 142 is configured to be able to press the coupling part 144 against the inner circumferential surface 420 of the hole 42. Specifically, the pressing part 142 is configured to be able to expand and contract in the horizontal direction (for example, the Y-axis direction), and presses the coupling part 144 by extending in the direction indicated by the arrow in FIG. 4. The configuration for the pressing part 142 to press the coupling part 144 is not particularly limited, and may be, for example, a water pressure type or an electrically controlled type. When the pressing part 142 has an electrically controlled pressing mechanism, the strength of the force with which the pressing mechanism presses the coupling part 144 may be adjusted by the management device 30 controlling the pressing mechanism.

[0053] When the pressing parts 142a and 142b press the coupling parts 144a and 144b against the inner circumferential surface 420 of the hole 42, the storage part 100 is coupled to the inner circumferential surface 420 of the hole 42. This allows the vibration generated by the seismic source part 130 to be transmitted to the surroundings via the storage part 100, the coupling mechanism 140, and the inner circumferential surface 420 of the hole 42 more reliably.

[0054] Here, an example has been described in which two coupling mechanisms 140a, 140b are provided on the housing 102, but the number of coupling mechanisms may be one or three or more. Also, an example has been described in which the coupling mechanism couples the accommodating unit 100 to the inner circumferential surface 420 in one direction (Y-axis direction), but this is not limiting, and multiple coupling mechanisms may be provided so that the accommodating unit 100 is coupled to the inner circumferential surface 420 in multiple different directions. For example, multiple coupling mechanisms may be provided in a circumferential line on the outer circumferential surface of the housing 102 to couple the accommodating unit 100 in multiple directions.

[0055] 5 is a schematic cross-sectional view of the seismic source unit 130 according to the first embodiment. As shown in FIG. 5, the seismic source unit 130 according to this embodiment includes a motor 160 (drive unit), a first rotating body 170, and a second rotating body 180.

[0056] The motor 160 is driven according to the control of the management device 30, and transmits the driving force to the first rotating body 170. The motor 160 according to this embodiment has a main body 162, a rotating shaft 164, and a transmission unit 166. A part of the rotating shaft 164 is housed in the main body 162. The rotating shaft 164 extends in the X-axis direction, and is configured to be rotatable about its length. The transmission unit 166 has a cylindrical shape extending in the X-axis direction, is disposed so as to cover the rotating shaft 164, and is configured to be rotatable integrally with the rotating shaft 172.

[0057] The motor 160 may be provided with a speed sensor (not shown). The speed sensor may be connected to the management device 30 to measure the rotation speed of the rotating shaft 164 and transmit the measurement result to the management device 30.

[0058] The first rotating body 170 has a rotating shaft 172, a transmitted part 174, a weight support part 176, a gear 178, and a weight 179. The rotating shaft 172 extends in the X-axis direction, and is configured to be rotatable about its length. The transmitted part 174 has a cylindrical shape extending in the X-axis direction, is disposed so as to cover the rotating shaft 172, and is configured to be rotatable integrally with the rotating shaft 172. In addition, a belt 168 is provided around the transmitting part 166 and the transmitted part 174.

[0059] The disk-shaped weight support portion 176 is provided around the transmitted part 174 and is configured to be rotatable integrally with the transmitted part 174. The disk-shaped gear 178 is provided around the transmitted part 176 and is configured to be rotatable integrally with the transmitted part 174. A weight 179 is provided on a part of the circumference of the weight support portion 176. Due to this weight 179, the first rotating body 170 is eccentric from its center (the position of the rotation axis 172 on the YZ plane) to the center of the weight 179. In the state shown in FIG. 5, the first rotating body 170 is eccentric to a position r1 away from its center in the Y-axis direction.

[0060] The second rotating body 180 has a rotating shaft 182, a weight support portion 184, a gear 186, and a weight 188. The rotating shaft 182 extends in the X-axis direction, and is configured to be rotatable about its length. The disk-shaped weight support portion 184 is provided around the rotating shaft 182, and is configured to be rotatable integrally with the rotating shaft 182. The disk-shaped gear 186 is provided around the weight support portion 184, and is configured to be rotatable integrally with the weight support portion 184. The gear 186 is also arranged to fit with the gear 178.

[0061] A weight 188 is provided on a portion of the circumference of weight support portion 184. This weight 188 causes second rotating body 180 to be eccentric from its center (the position of rotation axis 182 on the YZ plane) to the center of weight 188. In the state shown in Fig. 5, second rotating body 180 is eccentric to a position r2 away from its center in the direction opposite to the Y axis.

[0062] In this embodiment, the mass of weight 179 and the mass of weight 188 are equal to each other at m1. Weight 179 and weight 188 are arranged on first rotating body 170 and second rotating body 180 so that the amount of eccentricity is equal to each other. That is, weight 179 and weight 188 are arranged so that m1×r1=m1×r2.

[0063] When the motor 160 is driven, the rotating shaft 164 rotates, and in response to this rotation, the transmitting unit 166 rotates together with the rotating shaft 164. At this time, the driving force is transmitted from the transmitting unit 166 to the transmitting unit 174 via the belt 168. As a result, the transmitting unit 174 rotates in the clockwise direction around the rotating shaft 172 together with the other members constituting the first rotating body 170. At this time, the gear 186 of the second rotating body 180 receives the driving force from the gear 178 of the first rotating body 170. As a result, the gear 186 rotates in the opposite direction (counterclockwise direction) to the first rotating body 170 together with the other members constituting the second rotating body 180 around the rotating shaft 182.

[0064] Focusing on the movements of weights 179 and 188 when first rotor 170 and second rotor 180 rotate, horizontal (e.g., Y-axis) components of the rotational speeds of weights 179, 188 cancel each other out, and vertical (Z-axis) components of the rotational speeds of weights 179, 188 reinforce each other. Therefore, seismic source unit 130 can generate vertical vibrations by rotating first rotor 170 and second rotor 180 by driving motor 160.

[0065] The epicenter 130 according to this embodiment generates the same vibrations continuously and superimposes the vibrations. This allows the vibrations to reach distant locations even if the energy of the generated vibrations is small. The epicenter 130 can transmit vibrations up to 1 km away even if the weight of the weight is about 10 g.

[0066] The rotation speed of the rotating shaft 164 is not particularly limited, but may be a speed at which vibrations of about 20 to 60 Hz are generated. In general, the higher the frequency of the vibration, the higher the resolution of the seismic exploration, and the lower the frequency of the vibration, the less the vibration is attenuated and the more distant the vibration can be transmitted. It is preferable that the vibration has a wide frequency range.

[0067] The various components of the seismic source unit 130 described above can be appropriately replaced in order to adjust the vibration conditions. For example, the weight of the weights 179, 188 may be changed to adjust the vibration conditions depending on the object of monitoring in the seismic exploration. For example, if the object of monitoring is a dam, the weight of the weights 179, 188 may be about 10 g. If the object of monitoring is a wide area or deep, the weight of the weights may be about 100 g.

[0068] 6 is a flowchart showing an example of the operation of the earthquake exploration system 1 according to the first embodiment. Hereinafter, the example of the operation of the earthquake exploration system 1 will be described with reference to the flowchart.

[0069] First, the management device 30 transmits a control signal to the seismic source device 10 (S101). Next, the seismic source device 10 generates vibrations based on the control signal transmitted in S101 (S103: vibration generation step). Next, the signal acquisition device 20 acquires a vibration signal based on the vibrations generated in S103 (S105: signal acquisition step). Next, the signal acquisition device 20 transmits the vibration signal acquired in S105 to the management device 30 (S107). Next, the management device 30 acquires the vibration signal (S109) and analyzes the vibration signal (S111).

[0070] The processing of each step shown in the flowchart of Fig. 6 does not necessarily have to be performed in the order shown in Fig. 6. The order of each step may be changed or multiple steps may be processed in parallel as long as there is no logical contradiction. In addition, by repeatedly and continuously performing the processing of S101 to S109, it is possible to increase the S / N ratio of the vibration signal.

[0071] (Effects of this embodiment) Previously, seismic devices installed on the ground have been developed. However, the effects of rainfall, snow, and other elements near the ground surface have a strong influence on the results of seismic survey monitoring. In particular, when repeatedly conducting seismic surveys of geological structures and monitoring minute changes, the effects of the ground environment arise. For this reason, seismic surveys using conventional seismic devices are easily affected by the ground surface, making it difficult to monitor geological changes.

[0072] According to the earthquake exploration system 1 of this embodiment, the management device 30 can perform earthquake exploration using vibration signals based on vibrations generated from the earthquake source device 10 installed underground. Therefore, according to the earthquake exploration system 1 of this embodiment, the influence of the aboveground environment can be suppressed compared to the case of monitoring using vibrations from a earthquake source device installed on the ground, and therefore more accurate monitoring is possible.

[0073] Furthermore, with the seismic exploration system 1 according to this embodiment, since the target to be monitored is located underground, vibrations can be generated at a position closer to the target. Therefore, with the seismic exploration system 1 according to this embodiment, it becomes possible to monitor the underground by seismic exploration with higher accuracy.

[0074] Furthermore, the seismic exploration system 1 according to the present embodiment enables environmentally friendly monitoring. Specifically, the seismic exploration system 1 according to the present embodiment generates vibrations underground, which makes it possible to reduce noise caused by vibrations compared to generating vibrations above ground. Therefore, the seismic exploration system 1 according to the present embodiment can be used in urban areas and at night.

[0075] Conventional seismic source devices (e.g., Vibroseis) used in seismic exploration are huge, making operation in places with poor access difficult and expensive. In contrast, the seismic exploration system 1 according to this embodiment uses a small seismic source unit 12 to generate vibrations even in limited places with poor access. Therefore, the seismic exploration system 1 according to this embodiment makes it possible to perform seismic exploration at low cost in a wider variety of locations. For example, by digging many holes, placing the seismic source unit 12 according to this embodiment in each hole, and analyzing the vibration signals based on the vibrations generated by the seismic source units 12, many CO2 storage sites can be monitored simultaneously.

[0076] In addition, conventional seismic source devices are not designed for constant installation and cannot be used for continuous underground monitoring. In seismic exploration using conventional seismic source devices, monitoring is generally performed, for example, once every few years. In contrast, according to the seismic exploration system 1 according to this embodiment, the seismic source unit 12 is small, so that it can be installed on a regular basis. In addition, since the seismic source unit 12 has a mechanism for continuously generating vibrations, regular and continuous underground monitoring is possible. For example, by constantly monitoring a CO2 storage site, it is possible to respond to sudden CO2 leaks, etc.

[0077] In addition, conventionally, attempts have been made to generate vibrations by placing a seismic source device using a piezoelectric element underground. However, when using a piezoelectric element, the vibration is weak, and it has not been possible to realize vibrations strong enough for seismic exploration. In contrast, according to the seismic exploration system 1 of this embodiment, by rotating an eccentric rotor and strengthening the coupling between the seismic source unit 12 and the inner surface 420 of the hole 42 by the coupling mechanism 140, it is possible to generate vibrations of sufficient strength to monitor the underground by seismic exploration.

[0078] When installing a seismic source device on the surface of the moon, the coupling between the seismic source device and the lunar surface is weaker than on Earth due to the low gravity environment. According to the seismic exploration system 1 of this embodiment, the seismic source unit 12 is coupled to a hole formed in the ground using a coupling mechanism, so that stable vibrations can be generated while achieving good coupling even in low gravity.

[0079] The seismic exploration system 1 according to this embodiment can also be used for monitoring reservoirs under the seabed. Since the surface of the seabed is soft, even if a seismic source device is placed on the surface to generate vibrations, the vibrations are greatly attenuated, making it difficult to perform good seismic exploration. In contrast, the bedrock deep on the seabed is harder than the surface. For this reason, according to the seismic exploration system 1 according to this embodiment, a hole is drilled in the seabed, a seismic source device is inserted into the ground, and the device is fixed to the hard bedrock, thereby suppressing vibration attenuation and enabling accurate underground monitoring even on the seabed.

[0080] The seismic exploration system 1 according to this embodiment can be used for various applications, including the above-mentioned examples. For example, the seismic exploration system 1 can be used in the resource energy and decarbonization fields, such as monitoring of stored CO2 distribution and induced earthquakes at a CO2 underground storage site, monitoring of reservoirs for carbon neutrality such as underground CO2 storage and underground hydrogen storage, monitoring of geothermal reservoirs, monitoring of groundwater, and monitoring of resource reservoirs in oil and gas development, in the civil engineering field, such as monitoring the soundness of civil engineering structures such as levees, tunnels, and dams, in outer space such as the surface of the moon and Mars, and imaging of the underground in difficult-to-access areas such as mountainous regions.

[0081] Second embodiment 7 is a diagram showing a schematic configuration and an underground cross section of the earthquake exploration system 2 according to the second embodiment. The earthquake exploration system 2 according to the second embodiment includes three seismic source units 14a to 14c, a geophone 22 (second geophone), and a management device 32. The geophone 22 and the management device 32 may have substantially the same configurations as the geophone 20b and the management device 30 described in the first embodiment, respectively.

[0082] Each of the seismic source units 14a to 14c may have substantially the same configuration as the seismic source unit 12 described in the first embodiment, and can generate vibrations. The seismic source units 14a to 14c according to the second embodiment are disposed in one hole 44, and more specifically, are arranged in the direction in which the hole 44 extends (i.e., the vertical direction). Although three seismic source units are shown in FIG. 7, two seismic source units may be arranged, or four or more seismic source units may be arranged.

[0083] The vibration signal based on the vibration generated by the seismic source unit 14 is acquired by the geophone (first geophone) and the geophone 22 included in the seismic source unit 14. The management device 32 can perform analysis using the vibration signal. Therefore, the management device 32 can analyze the geology using the vibration signal based on the vibration generated by each of the seismic source units 14a to 14c. In addition, by changing and characterizing the waveform of the vibration generated by each of the multiple seismic source units 14, it becomes possible to distinguish and analyze the vibration from each of the multiple seismic source units 14 even when the multiple seismic source units 14 oscillate simultaneously.

[0084] By using the multiple seismic source units 14a-14c in this way, it becomes possible to perform more detailed seismic exploration. In addition, by arranging the multiple seismic source units 14a-14c in the direction in which the hole 44 extends, it becomes possible to perform underground monitoring by seismic exploration with higher spatial resolution.

[0085] Third embodiment 8 is a diagram showing a schematic configuration and an underground cross section of the earthquake exploration system 3 according to the third embodiment. The earthquake exploration system 3 according to the third embodiment includes a seismic source unit 16, a receiver 24 (second receiver), and a management device 34. The seismic source unit 16, the receiver 24, and the management device 34 may have substantially the same configurations as the seismic source unit 12, the receiver 20b, and the management device 30 described in the first embodiment, respectively.

[0086] As shown in Fig. 8, in the third embodiment, two holes 46a and 46b extending in the vertical direction are formed in the ground. The seismic source unit 16 is disposed in one hole 46a, and the receiver 24 is disposed in the other hole 46b. Thus, in the third embodiment, the receiver 24 is disposed underground, unlike the above-mentioned embodiments.

[0087] The geophone (first geophone) provided in the seismic source unit 16 acquires a first vibration signal based on the vibration generated by the seismic source unit 16. The geophone 24 acquires a second vibration signal based on the vibration generated by the seismic source unit 16. The management device 34 receives the vibration signals (first vibration signal and second vibration signal) and performs analysis based on the vibration signals. At this time, since the geophone 24 is placed underground, the vibration signal acquired by the geophone 24 is less affected by the aboveground environment. Therefore, according to the seismic exploration system 3 of this embodiment, it is possible to monitor changes underground with greater accuracy.

[0088] 8, only the seismic source unit 16 is shown in the hole 46a, and only the receiver 24 is shown in the hole 46b. However, the present invention is not limited to this. In addition to the seismic source unit 16, a receiver and other seismic source units may be placed in the hole 46a, and in addition to the receiver 24, a seismic source unit and other receivers may be placed in the hole 46b. Furthermore, multiple seismic source units 16 may be installed in the hole 46a, and multiple receivers may be installed in the hole 46b.

[0089] (Fourth embodiment) 9 is a diagram showing a schematic configuration of the seismic exploration system 4 according to the fourth embodiment and a cross section of the underground. The seismic exploration system 4 according to the fourth embodiment includes a seismic source unit 18, a signal acquisition device 26, and a management device 36. The seismic source unit 18 may have substantially the same configuration as the seismic source unit 12 according to the first embodiment, but may not have the receiver 20a. The management device 36 may have substantially the same configuration as the management device 30 according to the first embodiment.

[0090] The signal acquisition device 26 according to the fourth embodiment includes a laser device 37 and an optical fiber 260. The laser device 37 emits a laser beam to the optical fiber 260, and acquires a vibration signal based on the vibration generated by the seismic source unit 18 based on the laser beam reflected by the optical fiber 260. The laser device 37 transmits the acquired vibration signal to the management device 36.

[0091] As shown in Fig. 9, in the fourth embodiment, two holes 48a, 48b extending vertically are formed in the ground. The seismic source unit 18 is disposed in one hole 48a, and the optical fiber 260 is disposed in the other hole 48b along the direction in which the hole 48b extends.

[0092] 10 is a functional block diagram of a laser device 37 according to the fourth embodiment. As shown in FIG.

[0093] The light source 370 emits a laser beam and may be, for example, any of various known laser beam source devices. In this embodiment, the light source 370 emits a laser beam to the optical fiber 260. As a result, the laser beam is propagated in the optical fiber 260, and at least a part of the laser beam is reflected and returned to the laser device 37.

[0094] The acquisition unit 372 acquires a vibration signal based on the laser light propagated in the optical fiber 260. Specifically, the acquisition unit 372 has a light receiving unit, and detects the laser light reflected in the optical fiber 260 and returning to the laser device 37 with the light receiving unit. At this time, if the seismic source unit 18 generates vibration, the optical fiber 260 expands and contracts in the length direction in response to the vibration. Since the state of the laser light returning to the laser device 37 changes due to the expansion and contraction of the optical fiber 260, the acquisition unit 372 can acquire a vibration signal based on the vibration generated by the seismic source unit 18 by detecting the optical laser of the optical fiber 260.

[0095] According to the seismic exploration system 4 of this embodiment, a vibration signal can be obtained using the optical fiber 260 arranged in the hole 48b. In this case, by using the optical fiber 260, it is possible to realize a function similar to that of a case where a plurality of seismometers are arranged at regular intervals in the hole 48b. For example, when the length of the optical fiber 260 arranged in the hole 48 is 1000 m, it is possible to obtain a vibration signal equivalent to that obtained when the seismometers are arranged every 10 m. Therefore, according to the seismic exploration system 4 of this embodiment, it is possible to perform detailed underground monitoring by seismic exploration at low cost without using a large number of seismometers. Furthermore, since the optical fiber 260 is arranged underground, it is possible to suppress the vibration signal from being affected by the ground surface.

[0096] 9 shows an example in which only the optical fiber 260 is arranged in the hole 48b, but a seismic source unit may be arranged in the hole 48b. In this case, it is also possible to use the optical fiber 260 to obtain a vibration signal based on the vibration generated by the seismic source unit arranged in the same hole 48b.

[0097] Fifth embodiment 11 is a diagram showing a schematic configuration of the seismic source unit 19 according to the fifth embodiment. The seismic source unit 19 according to the fifth embodiment differs from the seismic source unit 12 according to the first embodiment mainly in the configuration of the coupling mechanism.

[0098] The seismic source unit 19 according to the fifth embodiment includes a storage section 100, a support body 120, a seismic source section 130, a receiver 20a, and a coupling mechanism 62.

[0099] The coupling mechanism 62 according to the fifth embodiment has an arm structure and is connected to the storage unit 100. Specifically, the coupling mechanism 62 extends in a direction away from the storage unit 100, and one end of the coupling mechanism 62 is connected to the storage unit 100 via a joint unit (not shown) configured to be rotatable around an axis (e.g., the X-axis) parallel to a horizontal plane. Therefore, the coupling mechanism 62 is rotatable around the joint unit. The operation of the coupling mechanism 62 may be electrically controlled based on a control signal from a management device arranged on the ground, for example.

[0100] 11 so that the other end 622 approaches the inner circumferential surface 490 of the hole 49. When the other end 622 of the coupling mechanism 62 comes into contact with and presses the inner circumferential surface 490 of the hole 49, the seismic source unit 19 is coupled to the inner circumferential surface 490 of the hole 49. This allows the vibrations generated by the seismic source unit 19 to be transmitted to the periphery of the hole 49 via the side surface of the housing part 100 or the coupling mechanism 62 more reliably.

[0101] Sixth embodiment Fig. 12 is a cross-sectional view showing a schematic configuration of the seismic source unit 70 according to the sixth embodiment. Fig. 12 shows the seismic source unit 70 as viewed in the horizontal direction (the X-axis direction in Fig. 12). As shown in Fig. 12, the seismic source unit 70 according to the sixth embodiment includes a motor 700, a first rotating body 720, and a second rotating body 740.

[0102] Motor 700 has a main body 702, a rotating shaft 704, and a transmission unit 706. A portion of rotating shaft 704 is housed in main body 702. Rotating shaft 704 extends in the X-axis direction and is configured to be rotatable about its length. Transmission unit 706 has a cylindrical shape extending in the X-axis direction, is provided so as to cover rotating shaft 704, and is configured to be rotatable integrally with rotating shaft 704.

[0103] The first rotating body 720 has a rotating shaft 722, a transmitted part 724, a weight support part 726, a gear 728, and a weight 729. The rotating shaft 722 extends in the X-axis direction, and is configured to be rotatable about its length. The transmitted part 724 has a cylindrical shape extending in the X-axis direction, is disposed so as to cover the rotating shaft 722, and is configured to be rotatable integrally with the rotating shaft 722. In addition, a belt 708 is provided around the transmitting part 706 and the transmitted part 724 so that a driving force is transmitted from the transmitting part 706 to the transmitted part 724.

[0104] A disk-shaped weight support portion 726 is provided around the transmitted force receiving portion 724 and configured to be rotatable integrally with the transmitted force receiving portion 724. A disk-shaped gear 728 is provided around the transmitted force receiving portion 726 and configured to be rotatable integrally with the transmitted force receiving portion 724. A weight 729 is provided on a part of the circumference of the weight support portion 726. Due to this weight 729, the first rotating body 720 is eccentric from its center (the position of the rotation axis 722 on the YZ plane) to the center of the weight 729. In the state shown in FIG. 12, the first rotating body 720 is eccentric to a position r3 away from its center in the Y-axis direction.

[0105] The second rotating body 740 has a rotating shaft 742, a weight support portion 744, a gear 746, and a weight 748. The rotating shaft 742 extends in the X-axis direction, and is configured to be rotatable about its length. The disk-shaped weight support portion 744 is provided around the rotating shaft 742, and is configured to be rotatable integrally with the rotating shaft 742. The disk-shaped gear 746 is provided around the weight support portion 744, and is configured to be rotatable integrally with the weight support portion 744.

[0106] A weight 748 is provided on a portion of the circumference of weight support portion 744. This weight 748 causes second rotating body 740 to be eccentric to a position away from its center (the position of rotation axis 742 on the YZ plane). In the state shown in Fig. 12, second rotating body 740 is eccentric to a position r4 away from its center in the Y-axis direction.

[0107] In this embodiment, the mass of weight 729 and the mass of weight 748 are equal to each other at m2. Weight 729 and weight 748 are arranged on first rotating body 720 and second rotating body 740 so that the amount of eccentricity is equal to each other. Therefore, weight 729 and weight 748 are arranged so that m2×r3=m2×r4.

[0108] When the motor 700 is driven, the rotating shaft 704 rotates, and in response to this rotation, the transmitting unit 706 rotates together with the rotating shaft 704. At this time, the driving force is transmitted from the transmitting unit 706 to the transmitted unit 724 via the belt 708. As a result, the transmitted unit 724 rotates in the clockwise direction around the rotating shaft 722 together with the other members constituting the first rotating body 720. At this time, the gear 746 of the second rotating body 740 receives the driving force from the gear 728 of the first rotating body 720, and the gear 746 rotates in the opposite direction (counterclockwise direction) to the first rotating body 720 together with the other members constituting the second rotating body 740 around the rotating shaft 742.

[0109] Focusing on the movements of weights 729 and 748 when first rotor 720 and second rotor 740 rotate, the vertical (Z-axis) components of the rotational speeds of weights 729, 748 cancel each other out, and the horizontal (e.g., Y-axis) components of the rotational speeds of weights 729, 748 reinforce each other. As a result, seismic source 70 can generate horizontal vibrations by rotating first rotor 720 and second rotor 740 by driving motor 700.

[0110] In this manner, the seismic source section 70 according to this embodiment can generate vibrations having a component in one direction on a horizontal plane, and this vibration can be used for seismic exploration.

[0111] Seventh embodiment 13 is a cross-sectional view showing a schematic diagram of the seismic source unit 75 according to the seventh embodiment. The seismic source unit 75 according to the seventh embodiment mainly includes a motor 750, a first rotor 760, a second rotor 770, a third rotor 780, and a fourth rotor 790. The seismic source unit 75 according to the seventh embodiment differs from the seismic source unit 130 according to the first embodiment mainly in that the seismic source unit 75 according to the seventh embodiment includes the third rotor 780 and the fourth rotor 790.

[0112] The configurations of the motor 750, first rotating body 760 and second rotating body 770 in the seventh embodiment are substantially identical to those of the motor 160, first rotating body 170 and second rotating body 180 in the first embodiment, and therefore detailed description thereof will be omitted here.

[0113] The third rotating body 780 has a rotating shaft 782, a transmitted part 784, a weight support part 786, a gear 788, and a weight 789. The rotating shaft 782 extends in the X-axis direction, and is configured to be rotatable about its length. The transmitted part 784 has a cylindrical shape extending in the X-axis direction, is disposed so as to cover the rotating shaft 782, and is configured to be rotatable integrally with the rotating shaft 782. In this embodiment, the radius of the transmitted part 784 of the third rotating body 780 is smaller than the radius of the transmitted part 764 of the first rotating body 760.

[0114] In this embodiment, a belt 758 is provided so that a driving force is transmitted from a transmission unit 754 of the motor 750 to a transmitted part 784 and a transmitted part 764 of the first rotating body 760. Specifically, the belt 758 is provided around the transmitted part 784, the transmission unit 754, and the transmitted part 764.

[0115] A disk-shaped weight support portion 786 is provided around the transmitted part 784 and is configured to be rotatable integrally with the transmitted part 784. A disk-shaped gear 788 is provided around the transmitted part 786 and is configured to be rotatable integrally with the transmitted part 784. A weight 789 is provided on a part of the circumference of the weight support portion 786. Due to this weight 789, the third rotating body 780 is eccentric from its center (the position of the rotation axis 782 on the YZ plane) to the center of the weight 789. In the state shown in FIG. 13, the third rotating body 780 is eccentric to a position r5 away from its center in the opposite direction to the Y-axis direction.

[0116] The fourth rotating body 790 has a rotating shaft 792, a weight support portion 794, a gear 796, and a weight 798. The rotating shaft 792 extends in the X-axis direction, and is configured to be rotatable about its length. The disk-shaped weight support portion 794 is provided around the rotating shaft 792, and is configured to be rotatable integrally with the rotating shaft 792. The disk-shaped gear 796 is provided around the weight support portion 794, and is configured to be rotatable integrally with the weight support portion 794.

[0117] A weight 798 is provided on a portion of the circumference of weight support portion 794. This weight 798 causes fourth rotating body 790 to be eccentric to a position away from its center (the position of rotation axis 792 on the YZ plane). In the state shown in Fig. 13, fourth rotating body 790 is eccentric to a position r5 away from its center in the Y-axis direction.

[0118] In this embodiment, the mass of weight 789 and the mass of weight 798 are equal to each other and are m3. Note that m3 may be lighter than weight 769 of first rotating body 760 and weight 778 of second rotating body 770. Weights 789 and 798 are arranged in third rotating body 780 and fourth rotating body 790 so that the amount of eccentricity is equal to each other. Therefore, weights 789 and 798 are arranged so that m3×r5=m3×r5.

[0119] In this embodiment, when the motor 750 is driven, the transmission part 754 rotates, and the driving force is transmitted to the transmission part 764 of the first rotating body 760 and the transmission part 784 of the third rotating body 780. At this time, the first rotating body 760 and the second rotating body 770 generate vertical vibrations in the same manner as in the first embodiment.

[0120] The transmitted part 784 of the third rotating body 780 receives the driving force of the motor 750 and rotates in the clockwise direction around the rotation shaft 782 together with the other members constituting the third rotating body 780. At this time, the gear 796 of the fourth rotating body 790 receives the driving force from the gear 788 of the third rotating body 780, and the gear 796 rotates in the opposite direction (counterclockwise direction) to the third rotating body 780 around the rotation shaft 792 together with the other members constituting the fourth rotating body 790. At this time, the horizontal components of the rotational speeds of the weights 789 and 798 cancel each other out, so that the third rotating body 780 and the fourth rotating body 790 generate vertical vibrations.

[0121] The transmitted part 784 of the third rotating body 780 receives the driving force of the motor 750 and rotates about the rotation shaft 782. At this time, since the radius of the transmitted part 784 is smaller than the radius of the transmitted part 764, the transmitted part 784 rotates faster than the transmitted part 764. As a result, the pair of the third rotating body 780 and the fourth rotating body 790 (hereinafter also referred to as the "second pair") generates vibrations at a higher frequency than the pair of the first rotating body 760 and the second rotating body 770 (hereinafter also referred to as the "first pair").

[0122] In this way, according to the seismic source unit 75 of this embodiment, it is possible to generate vibrations with different frequencies by rotating the first and second sets via the transmitted portion 764 and the transmitted portion 784, which have different radii. This makes it possible to generate vibrations with a wider range of frequencies. As a result, the seismic source exploration system can generate vibrations that are more suitable for the target.

[0123] Furthermore, when the second group generates vibrations at a higher frequency than the first group, as in this embodiment, it is desirable for the weights in the second group to be lighter than the weights in the first group in order to generate equivalent vibrational energy over a wide frequency range.

[0124] Eighth embodiment Fig. 14 is a schematic diagram of the seismic source unit 80 according to the eighth embodiment. Fig. 14 shows the seismic source unit 80 as viewed in the horizontal direction (the X-axis direction in Fig. 14). As shown in Fig. 14, the seismic source unit 80 according to the eighth embodiment mainly includes a motor 800, a transmission unit 810, a first rotating body 820a, a second rotating body 820b, a third rotating body 820c, a fourth rotating body 820d, and bearings 812, 814, and 816.

[0125] The motor 800 has a main body 802 and a rotating shaft 804. The rotating shaft 804 is partially housed in the main body 802, extends in the Z-axis direction, and is configured to be rotatable about its length.

[0126] The transmission part 810 has a cylindrical shape extending in the Z-axis direction, and is provided on the opposite side of the rotation shaft 804 to the main body 802 so as to be rotatable integrally with the rotation shaft 804 .

[0127] First rotating body 820a, second rotating body 820b, third rotating body 820c, and fourth rotating body 820d are provided around transmission unit 810 in this order from the one closest to motor 800 so as to be rotatable integrally with transmission unit 810. First rotating body 820a, second rotating body 820b, third rotating body 820c, and fourth rotating body 820d all have substantially the same configuration.

[0128] Moreover, the bearing 812 is provided around the transmission unit 810 on the motor 800 side of the first rotor 820a so as to rotatably support the transmission unit 810. Moreover, the bearing 814 is provided around the transmission unit 810 on the opposite side of the motor 800 from the fourth rotor 820d so as to rotatably support the transmission unit 810. Furthermore, the bearing 816 rotatably supports the transmission unit 810 around the transmission unit 810 between the second rotor 820b and the third rotor 820c. Although three bearings are shown in FIG. 14, the number of bearings may be two or less, or four or more. The more the number of bearings, the more stable the rotation of the first to fourth rotors 820a to 820d, and the less the wear of the bearings, which is advantageous for long-term operation.

[0129] The first rotating body 820a has a weight support portion 822a and a weight 824a, the second rotating body 820b has a weight support portion 822b and a weight 824b, the third rotating body 820c has a weight support portion 822c and a weight 824c, and the fourth rotating body 820d has a weight support portion 822d and a weight 824d. The weight support portion 822 is disk-shaped and is provided around the transmission portion 810. A weight 824 is provided on a part of the circumference of the weight support portion 822. In this embodiment, when viewed in the Z-axis direction, the weights 824a to 824d are all disposed at the same position, and their positional relationship does not change even when the weight support portion 822 rotates.

[0130] When the motor 800 is driven, the rotating shaft 804 rotates. With the rotation of the rotating shaft 804, the transmission unit 810 rotates around the rotating shaft 804 in the direction shown by the arrow in FIG. 14. With this rotation, the first rotating body 820a, the second rotating body 820b, the third rotating body 820c, and the fourth rotating body 820d rotate around the rotating shaft 804. At this time, the weights 824a to 824d all rotate in the same phase. Therefore, the forces generated by the rotation of the weights 824a to 824d reinforce each other. Therefore, according to the seismic source unit 80 according to this embodiment, it is possible to generate vibrations that rotate in a horizontal plane.

[0131] The vibration generated by the seismic source section 80 according to the eighth embodiment has two horizontal components perpendicular to each other, unlike the seismic source section 70 according to the sixth embodiment. Therefore, the seismic source unit according to the eighth embodiment may have two receivers arranged perpendicular to each other so that the two horizontal components of the vibration can be detected.

[0132] According to the above embodiments, the seismic source section 130 according to the first embodiment can generate vibrations in the vertical direction, the seismic source section 70 according to the sixth embodiment can generate vibrations in one direction on a horizontal plane, and the seismic source section 80 according to the eighth embodiment can generate vibrations in a direction rotating within the horizontal plane. Therefore, by taking the seismic source unit out onto the ground as necessary and changing the configuration of the seismic source section, the direction of the component of the generated vibration can be changed to a desired condition.

[0133] Ninth embodiment 15 is a perspective view of the seismic source unit 90 according to the ninth embodiment. The seismic source unit 90 according to this embodiment is placed on the ground surface 98. The seismic source unit 90 according to the ninth embodiment includes a housing portion 92 (coupler), a seismic source device 94, and a weight 96.

[0134] The accommodation unit 92 has an internal space having an opening 922 formed by a cylindrical hole 920, and the seismic source device 94 is disposed in the internal space. The accommodation unit 92 may be formed of, for example, concrete. A weight 96 is disposed on the upper surface of the accommodation unit 92 for connecting the accommodation unit 92 to the ground surface 98. The weight of the weight 96 presses the accommodation unit 92 against the ground surface 98, thereby connecting the accommodation unit 92 to the ground surface 98. This makes it easier for the vibrations generated by the seismic source device 94 to be transmitted to the ground. If the vibrations of the seismic source device are large, the weight 96 may be increased.

[0135] The seismic source device 94 may have the seismic source unit described in the above embodiment. In this case, the direction corresponding to the Z axis is the horizontal direction. Therefore, when the seismic source unit 130 shown in the first embodiment shown in FIG. 5 is used, horizontal vibrations can be generated. Also, when the seismic source unit 70 according to the sixth embodiment shown in FIG. 12 is arranged so that the direction corresponding to the Y axis direction is the vertical direction, vertical vibrations can be generated. Since the seismic source device 94 is arranged in the internal space so as to be detachable from the opening 922 of the internal space, the seismic source device 94 can be removed from the storage unit 92 as necessary. This makes it possible to perform seismic exploration using vibrations under new conditions by changing the components of the seismic source unit (for example, gears, motors, and weights) and storing the seismic source device in the storage unit 92 again.

[0136] (supplement) The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0137] 1,2,3,4 Seismic exploration system, 10,94 Seismic source device, 12,14,16,18,19,90 Seismic source unit, 20,26 Signal acquisition device, 20,22,24 Receiver, 30,32,34,36 Management device, 37 Laser device, 42,44,46,48,49 Hole, 62,140 Coupling mechanism, 70,80 Seismic source unit, 92,100 Storage unit, 120 Support, 130 Seismic source unit, 160 Motor, 170 First rotating body, 180 Second rotating body, 260 Optical fiber, 370 Light source, 372 Acquisition unit

Claims

1. a vibration generating step in which a seismic source device disposed underground generates vibrations; an acquisition step of acquiring, by a signal acquisition device, a vibration signal based on the vibration generated by the seismic source device; The seismic source device includes an eccentric rotating body that rotates around a rotation axis, and a driving unit that generates the vibrations by rotating the rotating body. Seismic exploration methods.

2. The seismic source device is disposed in a hole formed in the ground. The seismic exploration method according to claim 1 .

3. The seismic source device is disposed at a position deeper than the aquifer. The seismic exploration method according to claim 2.

4. A plurality of the seismic source devices are arranged in the hole, The plurality of seismic source devices are arranged in a direction in which the hole extends. The seismic exploration method according to claim 2.

5. The seismic source device further includes a housing that houses the rotor and the drive unit, and a coupling mechanism that couples the housing to the inner surface of the hole. The seismic exploration method according to claim 2.

6. The signal acquisition device has a geophone that acquires the vibration signal, When a hole in which the seismic source device is disposed is defined as a first hole, the geophone is disposed in a second hole formed in the ground that is different from the first hole. The seismic exploration method according to claim 2.

7. The signal acquisition device includes an optical fiber arranged in the hole along an extension direction of the hole, a light source that propagates laser light through the optical fiber, and an acquisition unit that acquires the vibration signal based on the propagated laser light. The seismic exploration method according to claim 2.

8. The rotation axis is horizontal. The seismic exploration method according to claim 1 .

9. The seismic exploration method according to any one of claims 1 to 8, Subsurface monitoring methods.

10. A seismic source device that generates vibrations is placed underground, a signal acquisition device that acquires a vibration signal based on the vibration generated by the seismic source device, The seismic source device has an eccentric rotating body that rotates around a rotation axis, and a driving unit that generates the vibrations by rotating the rotating body. Seismic exploration system.

11. a seismic source unit having an eccentric rotating body that rotates around a rotation axis and a drive unit that generates vibrations by rotating the rotating body; a housing unit that houses the seismic source unit in an internal space, The storage section stores the seismic source section so that the seismic source section can be detached through an opening of the internal space. Epicenter device.

12. The seismic source device is disposed underground, The rotation axis is horizontal. The seismic source device according to claim 11.

13. the seismic source unit further includes an eccentric second rotor that rotates around a second rotation axis when the rotor is a first rotor and the rotation axis is a first rotation axis, the driving unit rotates each of the first rotating body and the second rotating body so that the first rotating body and the second rotating body generate vibrations of different frequencies. The seismic source device according to claim 11.

14. The seismic source device is disposed in a hole formed in the ground, and further includes a coupling mechanism for coupling an inner surface of the hole with the housing portion. The seismic source device according to claim 11.

15. The storage unit includes a pressure-resistant container. The seismic source device according to claim 11.

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