JP7082643B2 - Underwater tremor exploration device - Google Patents

Description

The present invention relates to a technique for performing a tremor array exploration on the bottom of a water such as the bottom of a sea or a lake.

The present inventors have proposed an exploration method for easily investigating the S-wave velocity structure of the ground at a depth of 100 m or less or 200 m or less from the seafloor as a seafloor tremor array exploration (Non-Patent Document 1 and Patent Documents below). 1). In this method, four independent seismographs (microtremometers) are arranged in a triangular array to observe microtremors, and the obtained microtremor data is analyzed to obtain the S-wave velocity structure of the ground.

Here, the ground depth that can be explored is about 0.4 to 1.6 times the base length of the array. For example, when the base length of the array is 50 m, the S wave velocity structure of the ground at a depth of about 20 m to 80 m below the seabed can be obtained.

In order to install a microtremor in this technique, a work ship is guided by GPS, and when it reaches a predetermined position, it is dropped from the ship and landed on the ground. Even if the ground is surveyed at a depth of 30 m or less, in the case of such an installation method, the installation with an accuracy of 5 m or less from the target point is the limit.

When carrying out a fine movement array exploration, the error in the relative position between the fine movement meters is required to be 10% or less of the array base length. Assuming that the error at the time of installation is 5 m, this installation method cannot be used for exploration with a base length of 50 m or less. Assuming that the base length is 50 m, the ground depth that can be explored is about 50 m × 0.4 = 20 m at the shallowest. Therefore, with this method, it is difficult to accurately obtain an S-wave velocity structure shallower than 10 m below the seafloor and shallower than 20 m depending on the noise situation. That is, in the above-mentioned technique, there is room for improvement in the measurement accuracy of the S wave velocity structure at a shallow depth.

Further, in Non-Patent Document 2 below, an analysis method called the CCA method is proposed. According to this method, by arranging a plurality of microtremors in an array in a narrow range on the ground surface, the S wave velocity structure of the ground can be measured with high accuracy.

However, in this method, it is necessary to accurately set the positional relationship between the microtremors. Therefore, it was difficult to use this method for measuring seafloor tremors.

Japanese Unexamined Patent Publication No. 2020-79716

Mikihiro Imai, Ikuzo Miyazaki, Dai Nobuoka, Yoshikazu Matsubara, Aya Hiraide (2019) "Application of Geophysical Exploration to Offshore Geotechnical Investigation: Submarine Microtremor Array Exploration", Proceedings of the SEGJ Conference 140, 27-30, Geophysical Exploration Society Ikuo Naga, Taku Tada, Yuzo Shinozaki (2008) "New microtremor exploration method using ultra-small array: simple estimation of shallow ground average S wave velocity", Geophysical Exploration, 61, 457-468.

The present invention has been made in view of the above circumstances. A main object of the present invention is to provide a technique capable of accurately obtaining an S wave velocity structure at a shallow depth on a water bottom such as the sea floor.

The present invention can be expressed as the invention described in the following items.

(Item 1)
An exploration device used for microtremor array exploration on the bottom of the water.
It is equipped with multiple fine movement meters, a main body, and a support.
The plurality of microtremors are configured to detect and output the microtremors of the bottom of the water when they are installed on the bottom of the water.
The main body unit includes a recording unit that records the outputs of the plurality of fine movement meters.
The support is configured to support the plurality of fine movement meters so that the distance between the plurality of fine movement meters is maintained.
In addition, the support is a submersible microtremor exploration device configured to block vibration transmission from one of the plurality of microtremors to the other.

(Item 2)
The support includes a frame and a connection portion.
The frame is configured in an annular shape.
The submersible microtremor exploration device according to item 1, wherein the connecting portion is configured to connect the frame and the plurality of microtremors so as to block mutual vibration transmission.

(Item 3)
The plurality of fine movement meters have first to fourth fine movement meters.
The first to third microtremors are arranged at equal intervals with each other inside the frame.
The fourth fine movement meter is arranged at the position of the center of gravity of the first to third fine movement meters.
The connection portion connects the first to third microtremors to the frame so as to block mutual vibration transmission.
Further, the water bottom tremor exploration device according to item 2, wherein the connection portion connects the fourth tremor meter to the first to third tremors so as to block mutual vibration transmission.

(Item 4)
The connection portion is made of a chain or rubber, whereby the plurality of fine movement meters and the frame can move slightly from each other while maintaining the required relative position accuracy. The water bottom tremor exploration device according to item 3.

(Item 5)
The main body further includes a closed container and a battery.
The battery is configured to supply electric power to the recording unit.
The closed container houses the recording unit and the battery.
The underwater microtremor exploration device according to any one of items 1 to 4, wherein the closed container is attached to the support and is put into water together with the plurality of microtremors.

(Item 6)
The support includes a substantially rod-shaped rubber member that connects the plurality of fine movement meters.
Item 2. The water bottom according to item 1, wherein the rubber member has a damping ability to attenuate a vibration transmitted from any of the plurality of tremors and has a shape-retaining property capable of maintaining an interval between the plurality of tremors. Microtremor exploration device.

(Item 7)
It is a water bottom tremor exploration method using the water bottom tremor exploration apparatus according to any one of items 1 to 6.
A step of arranging the fine movement meter on the bottom of the water by putting the plurality of fine movement meters into water together with the support.
A step of recording vibration data detected by the plurality of microtremors in the recording unit, and
A bottom tremor exploration method including a step of exploring the state of the ground at the bottom of the water using the vibration data recorded in the recording unit.

(Item 8)
Further, it is provided with a step of vibrating the surface of the water bottom.
Item 7. The water bottom tremor exploration method according to item 7, wherein the step of recording the vibration data in the recording unit is performed substantially at the same time as the vibration.

According to the water bottom tremor exploration device of the present invention, since the positional relationship between the tremors can be maintained by the support, a plurality of tremors can be accurately arranged in an array even in a narrow range on the water bottom. be able to. Moreover, in this device, it is possible to reduce the possibility that noise from other fine movement meters is mixed in through the support. Therefore, according to this device, it is possible to estimate the S wave velocity structure at a shallow depth at the bottom of the water relatively accurately.

It is a schematic explanatory drawing in the state which the water bottom fine movement exploration apparatus which concerns on 1st Embodiment of this invention is arranged underwater. It is an enlarged view of the main part in the water bottom microtremor exploration apparatus of FIG. It is explanatory drawing which enlarges and shows the part of the buoy in the water bottom fine movement exploration apparatus of FIG. It is a block diagram of the main body part in the water bottom microtremor exploration apparatus of FIG. It is explanatory drawing for demonstrating the procedure of performing exploration using the water bottom tremor exploration apparatus of FIG. It is a block diagram of the main body part used in the water bottom fine movement exploration apparatus which concerns on 2nd Embodiment of this invention. It is a schematic explanatory drawing in the state which the water bottom fine movement exploration apparatus which concerns on 3rd Embodiment of this invention is arranged underwater. It is explanatory drawing for demonstrating the procedure at the time of installing the water bottom fine movement exploration apparatus of FIG. It is explanatory drawing for demonstrating the procedure at the time of installing the water bottom fine movement exploration apparatus of FIG. It is explanatory drawing for demonstrating the procedure at the time of installing the water bottom fine movement exploration apparatus of FIG.

The water bottom tremor exploration apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

(Structure of this embodiment)
The water bottom tremor exploration device (hereinafter, may be simply abbreviated as "exploration device" or "device") 1 of the present embodiment is used for tremor array exploration on the water bottom. In the following description, it is assumed that this device 1 is used in the sea, but it is possible to use it in a place other than the sea such as a lake or a river.

This device 1 includes a plurality of fine movement meters 2, a main body portion 3, and a support 4 (see FIG. 1). The device also includes a buoy 5 and a cable 6 as additional configurations.

(Microtremor)
The plurality of fine movement meters 2 are configured to detect and output fine movements of the seabed 200 in a state of being installed on the seabed (water bottom) 200 (see FIG. 1).

The plurality of fine movement meters 2 in the present embodiment are composed of the first to fourth fine movement meters 21 to 24 (see FIG. 2). The first to third tremors 21 to 23 are arranged inside the frame 41, which will be described later, at equal intervals from each other and in a triangular shape. The signals (signals indicating fine movements) from the first to third fine movement meters 21 to 23 are aggregated and transmitted to the cable 6 via the signal line 25. The fourth fine movement meter 24 is arranged at the position of the center of gravity of the first to third fine movement meters 21 to 23 (see FIG. 2). The signal from the fourth fine movement meter 24 is also aggregated and transmitted on the cable 6.

(Main body)
The main body 3 of the present embodiment includes a recording unit 31, a GPS signal receiving unit 32, a battery 33, and a closed container 34 (see FIG. 4). The main body 3 of the present embodiment is attached to the buoy 5, so that the main body 3 can be arranged in the vicinity of the water surface 100. Specifically, the main body 3 is attached to the tip of the buoy main body 51, which will be described later (see FIG. 3).

The recording unit 31 includes an amplifier 311 that amplifies the signal transmitted via the cable 6, an A / D converter 312 that A / D converts the amplified signal, and a recording medium 313 that records the converted signal. have.

The GPS signal receiving unit 32 is configured to receive a GPS signal transmitted from a GPS satellite 300 (see FIG. 1), and specifically is configured to include a GPS antenna. In the present embodiment, GPS data (for example, time data and position data) recorded by the GPS signal receiving unit 32 can also be recorded on the recording medium 313 of the recording unit 31. With this configuration, the GPS signal receiving unit 32 of the present embodiment receives the time information and / or the position information included in the GPS signal and records them in the recording unit 31.

The battery 33 is configured to supply electric power for driving an operating portion of the main body 3, for example, a recording unit 31. Since a recording time of about several hours is sufficient for general seafloor tremor array exploration, the battery 33 has a capacity corresponding to that, for example, a drive time of 10 hours or more, more preferably 50 hours or more. Is used.

With this configuration, the main body 3 of the present embodiment can record the outputs of the plurality of fine movement meters 2 in the recording unit 31.

The closed container 34 is configured in a box shape so as to be watertight inside (see FIG. 3). Inside the closed container 34, the main components of the main body 3, for example, the recording unit 31, the GPS signal receiving unit 32, and the battery 33 are housed. As the closed container 34, a pressure-resistant container that can be used even at a certain depth can be used, if necessary, but when it is attached to the buoy 5 and used, it has a pressure resistance sufficient to be used on the seabed 200. It doesn't have to be.

(Support)
The support 4 of the present embodiment includes a frame 41 and a connecting portion 42 (see FIGS. 1 and 2). The frame 41 is configured in an annular shape. Specifically, the frame 41 of the present embodiment has a substantially hexagonal shape, but is not limited to this, and may be, for example, a circular shape or another polygonal shape. The frame 41 is configured to be substantially parallel to the surface of the seabed 200 when it is installed on the seabed 200.

The connecting portion 42 connects the first to third microtremors 21 to 23 to the frame 41 so as to block mutual vibration transmission. Further, the connecting portion 42 connects the fourth fine movement meter 24 to the first to third fine movement meters 21 to 23 so as to cut off mutual vibration transmission. As a result, the connecting portion 42 is configured to connect the frame 41 and the plurality of fine movement meters 2 so as to cut off mutual vibration transmission.

More specifically, the connecting portion 42 of the present embodiment includes the first to sixth connecting tools 421 to 426 (see FIG. 2). The first to third connectors 421 to 423 connect the frame 41 and the first to third fine movement meters 21 to 23, and the fourth to sixth connectors 424 to 426 are the first to 426. The third tremor meters 21 to 23 and the fourth tremor meter 24 arranged inside them (center of gravity position) are connected.

The first to sixth connecting tools 421 to 426 constituting the connecting portion 42 of the present embodiment are all made of a chain or rubber. As a result, the plurality of fine movement meters 2 and the frame 41 can move slightly with each other while maintaining the required relative position accuracy.

With the above configuration, the support 4 is configured to support the plurality of fine movement meters 2 so that the distance between the plurality of fine movement meters 2 is maintained. Further, with this configuration, the support 4 of the present embodiment is configured to block the vibration transmission from one of the plurality of fine movement meters 2 to the other.

(buoy)
The buoy 5 includes a buoy body 51 that can float on the water surface 100 (see FIG. 1) and a hook 52 for attaching the cable 6 to the buoy body 51 (see FIG. 3). The buoy body 51 preferably has a buoyancy sufficient to allow the body 3 attached to the buoy body 51 to float on the surface of the water. As such a buoy main body 51, an existing one can be used, and further detailed description thereof will be omitted. The hook 52 preferably has a configuration in which the cable 6 can be easily attached to and detached from the buoy body 51. As for the hook 52, an existing one can be used, so detailed description thereof will be omitted.

(cable)
The cable 6 is adapted to collectively transmit the signals from all the fine movement meters 2 to the recording unit 31 of the main body unit 3. As such a cable 6, for example, a cable in which a plurality of signal lines (not shown) corresponding to the individual fine movement meters 2 are twisted and the necessary coating is applied to the outside can be used. It is desirable that the signals transmitted by the cable 6 are transmitted separately for each tremor meter. The cable 6 of the present embodiment also has a function of connecting the buoy 5 to the fine movement meter 2 (or the main body portion 3), and has the necessary elasticity and mechanical strength.

The cable 6 of the present embodiment passes through the closed container 34 and is connected to the recording unit 31 by using a means that does not impair the watertightness of the closed container 34, for example, a sealing member (not shown).

(Water bottom tremor exploration method of this embodiment)
Next, with reference to FIG. 5, an example of a method for exploring the tremor of the seabed 200 using the above-mentioned device 1 will be described.

(Step SA-1 in FIG. 5)
In this example, it is assumed that the device 1 is mounted on a ship having equipment (not shown) capable of receiving GPS signals. In this state, the position where the main body 3 of the device 1 should be dropped is determined based on the GPS signal.

(Step SA-2 in FIG. 5)
When the ship reaches a predetermined position, the fine movement meter 2 and the support 4 are dropped into the water while the cable 6 is unwound. Then, the fine tremor 2 and the support 4 descend due to their own weight and reach the seabed 200 (see FIG. 1). As shown in FIG. 1, in the landed state, the frame 41 of the support 4 is arranged on the seabed 200 in a substantially horizontal state. In this state, each tremor meter 2 can come into contact with the seabed 200 and detect the vibration of the seabed 200 while maintaining the mutual positional relationship. At this time, the upper portion of the buoy 5 is arranged above the sea level 100 (see FIG. 1), whereby the main body portion 3 is also arranged at a position higher than the sea level 100. Here, the length of the cable 6 is sufficiently longer than the water depth assumed in advance so that the buoy 5 is not submerged.

(Step SA-3 in FIG. 5)
The fine movement meter 2 installed on the seabed 200 receives the fine movement on the surface of the seabed 200, and the fine movement is recorded in the recording unit 31 of the main body 3 via the signal line 25 and the cable 6. Further, the GPS signal receiving unit 32 of the main body unit 3 receives the GPS signal from the GPS satellite 300. In the present embodiment, the vibration recording time can be accurately grasped by using the time information included in the GPS signal. In this embodiment, since each signal can be simultaneously recorded in multiple channels by the recording unit 31, it is possible to synchronize between the fine movement meters 2 without using a GPS signal.

(Step SA-4 in FIG. 5)
After a predetermined time (for example, 1 hour to 2 hours or more) has elapsed, the cable 6 is pulled up to collect the entire device 1 including the fine movement meter 2. This recovery can be performed relatively easily by using a ship by using the position of the buoy 5 as a mark.

(Step SA-5 in FIG. 5)
Then, by analyzing the vibration data recorded in the main body 3 of the recovered device 1, the state of the ground, for example, the S wave velocity structure can be estimated. As a method for analyzing the S wave velocity structure, the method described in Non-Patent Document 2 (CCA method) can be used, and therefore detailed description thereof will be omitted.

In the present embodiment, the support 4 enables the plurality of fine movement meters 2 to be accurately positioned on the seabed 200. If the plurality of fine movement meters 2 are accurately positioned, the depth is measured by using the method described in Non-Patent Document 2, for example, in a measurement using an array having a base length L (see FIGS. 1 and 2) of about 50 cm. It is possible to accurately obtain an S velocity structure shallower than 30 m (for example, a depth of about 5 to 30 m underground).

Further, in the present embodiment, since the support 4 is configured to block the vibration transmission from one of the plurality of fine movement meters 2 to the other, it is possible to suppress the mixing of noise in the fine movement meter 2 to a low level. From this point as well, the measurement accuracy can be improved.

That is, the exploration device 1 of the present embodiment accurately maintains the positional relationship between the microtremors 2 and cuts off the vibration transmission between the microtremors 2 to obtain a shallow S wave in the seafloor ground. There is an advantage that the velocity structure can be obtained accurately.

Here, in the present embodiment, "cutting off vibration transmission" means that vibration is attenuated to such an extent that it does not substantially cause any trouble.

Further, according to the apparatus 1 of the present embodiment, the size (array size) of the support 4 including the fine movement meter 2 can be reduced. In other words, in this embodiment, since the entire device can be miniaturized, it is possible to improve the efficiency of work such as transporting the device, putting it on the seabed, and then collecting it, and it is possible to reduce the actual operating cost. There are also advantages.

Further, the exploration in the present embodiment can be performed at the same point as the exploration by the method of Non-Patent Document 1 described above, for example. By doing so, it is possible to connect the S wave velocity structure at a large depth obtained by the method of Non-Patent Document 1 and the S wave velocity structure at a shallow depth obtained by the method of the present embodiment. As a result, there is an advantage that the S wave velocity structure of the ground can be captured in a wide range from shallow depth to large depth.

Further, in the method of Non-Patent Document 1 described above, since the cable is extended from each fine movement meter to the water surface, the cable length becomes long in the case of a large water depth. For example, the depth of the seabed explored for the installation of floating offshore wind turbines is said to be about 100m to 150m. In this case, since the cable length is also about the same, it is possible that the devices may be damaged due to the entanglement of the cables. On the other hand, in the present embodiment, since the support 4 to the water surface 100 are connected by one cable 6, such a problem can be avoided. Therefore, according to the device 1 of the present embodiment, there is an advantage that the entanglement of the cables can be prevented and the device can be prevented from being damaged even in the microtremor exploration work at a deep water depth.

If the energy of the high-frequency component of the tremor in the sea area to be investigated is not sufficient, a high-frequency vibration is artificially generated separately at an arbitrary point near the seabed where the tremor meter 2 is installed, and the observation record at that time is recorded. By performing the analysis using it, it is possible to make up for the shortage of high frequency components. Examples of the vibration generator (not shown) for that purpose include a sparker or an air gun used in sonic exploration, but the vibration generator is not limited thereto. If tremors including relatively high frequencies can be observed, it will be easy to obtain the S wave velocity in the shallow layer below the seafloor. Here, in geophysical exploration such as surface wave exploration and reflection method exploration, the relative positional relationship between the vibration point and the vibration receiving point is an extremely important parameter, but in the case of microtremor array exploration, the vibration point is the vibration receiving point. Relative positional relationships do not matter unless they are in the immediate vicinity (Reference: Chisato Konishi, Haruhiko Suzuki, Masaru Sato, Ei Liu, Toru Suzuki (2018): Evaluation of applicability of 3D constant tremor tomography to shallow areas, geophysical exploration Proceedings of the 139th Academic Lectures, 199-122). Therefore, in the embodiment of the present embodiment, the installation position accuracy of the vibration exciter does not have to be high.

It is also possible to use the device 1 of the present embodiment as one seismograph in Non-Patent Document 1 and perform conventional fine movement array exploration using a plurality of devices 1.

Further, it is also possible to apply a gimbal mechanism to each tremor meter 2 so that the tremor meter 2 maintains a horizontal position on the seabed 200.

The water bottom tremor exploration method using the device 1 of the present embodiment can be expressed as follows:
A step of arranging the fine movement meter 2 on the seabed 200 by putting a plurality of fine movement meters 2 into the water together with the support 4.
A step of recording the vibration data detected by the plurality of microtremors 2 in the recording unit 31 and
A bottom tremor exploration method including a step of exploring the state of the ground on the seabed 200 using the vibration data recorded in the recording unit 31.

Further, this waterfloor tremor exploration method can include a step of vibrating the surface of the seafloor 200, in which case the step of recording vibration data in the recording unit 31 is substantially simultaneous with the vibration. Will be done.

(Second Embodiment)
Next, the exploration apparatus 1 according to the second embodiment of the present invention will be described with reference to FIG. In the description of the second embodiment, the same reference numerals are used for the elements that are basically common to the first embodiment described above to simplify the description.

In the first embodiment described above, the main body 3 is attached to the buoy 5, and the signal from each fine movement meter 2 is sent to the main body 3 via the cable 6. On the other hand, in this second embodiment, the main body 3 is attached to the support 4 or any of the fine movement meters 2. Further, in this second embodiment, the GPS signal receiving unit 32 is omitted. Further, the closed container 34 in this embodiment has a structure that can withstand the water pressure at the installed water depth. Further, instead of the cable 6 of the present embodiment, a connecting tool (not shown) such as a wire or a chain for connecting the buoy 5 and the support 4 is used. Here, the signal from each fine movement meter 2 can be recorded in the recording unit 31 via the signal line 25.

In this second embodiment, the main body 3 is thrown into the sea together with the support 4. In the present embodiment, all the signals of the fine movement meter 2 can be recorded in the recording unit 31 of the main body unit 3 in the sea. Here, in the present embodiment, since the signals of the fine movement meters 2 are simultaneously recorded in the recording unit 31, the time between the received signals can be synchronized without using the GPS signal. Therefore, after collecting the main body 3, the S wave velocity structure can be estimated using the signal recorded in the recording unit 31.

In the device 1 of the second embodiment, since the main body 3 is installed in the sea, the GPS signal cannot be received by the main body 3. Therefore, in the present embodiment, the GPS signal receiving unit 32 is omitted. Further, in this embodiment, it is not necessary to extend the cable 6 to the sea. As described above, in the second embodiment, the configuration of the device 1 can be simplified, so that the device cost can be reduced.

Since the other configurations and advantages in the second embodiment are basically the same as those in the first embodiment described above, further detailed description thereof will be omitted.

(Third Embodiment)
Next, the exploration apparatus 1 according to the third embodiment of the present invention will be described with reference to FIG. 7. In the description of the third embodiment, the same reference numerals are used for the elements that are basically common to the first embodiment described above to simplify the description.

In the first embodiment described above, the support 4 is composed of the frame 41 and the connecting portion 42. On the other hand, in the third embodiment, the support 4 is composed of a plurality of rubber members 44. These rubber members 44 connect a plurality of fine movement meters 2 to each other and are configured in a substantially rod shape.

The rubber member 44 has a damping ability that sufficiently damps the vibration (elastic wave) transmitted from the fine movement meter 2, and also has a shape-retaining property that can maintain an interval between the plurality of fine movement meters 2. Here, as the shape-retaining property of the rubber member 44, it is particularly preferable that the distance between the fine movement meters 2 can be maintained without expanding and contracting. As such a rubber member 44, for example, silicone rubber and chloroprene rubber can be used, but the rubber member 44 is not limited to these, and various rubbers having desired characteristics can be used.

An example of the procedure for throwing the device 1 into the sea according to the third embodiment will be described with reference to FIGS. 8 to 10. In this example, a hoisting rope is used as the cable 6. First, FIG. 8 shows a state before loading (for example, a state of being placed on a ship). Here, a desired weight 7 is attached to the cable 6.

Then, the rope 8 for loading is passed through the first to third fine movement meters 21 to 23, and these fine movement meters 21 to 23 are lifted by an appropriate method (crane, chain block, etc.) through the rope 8. (See FIG. 9). In this state, since the rubber member 44 is curved, the first to third fine movement meters 21 to 23 are gathered together.

In this state, the support 4 is suspended from the seabed 200 at a predetermined position. After arriving at the seabed 200, if the rope 8 is pulled up, each tremor meter 2 descends by its own weight and is placed at an appropriate position (see FIG. 7).

After the fine movement measurement is completed, the fine movement meter 2 can be recovered together with the support 4 by pulling up the cable 6 (see FIG. 10).

Since the other configurations and advantages in the third embodiment are basically the same as those in the first embodiment described above, further detailed description thereof will be omitted.

It should be noted that the description of the embodiment is merely an example, and does not show the configuration essential to the present invention. The configuration of each part is not limited to the above as long as the gist of the present invention can be achieved.

For example, in the above description, the seabed is mainly assumed as the seabed, but the above-mentioned device can be used not only on the seabed but also on the lake bottom or riverbed.

1 Submersible microtremor probe 2 Microtremor 21-24 1st to 4th microtremor 25 Signal line 3 Main unit 31 Recording unit 311 Amplifier 312 A / D converter 313 Recording medium 32 GPS signal receiver 33 Battery 34 Sealed container 4 Support Body 41 Frame 42 Connection 44 Rubber member 5 Buoy 51 Buoy body 52 Hook 6 Cable 7 Weight 8 Input rope 100 Water surface (sea surface)
200 Underwater (seabed)
300 GPS satellites

Claims (4)

An exploration device used for microtremor array exploration on the bottom of the water.
It is equipped with multiple fine movement meters, a main body, and a support.
The plurality of microtremors are configured to detect and output the microtremors of the bottom of the water when they are installed on the bottom of the water.
The main body unit includes a recording unit that records the outputs of the plurality of fine movement meters.
The support is configured to support the plurality of fine movement meters so that the distance between the plurality of fine movement meters is maintained.
Moreover, the support is configured to block the vibration transmission from one of the plurality of fine movement meters to the other.
The plurality of fine movement meters have first to fourth fine movement meters.
The support is radially arranged between the fourth tremor and the first to third tremors to connect the fourth tremor to the first to third tremors. It has a connection portion that maintains the interval and blocks mutual vibration transmission between the fourth tremor meter and the first to third tremor meters.
The connection portion is made of a chain or rubber, and is made of a chain or rubber .
When the connecting portion is the chain, the distance is provided by a frame arranged outside the first to third tremors and connected to the first to third tremors by another chain or rubber. A submersible microtremor exploration device that is designed to be held . The main body further includes a closed container and a battery.
The battery is configured to supply electric power to the recording unit.
The closed container houses the recording unit and the battery.
The underwater microtremor exploration device according to claim 1, wherein the closed container is attached to the support and is put into water together with the plurality of microtremors. A method for exploring a bottom tremor using the tremor exploration apparatus according to claim 1 or 2.
A step of arranging the fine movement meter on the bottom of the water by putting the plurality of fine movement meters into water together with the support.
A step of recording vibration data detected by the plurality of microtremors in the recording unit, and
A bottom tremor exploration method including a step of exploring the state of the ground at the bottom of the water using the vibration data recorded in the recording unit. Further, it is provided with a step of vibrating the surface of the water bottom.
The underwater tremor exploration method according to claim 3, wherein the step of recording the vibration data in the recording unit is performed substantially at the same time as the vibration.

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