JP2023037548A - Seismic source unit and seafloor geological survey system - Google Patents

Abstract

[Problem] To provide a seismic source unit and seabed geological exploration system that realizes simplified calculation processing during analysis and improved exploration accuracy. [Solution] A seismic source unit equipped with a seismic source that emits sound waves to cause multiple receivers of a streamer cable towed by a ship to acquire reflected waves. The seismic source unit has a rod-shaped support member that is attached to a central location in the fore-aft direction of the ship's side, and a seismic source device that includes a seismic source and is attached to one end of the support member. The seismic source device is placed in the sea during exploration. [Selected Figure] Figure 1

Description

TECHNICAL FIELD The present invention relates to a seismic source unit including a seismic source that oscillates sound waves and a seafloor geological exploration system.

2. Description of the Related Art A seafloor geological exploration system is known in which a plurality of geophones provided on a streamer cable towed by a ship receives reflected waves of sound waves emitted from a seismic source from the seafloor, stratum boundaries, and the like. Such a seafloor geological exploration system analyzes received reflected waves to explore geological structures, active fault distributions, and the like (for example, Patent Document 1).

In the seafloor geological survey system of Patent Document 1, a plurality of seismic sources are provided on an oscillation cable towed by a ship, and the composite wave received by the geophone of the streamer cable is separated into a plurality of reflected waves for analysis. It has become.

JP 2018-185206 A

However, in the method of towing the epicenter from the stern as in Patent Document 1, the position of the epicenter is not stable. The effect increases the noise component. In other words, the conventional configuration not only complicates the arithmetic processing at the time of analysis, but also causes a decrease in search accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems described above, and aims to provide a seismic source unit and a seafloor geological survey system that simplify arithmetic processing during analysis and improve exploration accuracy. do.

A seismic source unit according to an aspect of the present invention is a seismic source unit that includes a seismic source that oscillates sound waves for causing a plurality of geophones of a streamer cable towed by a ship to acquire reflected waves, It has a rod-shaped support member attached to a central location in the direction, and an epicenter device that includes an epicenter and is attached to one end of the support member.

A seafloor geological exploration system according to an aspect of the present invention includes the above-described epicenter unit, and a connecting member provided at a central location in the longitudinal direction of the shipboard and connecting a supporting member to the location.

According to the present invention, since the position of the seismic source device is stabilized by attaching the support member to the side, calculation processing considering the positional fluctuation of the seismic source becomes unnecessary, and the influence of air bubbles caused by the wake of the propeller etc. is reduced. be able to. Therefore, it is possible to simplify the arithmetic processing at the time of analysis and improve the search accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the whole structural example of the submarine geological survey system which concerns on Embodiment 1 of this invention. 1 is a schematic configuration diagram illustrating an overview of a seafloor geological exploration system according to Embodiment 1 of the present invention; FIG. FIG. 2 is a perspective view illustrating the depth retention member of FIG. 1; It is the perspective view which illustrated the focus unit of FIG.1 and FIG.2, and its peripheral structure. 2 is a block diagram illustrating the functional configuration of the search control device of FIG. 1; FIG. FIG. 11 is a perspective view illustrating a depth retention unit according to a modification of Embodiment 1 of the present invention; FIG. 8 is a perspective view illustrating a depth retention member according to Embodiment 2 of the present invention;

Embodiment 1.
An overall configuration example of a seafloor geological exploration system 100 according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. The seafloor geological survey system 100 detects elastic waves generated from the epicenter and reflected by the physical boundary under the seafloor with a streamer cable, converts the detected vibrations into electrical signals, and explores strata and geological structures under the seafloor. , which realizes so-called three-dimensional geophysical exploration.

As shown in FIG. 1 , the seafloor geological exploration system 100 has an epicenter unit 50 provided on at least one of the left and right sides of a ship 500 and a streamer cable 60 towed by the ship 500 . In Embodiment 1, the submarine geological exploration system 100 has two epicenter units 50, which are provided on the left and right sides of the vessel 500, respectively.

The focus unit 50 has a rod-shaped support member 51 attached to a central location in the longitudinal direction of the ship 500 and a focus device 52 attached to one end of the support member 51 . By fixing the focus device 52 to the ship 500, the position of the focus 52s is determined reliably. That is, since the position of the epicenter 52s is stabilized compared to the conventional method of towing the epicenter from the stern, it is possible to reduce the arithmetic processing during analysis and improve the accuracy of exploration. In addition, it is possible to reduce the effect of air bubbles caused by the propeller wake, etc., which causes noise.

The support member 51 is attached so as to be parallel to the vertical direction of the ship 500 . When collecting data for three-dimensional geophysical exploration (hereinafter also referred to as exploration), the focus device 52 is placed in the sea. Henceforth, the board in the ship 500 is also simply called "board." Details of the focus unit 50 will be described later. 1 and 2, a GNSS antenna 66 relating to a GNSS (Global Navigation Satellite System) is attached to each of the support member 51 of the epicenter unit 50 and the depth retention member 10 on the rear side. It is

The streamer cable 60 has a lead-in cable 61 with one end connected to the stern side of the ship 500, and an active cable 62 connected to the other end of the lead-in cable 61 and provided with a plurality of geophones 62a. are doing. That is, the active cable 62 is a portion of the streamer cable 60 in which a plurality of geophones 62a are provided at predetermined intervals. The geophone 62a is composed of, for example, a hydrophone that converts changes in sound pressure into changes in voltage. In the active cable 62, the plurality of geophones 62a are arranged at intervals set based on the horizontal resolution or the like.

Here, as shown in FIG. 2, in the active cable 62 being towed by the ship 500, the direction from the end on the lead-in cable 61 side to the other end, that is, the central axis of the active cable 62 extends. The direction is called the axial direction. In the active cable 62, a plurality of geophones 62a are connected along the axial direction. Hereinafter, the end of the active cable 62 on the lead-in cable 61 side is also called the front end, and the other end is also called the rear end. Hereinafter, the axial direction of the active cable 62 is also simply referred to as "axial direction".

The submarine geological exploration system 100 has a depth holding member 10 that adjusts and holds the underwater depth of the active cable 62 of the streamer cable 60 . The submarine geological exploration system 100 of Embodiment 1 is provided with two depth retention members 10 for one streamer cable 60 . When two streamer cables 60 are towed by a vessel 500 as shown in FIG. Two depth retention members 10 corresponding to one streamer cable 60 are provided at both ends of the active cable 62 . Here, the front end portion of the active cable 62 is a predetermined portion from the front end of the geophone 62 a mounted on the frontmost side to the connection point with the lead-in cable 61 . The rear end portion of the active cable 62 is a predetermined portion from the rear end of the geophone 62a mounted on the rearmost side to the terminal end 62z. When the active cable 62 with the depth retention member 10 attached to each of its front and rear ends is thrown into the sea, the entire area of the active cable 62 sinks to the target depth.

The submarine geological exploration system 100 has a rope 64a that connects the stern of the ship 500 and the depth retention member 10 on the front side. The rope 64a is attached, for example, to the fixing member 22 at an intermediate position between the two floating bodies 21. As shown in FIG. The rope 64a may be connected to the front outer member 22a or the inner member 22b of the fixed member 22 . However, the rope 64a may be connected to the outer member 22a behind the fixed member 22. FIG. The submarine geological exploration system 100 also has a rope 64b that connects the active cable 62 and the depth retention member 10 on the rear side. The rope 64b is attached to the active cable 62 at a position between the depth retention member 10 on the front side and the depth retention member 10 on the rear side and at a position midway between the two floating bodies 21 on the fixed member 22 . The rope 64a may be connected to the front outer member 22a or the inner member 22b of the fixed member 22 . However, the rope 64b may be connected to the rear outer member 22a of the fixing member 22 . Here, the depth retention member 10 on the front side corresponds to the "first depth retention member", and the depth retention member 10 on the back side corresponds to the "second depth retention member". Further, the rope 64a corresponds to the "first rope", and the rope 64b corresponds to the "second rope".

As illustrated in FIG. 3, the depth retention member 10 has a floating body portion 20 having two floating bodies 21 having the same shape and a fixing member 22 to which the two floating bodies 21 are fixed with a space therebetween. ing. The depth retention member 10 also has a depth adjustment section 30 that is connected to the fixed member 22 at an intermediate position between the two floating bodies 21 and one end of which is connected to the active cable 62 . The length of the depth adjusting portion 30 from the joint with the fixing member 22 to one end is set based on the target depth of the active cable 62 . The target depth is set based on the positional relationship between the epicenter device 52 and the epicenter 52s, the water depth of the exploration area, and the like. In Embodiment 1, the target depth is set to about 1 m to 2 m, and the overall configuration of the depth retention member 10 is determined.

Here, the x-axis direction, the y-axis direction, and the z-axis direction are defined as shown in FIG. 3, and the streamer cable 60 is towed by the vessel 500 positioned on the positive side of the x-axis. Regarding the depth retention member 10, the x-axis direction is the front-back direction, the y-axis direction is the left-right direction, the z-axis direction is the up-down direction, and particularly the x-axis positive side is the front side. The x-axis direction corresponds to the axial direction of the active cable 62 . That is, the front-rear direction of the depth retention member 10 is parallel to the axial direction when attached to the active cable 62 .

Each floating body 21 has a shape extending in one direction, and is fixed to a fixing member 22 in a state of being aligned. That is, the two floating bodies 21 are fixed to the fixing member 22 so that their extending directions are parallel to the front-rear direction. In a broad sense, each floating body 21 is formed in an elliptical or elliptical shape in plan view. Each floating body 21 is preferably formed into a bow shape or a spherical shape at least at the front portion on the traveling direction side (front side). The two floating bodies 21 are arranged such that their side surfaces face each other straight. That is, the two floating bodies 21 are fixed to the fixing member 22 so that the positions in the front-rear direction, that is, the positions of the front ends and the rear ends are equal.

Each floating body 21 is made of, for example, fiber reinforced plastics (FRP). Each floating body 21 may be made of other resin such as ABS resin. Each floating body 21 may have a hollow structure, a dense structure as a whole, or a combination of a hollow structure and a dense structure.

The floating body 21 exemplified in FIG. 3 is formed so as to be substantially left-right symmetrical, and formed so as to be substantially front-rear symmetrical. The floating body 21 is formed so as to taper from the top to the bottom. More specifically, the floating body 21 is formed so that the cross-sectional area on the plane including the extending direction, that is, the xy plane, gradually decreases from the top to the bottom. That is, the floating body 21 is formed so that the width in the left-right direction gradually decreases from the top to the bottom.

In addition, the floating body 21 has a cross-sectional area (including a hollow portion in the case of a hollow structure) on a plane perpendicular to the stretching direction, that is, on the yz plane, from the center in the stretching direction to the x-axis positive side and the x-axis negative side. It is formed so that it becomes smaller gradually toward . That is, the floating body 21 is formed so that its front and rear sides are streamlined. Therefore, it is possible to reduce the followability and straightness of the ship 500 and the influence of waves. Moreover, since the generation of waves and bubbles can be suppressed, the noise component of the composite wave received by the geophone 62a can be reduced. Thus, the floating body part 20 has a catamaran shape including two connected floating bodies 21 . Therefore, the stability during towing is high and the wave-making resistance can be reduced, so the depth of the active cable 62 can be accurately maintained.

The fixing member 22 is composed of a plurality of assembly members and connecting tools such as bolts. The plurality of assembly members are composed of one or more rod-like members, or one or more plate-like members, or a combination thereof. FIG. 3 illustrates the fixing member 22 mainly composed of a rod-shaped member. The rod-shaped member that constitutes the fixing member 22 is preferably made of a relatively lightweight material such as an aluminum pipe or a vinyl chloride pipe. The same applies to the material of the plate-like member. At least the fixing member 22 has a pair of outer members 22a that are formed in a rod shape or plate shape and connect the two floating bodies 21 together. The pair of outer members 22a are arranged in parallel with a predetermined distance therebetween. The predetermined distance is set in advance in consideration of the speed of the vessel 500 during exploration, the shape and structure of the floating body 21, the stability when the active cable 62 is supported by the other end 31n, and the like. The fixed member 22 of FIG. 3 has an inner member 22b arranged parallel to and between a pair of outer members 22a. The shape, number, and arrangement of each assembly member in the fixing member 22, as well as the method of fixing the two floating bodies 21, are not limited to the example of FIG. 3, and various variations can be selected.

The depth adjustment unit 30 in Embodiment 1 has two rod-shaped adjustment members 31 . The length of the adjustment member 31 is set based on the target depth of the active cable 62 . Each adjustment member 31 has a rod-shaped portion 31a, one end portion 31m, and the other end portion 31n. Each adjusting member 31 has a length from the other end 31n to the one end 31m where it is connected to the fixing member 22 based on the target depth of the active cable 62 . That is, the one end portion of the depth adjustment portion 30 is configured by the one end portion 31m of one adjustment member 31 and the one end portion 31m of the other adjustment member 31 . FIG. 3 exemplifies an adjusting member 31 made of a relatively thick and heavy wire, and having one end 31m and the other end 31n formed by bending both ends into a ring shape and fixing them. there is The adjusting member 31 is made of carbon steel, for example.

Each adjustment member 31 is a bar-shaped member having the other end 32b connected to the fixing member 22 and extending from the other end 32b to the one end 32a. The two adjustment members 31 are connected to the fixed member 22 at a predetermined distance along the axial direction of the active cable 62, that is, so as to be aligned parallel to the axial direction. More specifically, the other end 31n of the front adjustment member 31 is connected to the front outer member 22a by a connector 41, and the other end 31n of the rear adjustment member 31 is connected to the rear by the connector 41. It is connected to the external member 22a.

One end 31m of each adjustment member 31 is attached to the active cable 62 by a connector 42 so as to be parallel to each other. Although FIG. 3 simply illustrates the structures of the coupler 41 and the coupler 42 , various well-known couplers such as shackles can be used as the coupler 41 and the coupler 42 .

Although FIG. 3 illustrates the adjusting member 31 made of one wire, the shape and the like of the adjusting member 31 are not limited to the example of FIG. For example, the adjustment member 31 may have one end portion 31m in which only the end portion disposed below the wire is bent into a ring shape and fixed. In other words, the adjustment member 31 may be one in which the other end portion is not processed at all. With this configuration, the one end 31m is heavier than the other end 31n, and the center of gravity is lowered, so that the depth of the active cable 62 can be more stably maintained. The adjusting member 31 may be configured by a single rod-shaped member such as the rod-shaped portion 31a.

Although FIG. 3 shows an example in which the depth adjustment unit 30 has two adjustment members 31, the depth adjustment unit 30 is not limited to this. The depth adjustment section 30 may be configured with one adjustment member 31 . However, from the viewpoint of stably supporting the active cable 62 , it is preferable that the depth adjustment section 30 has two adjustment members 31 . However, the depth adjustment section 30 may have three or more adjustment members.

The depth retention member 10 may have a weight (not shown) provided at the one end 31m of the adjusting member 31 or at the end of the rod-shaped portion 31a on the one end 31m side. In this case, the one end of the depth adjusting portion 30 corresponds to the one end 31m of the adjusting member 31 or the end of the rod-like portion 31a on the one end 31m side. As the weight, a material containing lead such as a lead sheet or a rod-shaped lead lump can be preferably used. For example, a lead sheet may be wound around one end 31m or rod-shaped portion 31a, and one or a plurality of rod-shaped lead lumps may be fixed to one end 31m or rod-shaped portion 31a with a binding band or the like. A two-part structure weight may be employed.

By the way, as shown in FIG. 3 , at the start of towing by the vessel 500 , a tension T caused by the towing of the streamer cable 60 acts on one end of the depth adjustment section 30 fixed to the active cable 62 . On the other hand, on the depth retention member 10, the drag D caused by the resistance of the seawater acts in the direction opposite to the tension T. As shown in FIG. Therefore, it is assumed that the depth retention member 10 is subjected to a backward tilting force, that is, an overturning moment that causes the depth retention member 10 to rotate backward about the attachment point to the active cable 62 . Therefore, a weight may be provided at one end 31m of the front adjusting member 31 or at the end of the rod-shaped portion 31a on the one end 31m side to apply a force that cancels the overturning moment.

Next, referring to FIG. 4, the focus unit 50 of FIGS. 1 and 2 and its peripheral configuration will be specifically described. A focus device 52 is attached to one end of the support member 51 via a fixing member 53 . The seismic source device 52 includes a non-explosive seismic source 52s that is friendly to the marine environment, and has a function of generating continuous waves. The seismic source 52s includes a piezoelectric element (piezo element), a giant magnetostrictive element, an underwater speaker, an electromagnetic vibrator, a hydraulic vibrator, or the like. In particular, the piezoelectric element type seismic source device 52 can be made smaller and lighter than an explosive seismic source such as an air gun. The epicenter 52s may output a wave (non-pulse wave) in which at least one of frequency, phase, and amplitude changes continuously or randomly. Each source 52s of each source unit 50 is configured to output sound waves having different waveforms. Each hypocenter 52s may be set to oscillate sound waves simultaneously, or may be set to oscillate sound waves with a predetermined time lag.

The submarine geological survey system 100 has a connecting member 55 that is provided at a central position in the longitudinal direction of the shipboard and connects the supporting member 51 to the position. That is, the support member 51 is attached to the board by the connecting member 55 . The support member 51 is arranged to extend in the vertical direction. The structure and shape of the connecting member 55 are not limited to the example shown in FIG. 4, and various structures and shapes can be adopted. The connecting member 55 may be configured as a clamp, for example. Further, the submarine geological exploration system 100 may be configured to have a plurality of connecting members 55 . In this case, for example, a plurality of connecting members 55 may be provided along the vertical direction. In this way, the focus unit 50 can be fixed more firmly to the shipboard.

Here, although the ship 500 is relatively slow during exploration, the ship 500 is advanced at a relatively high speed when moving, such as when heading to an exploration point. Therefore, in order not to put a burden on the epicenter device 52, it is necessary to raise the epicenter device 52 to the sea when moving. In this respect, the submarine geological exploration system 100 comprises the seismic source unit 50 with the support member 51 and the seismic source device 52, and the support member 51 is fixed to the side by the connecting member 55. Installation and removal from the ship become easier, and work efficiency can be improved.

The connecting member 55 may have a configuration in which the supporting member 51 is rotatably connected about the connecting portion of the supporting member 51 . That is, the connection member 55 may have a rotation mechanism that rotates the epicenter unit 50 around the connection point. More specifically, the connecting member 55 enables the epicenter unit 50 to rotate in the direction of the white arrow on the stern side in FIG. 4, the direction of the white arrow on the bow side in FIG. 4, or both directions. You may adopt the structure which connects. In this case, the connecting member 55 may have a locking mechanism for stopping the pivoting of the epicenter unit 50 by the pivoting mechanism, and another member may be used to stop the pivoting of the epicenter unit 50 by the pivoting mechanism. Unit 50 may be fixed to the side of ship 500 .

For example, when the submarine geological exploration system 100 has two connecting members 55, one connecting member 55 is configured to have a rotating mechanism similar to a universal clamp, and the other connecting member 55 is configured as shown in FIG. A device having only such a fixing function may be used. In this way, if a rotation mechanism is adopted for the connecting member 55, the support member 51 can be kept in a state perpendicular to the sea surface during towing, so that the seismic source device 52 can be submerged in the sea, and the support member 51 can be rotated during movement. By moving it to a state parallel to the sea surface, the epicenter device 52 can be easily lifted from the sea. That is, by adopting such a configuration, workability can be further improved, and the efficiency of three-dimensional geophysical exploration can be enhanced.

The submarine geological exploration system 100 has an exploration control device 70 that performs analysis processing on reflected waves received by the plurality of geophones 62a. A functional configuration example of the exploration control device 70 of FIG. 1 will be described with reference to FIG. As shown in FIG. 5 , the exploration control device 70 has a communication section 71 , a control section 72 , a storage section 73 , an input section 74 and a display section 75 . The communication unit 71 is an interface for the control unit 72 to perform wired or wireless communication with external devices such as the plurality of geophones 62a. The storage unit 73 stores various information in addition to the operation program of the control unit 72 . The storage unit 73 is composed of RAM (Random Access Memory), ROM (Read Only Memory), flash memory, SSD (Solid State Drive), HDD (Hard Disk Drive), or the like. The input unit 74 includes, for example, a keyboard and a pointing device such as a mouse or trackball. The input unit 74 receives an input operation by the user and outputs an operation signal to the control unit 72 according to the content of the received operation. The display unit 75 is composed of, for example, a liquid crystal display (LCD), and displays various information according to instructions from the control unit 72 .

The control unit 72 executes processing related to three-dimensional geophysical exploration. The control unit 72 has input processing means 72a, output processing means 72b, oscillation processing means 72c, and analysis processing means 72d. The input processing means 72a executes processing according to operation signals obtained from the input unit 74 . For example, the input processing means 72a outputs a control signal indicating the content of the operation to at least one of the output processing means 72b, the oscillation processing means 72c, and the analysis processing means 72d in response to the user's input operation. The output processing means 72b causes the display section 75 to display various information according to the control signal from the input processing means 72a. For example, the output processing unit 72b adds information to the display screen of the display unit 75, changes information on the display screen, and transitions the display screen. The user can perform data input and setting processing through the input unit 74 while viewing the display screen of the display unit 75 . The output processing means 72b may have a function of displaying the three-dimensional data generated by the analysis processing means 72d on the display section 75. FIG.

The oscillation processing means 72c has a function of alternately oscillating sound waves from the hypocenters 52s of the two epicenter devices 52 at regular intervals. The oscillation processing means 72c oscillates a continuous wave from the epicenter 52s of the epicenter device 52 and stops the oscillation in response to an operation by the user or at set timing. The oscillation processing means 72c may oscillate sound waves of different waveforms from the respective epicenters 52s of the respective epicenter devices 52, or may oscillate sound waves of the same waveform. The oscillation processing means 72c may simultaneously oscillate sound waves from each epicenter 52s, but in this case, it is preferable to oscillate sound waves having different waveforms from each epicenter 52s.

The analysis processing means 72d extracts reflected waves corresponding to the focus device 52 from the received waves of the plurality of geophones 62a. The received wave of the geophone 62a is output from the seismic source 52s of the seismic source device 52, and in addition to the sound wave component reflected by the sea floor or the stratum boundary surface, etc., the sound wave component emitted from the propulsion device of the ship 500, waves, and streamer cables. 60 is a composite wave including ambient environment components such as noise components during towing. The submarine geological exploration system 100 of Embodiment 1 oscillates a chirp wave from the epicenter 52s of the seismic source device 52, and the analysis processing means 72d performs cross-correlation processing of the received wave and the chirp wave from the received composite wave. Extract the reflected wave component.

More specifically, when the analysis processing means 72d acquires the waveform signal of the composite wave received by the geophone 62a in the streamer cable 60, it calculates the cross-correlation between the waveform signal and the oscillation wave output from the seismic source device 52. A reflected wave of the oscillation wave is extracted by cross-correlation processing. In the first embodiment, the streamer cable 60 provided on the ship 500 receives the reflected wave corresponding to the oscillation wave from the focus device 52 provided on the starboard side or the port side of the streamer cable 60 on both the left and right sides. extracted from the composite wave of the device 62a. Based on the extracted reflected waves, the analysis processing means 72d generates three-dimensional data relating to seafloor geology. The control unit 72 can be configured by an arithmetic device such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and a program that cooperates with the arithmetic device to realize the various functions described above. The search control device 70 is configured by a desktop PC (Personal Computer), a notebook PC, or the like.

As described above, the seismic source unit 50 includes a rod-shaped support member 51 attached to a central portion in the longitudinal direction of the board, and a seismic source device including a seismic source 52s attached to one end of the support member 51 and oscillating sound waves. 52 and . Therefore, in the focus unit 50, the position of the focus device 52 connected to the support member 51 is stabilized by attaching the support member 51 to the side. In other words, since the focus unit 50 is configured so that the position of the focus device 52 with respect to the ship 500 can be fixed, there is no need for arithmetic processing that considers the position change of the focus 52s, and the effect of air bubbles due to the propeller wake etc. is eliminated. can be reduced. Therefore, it is possible to simplify the arithmetic processing at the time of analysis and improve the search accuracy. In addition, since the vertical position of the seismic source device 52 can be changed by adjusting the mounting position of the support member 51, the water depth position of the seismic source device 52 can be flexibly adjusted according to the water depth of the sea area to be explored. can be done. In addition, since the focus unit 50 can be easily attached and detached regardless of the type and size of the ship 500, convenience can be improved. Further, since the focus unit 50 can be easily removed from the shipboard, work such as cleaning and maintenance of the focus device 52 can be performed easily and inexpensively.

The submarine geological exploration system 100 has an epicenter unit 50, and a connection member 55 provided at a central location in the longitudinal direction of the shipboard and connecting a support member 51 to the location. By using the connecting member 55 when fixing the supporting member 51 to the shipboard, it becomes easy to attach and detach the seismic source unit 50 to and from the shipboard, so that work efficiency can be improved. In other words, by using the connecting member 55 provided on the shipboard, the support member 51 can be easily attached to the shipboard and easily removed from the shipboard, thereby improving work efficiency. In addition, since the vertical position of the epicenter 52s of the epicenter unit 50 can be changed by adjusting the connection point of the support member 51 with the connection member 55, the target depth of the active cable 62 and the depth of the sea area to be explored can be adjusted. Accordingly, the water depth position of the epicenter 52s can be flexibly adjusted.

The connection member 55 may be configured to connect the support member 51 so as to be rotatable around the connection point of the support member 51 . By adopting such a configuration, work such as sinking the epicenter device 52 in the sea during towing and raising the epicenter device 52 from the sea during movement can be performed more quickly, so that work efficiency can be improved.

When two streamer cables 60 are towed by a ship 500 as shown in FIG. A retaining member 10 may be attached. That is, the submarine geological exploration system 100 may have two epicenter units 50 . A pair of hypocenters 52s are arranged at a laterally widened position in the center of the ship 500 in the longitudinal direction, and a pair of streamer cables 60 in which the depth of the active cable 62 is adjusted and held are spaced apart from the left and right of the stern. By being thrown into the sea with a gap between them, it is possible to increase the measurement width at one time according to the principle of exploration.

The depth retention member 10 of Embodiment 1 has a depth adjustment section 30 that is connected to the fixed member 22 at an intermediate position between the two floating bodies 21 and one end of which is connected to the active cable 62 . The length of the depth adjusting portion 30 from the joint with the fixing member 22 to one end is set based on the target depth of the active cable 62 . More specifically, the depth adjustment unit 30 has two rod-shaped adjustment members 31 that are connected to the fixed member 22 at the other end 32b and extend from the other end 32b to the one end 32a. The two adjustment members 31 are connected to the fixed member 22 along the axial direction of the active cable 62 with a predetermined distance therebetween. With such a configuration, the length of the depth adjusting section 30 can be directly connected to the depth of the active cable 62, so the depth of the active cable 62 can be adjusted to and maintained at the target depth. Also, by changing the length of the adjusting member 31, the depth of the active cable 62 can be flexibly adjusted.

That is, in the conventional configuration, in order to adjust the depth of the streamer cable 60 , it is necessary to attach a plurality of control devices (such as birds) having a depth control function to the streamer cable 60 . Such a control device has a complicated configuration, involves complicated processing, and is costly. Therefore, it is desired to adjust and hold the depth of the active cable 62 with a member having a simple structure. In this regard, since the depth holding member 10 of Embodiment 1 has the above configuration, it is possible to adjust and hold the depth of the active cable 62, thereby reducing the user's work load. You can keep costs down.

The submarine geological exploration system 100 according to Embodiment 1 includes an epicenter unit 50 provided on at least one of the left and right sides of a ship 500, and two depth retention members 10 having any one of the configurations described above. ,have. Two depth retention members 10 are provided at both ends of the active cable 62 . Therefore, since the depth of the active cable 62 can be adjusted and held at both the front end and the rear end, the overall depth of the active cable 62 can be brought closer to the target depth more reliably.

Since the submarine geological exploration system 100 can also be used for shallow water (the water depth of the exploration sea area is shallower than about 100 m), it is also assumed that a relatively short streamer cable 60 is towed in a narrow sea area. Therefore, the depth retention member 10 and the focus unit 50 are required to have a simple overall configuration from the viewpoint of workability, operation cost, and the like. In this regard, since the depth retention member 10 and the focus unit 50 of Embodiment 1 have the simple configurations as described above, it is possible to improve workability and reduce operating costs.

<Modification>
A depth holding unit 150 according to a modification of the first embodiment will be described with reference to FIG. The depth of field retention unit 150 includes the depth of field retention member 10 described above, and a rotating member 90 provided on the active cable 62 to allow the adjusting member 31 to rotate with respect to the active cable 62 .

A rotating member 90 illustrated in FIG. 6 has a rotating mechanism portion 91 and a pedestal portion 92 . The rotation mechanism part 91 is configured by, for example, a split type bearing. The rotation mechanism 91 is an outer ring rotatable around the inner ring 5a by a plurality of rollers or balls (not shown) provided between the inner ring 5a fixed to the active cable 62 and the inner ring 5a. and a portion 5b. The pedestal portion 92 is fixed to the outer ring portion 5b or formed integrally with the outer ring portion 5b.

One end portion 32 a of the adjusting member 31 is fixed to the rotating member 90 by a fixture 45 . The pedestal portion 92 illustrated in FIG. 6 is provided with holes corresponding to the U-shaped attachments 45 at both ends in the front-rear direction. Each end of the fixture 45 passing through the ring of the one end 31m is inserted into each hole of the pedestal 92 and fastened with a fastener such as a nut, thereby fixing the adjusting member 31 to the rotating member 90. be. Since the rotation mechanism 91 has a split structure, it can be easily attached to an arbitrary position of the active cable 62 . The structures of the rotating member 90 and the fixture 45 are not limited to the example shown in FIG.

Before and after the streamer cable 60 is mounted on the ship 500, the twisting of the streamer cable 60 is removed. However, it is difficult to completely eliminate twisting, and it is even more so when the streamer cable 60 is elongated. Then, if the streamer cable 60 with the remaining twist is put into the sea, the distribution of the twist changes during towing, and it is conceivable that the twist will be concentrated at a specific point. Therefore, it is assumed that the depth retention member 10 is tilted in a direction caused by the twisting torque of the streamer cable 60 . In this regard, since the depth retention unit 150 in the modified example has the rotation member 90 , it can be attached to the active cable 62 so as to be rotatable. Therefore, even if the streamer cable 60 remains twisted, the force applied to the adjustment member 31 due to the twist can be released by the action of the rotating member 90 . Therefore, since the orientation of the adjusting member 31 can be maintained in a state perpendicular to the fixing member 22, the depth of the active cable 62 can be more stably maintained.

Embodiment 2.
A configuration example of the depth retention member 110 according to the second embodiment of the present invention will be described with reference to FIG. The overall configuration of the submarine geological exploration system 100 is the same as the example of the first embodiment based on FIGS. 1 and 2. FIG. The configuration of the focus unit 50 is the same as the example of the first embodiment based on FIG. The configuration of the exploration control device 70 is the same as the example of the first embodiment based on FIG. The same reference numerals are given to the same constituent members as in the first embodiment described above, and redundant explanations are omitted. Definitions of the x-axis direction, the y-axis direction, and the z-axis direction are the same as in FIG.

The depth retention member 110 includes two floating bodies 21 having the same shape, a fixed member 22 to which the two floating bodies 21 are fixed with a gap, and a fixed member 22 connected to an intermediate position between the two floating bodies 21, and a depth adjuster 130 having one end connected to the active cable 62 . The depth adjustment part 130 has a length from the joint with the fixing member 22 to one end, which is set based on the target depth of the active cable 62 .

As shown in FIG. 7, the fixing member 22 has a pair of outer members 22a that are formed in a rod-like or plate-like shape and connect the two floating bodies 21 together. The pair of outer members 22a are arranged in parallel with a predetermined distance therebetween. The fixed member 22 of FIG. 7 has an inner member 22b arranged parallel to and between a pair of outer members 22a. In addition to the shape, number, and arrangement of each assembly member in the fixing member 22, the method of fixing the two floating bodies 21 is not limited to the example of FIG. 7, and various variations can be selected.

The depth adjustment section 130 has a frame section 35 in which rod-shaped members are connected in a rectangular shape. The frame portion 35 is connected to the fixed member 22 by a connecting tool 48 . The frame portion 35 is arranged such that the direction from the joint with the fixing member 22 to the one end portion 35m, which is the end portion arranged downward, is the longitudinal direction of the rectangular shape. The frame portion 35 has two long rod members 35a along the longitudinal direction and two short rod members 35b along the width direction. The frame portion 35 is connected to the pair of outer members 22a such that the length from the connecting point to the one end 35m, that is, the length from the connecting point to the short rod member 35b arranged below can be adjusted. It is One short rod member 31 b corresponding to one end 35 m is connected to the active cable 62 so that the short side direction of the rectangular shape is parallel to the axial direction of the active cable 62 .

The depth adjustment section 130 of FIG. 7 has a support member 36 that connects a pair of long rod members 35a. Although FIG. 7 illustrates the depth adjustment unit 130 having three support members 36, the present invention is not limited to this, and the number of support members 36 can be changed as appropriate. The depth adjustment part 130 of FIG. 7 includes a connection point between one long rod member 35a and a short rod member 35b and a connection point between the other long rod member 35a and a short rod member 35b adjacent to the short rod member 35b. It has a reinforcing member 37 that connects the Although FIG. 7 shows an example having two reinforcing members 37, the present invention is not limited to this, and the number of reinforcing members 37 can be changed as appropriate. The frame portion 35, the support member 36, and the reinforcing member 37 may be made of an aluminum pipe, a PVC pipe, or the like. It's good to make it a thing.

The depth retention member 110 may have a weight (not shown) provided at one end 35 m of the frame 35 . More specifically, the weight is preferably provided at least one of the lower ends of the short rod member 35b and the long rod members 35a arranged below. As the weight, a weight containing lead, such as a lead sheet or a rod-shaped lead block, can be preferably used as described above. When weights are provided on both the lower ends of the two long rod members 35a, the weights of the same weight are provided on the lower ends of the respective long rod members 35a to achieve a good front-rear balance. However, by providing a weight only at the lower end of the front long rod member 35a or by increasing the weight of the weight at the lower end of the front long rod member 35a, even if a force that cancels the overturning moment is applied. good. When a weight is provided on the short rod member 35b arranged below, balance adjustment in the front-rear direction may be performed by adjusting the position in the front-rear direction.

Other configurations and alternative configurations are the same as those of the first embodiment described above. The configuration of the modification of the first embodiment can also be applied to the configuration of the second embodiment. In other words, the depth of field holding member 110 and the rotating member 90 provided on the active cable 62 and allowing the frame portion 35 to rotate with respect to the active cable 62 may constitute the depth of field holding unit. In this case, one end portion 35m of the frame portion 35, that is, the short rod member 35b arranged below, is fixed to the rotating member 90 by the fixture 45. As shown in FIG.

As described above, in the depth retention member 110 of the second embodiment, the pair of outer members 22a connecting the two floating bodies 21 are arranged in parallel with a predetermined distance therebetween. The frame portion 35 is arranged so that the direction from the connecting portion with the fixing member 22 to the one end portion 32a is the longitudinal direction of the rectangular shape, and is connected to the pair of outer members 22a. The length of the frame portion 35 from the joint with the outer member 22 a to the one end portion 35 m is set based on the target depth of the active cable 62 . Therefore, the depth of the active cable 62 in the streamer cable 60 can be adjusted and maintained.

In addition, the frame portion 35 has two long rod members 35a along the longitudinal direction and two short rod members 35b along the width direction. is connected to the active cable 62 so that the lateral direction of the rectangular shape is parallel to the axial direction of the active cable 62 . Therefore, the active cable 62 can be stably fixed along the short rod member 35b. Note that the number of connectors 42 that connect the short rod member 35b and the active cable 62 is not limited to the example shown in FIG. 7, and can be changed as appropriate. As the connecting device 42, various well-known connecting devices such as a fastening band can be adopted. The connector 42 may fix the active cable 62 over the entire area of the short rod member 35b, and may also function as a weight. The depth retention member 110 may have a weight provided at one end 35m of the depth adjustment section 130 . In this way, the depth retention stability of the active cable 62 can be enhanced.

The depth retention member 110 may be configured such that the mounting position of the frame portion 35 with respect to the fixed member 22 is variable. In other words, the frame portion 35 may have a variable connection point to the fixing member 22 . More specifically, the depth retention member 110 may be configured such that the length from the joint between the frame portion 35 and the pair of outer members 22a to the one end portion 35m of the frame portion 35 is adjustable. Here, since the depth retention member 110 is configured such that the distance from the connection point to the one end 35m is directly connected to the depth of the active cable 62, by making the attachment position of the frame 35 variable, Depth adjustment of the active cable 62 can be performed more flexibly.

Furthermore, according to the depth holding unit configured by the depth holding member 110 and the rotating member 90, even if the twist remains in the streamer cable 60, the force applied to the depth adjustment part 130 due to the twist is It can escape by the action of the rotating member 90 . Therefore, since the orientation of the depth adjusting portion 130 can be maintained in a state perpendicular to the fixing member 22, the depth of the active cable 62 can be more stably maintained. Other effects and the like are the same as those of the first embodiment described above.

Here, each embodiment described above is a specific example of the depth retention member, the depth retention unit, and the seafloor geological exploration system, and the technical scope of the present invention is not limited to these aspects. For example, each floating body 21 is not limited to a shape extending in one direction, and can take various shapes. That is, each floating body 21 may be circular in plan view, and may have approximately the same front and rear length and left and right length. Each floating body 21 preferably has a streamlined shape such as a circular shape or an elliptical shape in plan view at least at the front portion in the traveling direction, and the shape of the rear side is not limited.

In each of the above-described embodiments, an example in which the exploration control device 70 is installed on the ship 500 is shown, but the present invention is not limited to this. The exploration control device 70 may be provided in a facility on land or the like. In this case, the plurality of geophones 62a and the exploration control device 70 may communicate wirelessly via a repeater or the like. The exploration control device 70 may be configured by a cloud server based on cloud computing, an on-premise physical server, or a system combining these. The analysis processing means 72d may have only the extraction function of extracting the reflected wave from the composite wave. In this case, it is preferable to generate the three-dimensional data relating to the seafloor geology by using a data generation device provided in a facility on land or the like. The data generation device may be composed of a desktop PC, a notebook PC, a mobile terminal such as a tablet terminal, or the like. Note that the streamer cable 60 may be implemented with a microcomputer or the like for executing the extraction function of the exploration control device 70, or may be a digital streamer with a built-in A/D converter.

5a inner ring portion, 5b outer ring portion, 10, 110 depth retention member, 20 floating body portion, 21 floating body, 22 fixing member, 22a outer member, 22b inner member, 30, 130 depth adjusting portion, 31 adjusting member, 31a rod portion, 31b Short rod member, 31m one end, 31n other end, 32a one end, 32b other end, 35 frame, 35a long rod member, 35b short rod member, 35m one end, 36 supporting member, 37 reinforcing member, 41 connection tool, 42 connector, 45 fixture, 48 connector, 50 focus unit, 51 support member, 52 focus device, 52s focus, 53 fixing member, 55 connection member, 60 streamer cable, 61 lead-in cable, 62 active cable, 62a geophone, 62z termination, 64a rope, 64b rope, 66 GNSS antenna, 70 exploration control device, 71 communication unit, 72 control unit, 72a input processing means, 72b output processing means, 72c oscillation processing means, 72d analysis processing means, 73 storage unit, 74 input unit, 75 display unit, 90 rotation member, 91 rotation mechanism unit, 92 pedestal unit, 100 seafloor geological survey system, 150 depth retention unit, 500 ship.

A submarine geological exploration system according to an aspect of the present invention includes a plurality of geophones, a streamer cable towed by a ship , and a non-explosive type that oscillates sound waves for acquiring reflected waves by each geophone of the streamer cable. and a seismic source unit having a seismic source, wherein the seismic source unit includes a rod-shaped support member attached to a central location in the longitudinal direction of the board of the ship, and a seismic source, and is attached to one end of the support member. and a seismic source device.

A seafloor geological exploration system according to one aspect of the present invention includes a connection member that is provided at a central location in the longitudinal direction of the board along with the streamer cable and the seismic source unit described above, and that connects the support member to the location. be.

Claims (3)

A seismic source unit comprising a seismic source that oscillates sound waves for acquiring reflected waves on a plurality of geophones of a streamer cable towed by a ship,
A rod-shaped support member attached to a central location in the longitudinal direction of the ship's board;
a seismic source device including the seismic source and attached to one end of the support member. A source unit according to claim 1;
A seafloor geological exploration system, comprising: a connection member provided at a central location in the longitudinal direction of the board and connecting the support member to the location. The connecting member is
3. The seafloor geological exploration system according to claim 2, wherein said support members are connected so as to be rotatable about a connection point of said support members.

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