JP2005114485A - Traction-type multi-channel surface wave survey system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily survey surface wave with high precision by making less likely to be affected by stones on ground, cross wind, etc. and setting in optimum conditions, according to the investigation purpose and ground conditions. <P>SOLUTION: Two ropes 10 are extended in parallel, large number of oscillation receiver units 16 loading oscillation receivers 14 on a base member 12 are prepared and aligned with a specific intervals, and each oscillation receiver unit is spanned between the two ropes, to make whole set capable of traction in a series state. The oscillation units are provided with a mechanical binding mechanism 18 and can be attached to the rope at arbitrary positions with it, and thus the intervals of the receivers 14 can be freely controlled. The base member is almost rectangular plate in shape, and the front and back edges of the bottom are sloping surface or is a bent surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a towed multi-channel surface wave exploration device in which a large number of geophone units are fixed to two tow ropes or wires at an interval so that the whole can be pulled in a series of states. . More specifically, in the present invention, a large number of geophone units each having a geophone mounted on a base member can be installed at any position between two ropes or wires extended in parallel. This is a tow-type multichannel surface wave exploration device that makes it possible to receive surface waves with high accuracy at a large number of measurement points by making them optimally suited to the purpose of the survey and ground conditions. It is.

  One of the geophysical exploration methods using elastic waves is the surface wave exploration method. A surface wave is a wave that propagates near the ground surface among elastic waves, and has a property different from a body wave called a P wave or S wave. However, since the propagation velocity of surface waves is about 90 to 95% of the S wave velocity and has a propagation velocity close to that of the S waves, attempts have been made to obtain the S wave velocity distribution of the ground by observing the surface waves. Yes. This is because the S-wave velocity depends on the rigidity factor which is an engineering standard such as the hardness of the material, and provides a useful design index when designing a structure or the like on the ground.

  A wide-area survey is required for geological surveys in the civil engineering / architecture field, especially for safety checks such as river embankments and landfill / filled land compaction evaluations. Therefore, when applying surface wave exploration as a simple method for estimating the S-wave velocity structure of the ground, it is important that the measurement and analysis can be performed in a short time and the survey results can be obtained at low cost. .

  By the way, in the shallow seismic reflection seismic survey, a system has been developed in which a seismometer (vibrator) is fixed on a pulling belt, and the entire system can be pulled and easily measured (see Patent Document 1). Here, the traction belt is sandwiched between the pedestal on the ground side and the upper installation panel, the installation panel is fixed by tightening the installation panel to the pedestal with a plurality of bolts through the traction belt, and the seismometer is fixed to the installation panel Is disclosed. As a result, the seismometer can be installed on the ground in a non-fixed manner, and the measurement efficiency can be improved by pulling and changing the position.

  However, even though the conventional pulling type elastic wave exploration device described in Patent Document 1 is effective for the shallow reflection seismic exploration method, it is not necessarily suitable for the surface wave exploration method. Absent. Reflection method exploration receives vibrations in the frequency range of about 40 to 100 Hz, whereas surface wave exploration must receive vibrations in a lower frequency region (about 2 to 40 Hz). This is because it is easily affected by a decrease in coupling due to gravel existing in the water and a slight movement due to a cross wind, which may increase noise and reduce measurement accuracy.

Further, in the traction system using a belt, even if the seismometer can be attached to and detached from the installation panel, the pedestal remains fixed to the belt, and the seismometer interval cannot be changed. However, in surface wave exploration, it is necessary to adjust the geophone (seismometer) interval according to the survey purpose and ground conditions. For example, it is preferable to shorten the interval on soft ground, and increase the interval on hard ground. Actually, it is necessary to perform trial vibrations at different locations of the geophones and to arrange the geophones at preferred intervals for measurement. There is. However, in the prior art, since the distance between the geophones cannot be changed, it is necessary to prepare a plurality of traction belts with different pedestal mounting intervals in advance, which increases the cost and stores, transports, and handles many belts with pedestals. Etc. becomes very cumbersome.
JP 2002-62361 A

  The problem to be solved by the present invention is less susceptible to the effects of gravel on the ground and crosswinds, etc., and it is easy to perform accurate surface wave exploration by setting optimum conditions according to the purpose of the survey and ground conditions. Is to be able to.

  The present invention is an elastic wave exploration device in which a large number of geophone units having geophones mounted on a base member are fixed to a long member for towing at intervals, and the whole can be towed in a series of states. The long member for traction is composed of two ropes or wires that are extended in parallel so as to be continuous over the entire apparatus, and the base member has inclined front surfaces or curved surfaces at the front and rear end edges thereof. The base member is constructed between two ropes or wires by a mechanical fastening mechanism that can be mounted at any position, so that the distance between the geophones can be freely adjusted. Is a towed multi-channel surface wave exploration device.

  For example, the base member has a substantially rectangular plate shape, and the mechanical fastening mechanism includes rope or wire guide grooves formed on both sides of the upper surface of the base member, and base clamps respectively located above the front and rear portions of the base member. A rope or wire is sandwiched between them, and the base clamp is fastened and fixed to the base member with screws. Alternatively, the base member has a base body having a substantially rectangular plate shape, and a front wall and a rear wall erected along the front and rear surfaces thereof, and a through hole through which a rope or a wire can be inserted into the front wall and the rear wall The mechanical fastening mechanism may be a system in which a rope or a wire inserted through a through hole in the front wall and the rear wall of the base member is gripped by a clip fitting in front of the front wall and behind the rear wall.

  In these, on the bottom surface of the base member, a sled (ridge) portion extending in the front-rear direction or a roller that rolls only in the front-rear direction can be provided for imparting straightness and stability. Moreover, the structure which makes the windproof hood which covers a geophone a detachable on the upper surface of a base member is preferable. By installing a windproof hood when the crosswind is relatively strong, the generation of vibration due to wind can be suppressed. It is preferable that the tow rope is subjected to eye processing at both ends and the main body portion is color-coded or marked at regular intervals. If the end is eye-processed, it can be easily connected to the observation vehicle by a hook. In addition, the geophone unit can be easily installed at a predetermined interval without separately measuring the interval by color coding or marking.

  A configuration in which a traction stabilization unit is incorporated between the geophone units is also effective. As with the base member, the traction stabilization unit has a slanted or curved surface at the bottom and front and rear edges of the bottom, and a sledge that extends in the front-rear direction to provide straightness and stability to the bottom, or only in the front-rear direction. A structure in which rollable rollers or wheels are arranged. The base member of the geophone unit may be used as it is. If the weight is insufficient, a heavy object may be mounted on the base member. Such a traction stabilization unit is installed between two ropes or wires at one or more positions between a large number of geophone units by a mechanical fastening mechanism that can be mounted at an arbitrary position.

  Furthermore, the present invention uses such a towed multi-channel surface wave exploration device, collects and analyzes traces having the same center position of two traces using multi-channel data from a large number of geophones (CMP (Common This is a surface wave exploration method for obtaining a two-dimensional S-wave velocity structure from a result of obtaining a phase velocity by analyzing (Mid Point).

  Unlike a wide belt, the towed multi-channel surface wave exploration device of the present invention is pulled by two ropes or wires, so that it is not beaten by a crosswind and is not easily affected by vibrations caused by wind. In addition, since the front and rear edges of the base member are inclined or curved, large gravel on the ground is eliminated and small gravel can move over and is not easily affected by gravel. Proper coupling with the vessel is obtained. As a result, noise in a low frequency region can be reduced, and vibration receiving sensitivity is improved. Furthermore, the base member is installed on the rope or wire by a mechanical fastening mechanism that can be mounted at an arbitrary position, so that the distance between the geophones can be freely adjusted. They can be assembled freely, so that equipment costs can be reduced, storage and transportation can be facilitated, and high-precision data can be obtained because it can be carried out in a state suitable for the purpose of investigation and ground conditions.

  A geophone unit is configured by using a base member whose front and rear end edges are inclined surfaces or curved surfaces and fixing the geophone on the base member. The base member is installed between two ropes or wires arranged in parallel. This erection is performed by a mechanical fastening mechanism and can be mounted at an arbitrary position so that each geophone is arranged at a predetermined interval. It is preferable to make the windproof hood detachable with respect to the upper surface of the base member so that the geophone can be covered.

  FIG. 1 shows the overall configuration of an embodiment of a towed multi-channel surface wave survey apparatus according to the present invention. Here, A represents a plane and B represents a side surface. The towed multi-channel surface wave exploration device extends two ropes 10 in parallel so as to be continuous over the entire length of the device, and prepares a large number of geophone units 16 each equipped with a geophone 14 on a base member 12. A large number of geophone units 16 are arranged in a row at predetermined intervals, and each geophone unit 16 is installed between two ropes 10 so that the whole can be pulled in a series of states. . The geophone unit 16 includes a mechanical fastening mechanism 18 so that the geophone unit 16 can be attached to the rope 10 at an arbitrary position, so that the interval between the geophones 14 can be freely adjusted. Since it is attached to an arbitrary position of such a long continuous rope, any arrangement interval can be accommodated with only two ropes. The base member 12 has a substantially rectangular plate shape, and has a shape in which front and rear end edges of the bottom surface are inclined surfaces or curved surfaces.

  Ten to several dozen (for example, 24 to 48) geophone units 16 are attached to the rope 10 at intervals of about 50 cm to 2 m and pulled by the observation vehicle 20. The mounted geophone 14 receives an elastic wave having a low frequency of about 2 to 40 Hz. Among the elastic waves generated by the artificial vibration source 22 located on the array line of the geophone unit 16, the surface wave propagating in the vicinity of the ground surface is detected by each geophone 14, and the vibration signal is transmitted to the observation vehicle by the signal line 24. 20 data recording devices 26.

  The rope 10, the geophone unit 16, the signal line 24, and the like are each composed of independent units, and each unit is usually assembled before use. The mechanical fastening may be performed between the geophone unit 16 and the rope 10, and the mechanical fastening mechanism may be a simple structure such as a rope clamp, but a structure that can be easily attached and detached and can be firmly fixed is preferable. Thereby, the interval of the geophone unit 16 can be easily changed.

  The material of the rope is arbitrary, but in addition to having sufficient mechanical strength, use a rope that has low wear, excellent weather resistance, and low elongation to pull the ground surface. For example, a synthetic resin (polyester, polyethylene, aramid, etc.) rope is desirable. In addition, since the geophone unit is attached at an arbitrary position, the shape is the same over almost the entire length of the rope except for the end. Steel wires and the like can be used, but are often difficult to handle in terms of flexibility and weight, and therefore a resin rope is preferred. If it is a rope, it can be easily repaired by performing a knitting process such as weaving.

  The electrical fastening may be performed between the geophone unit and the signal line, and there is almost no need to consider the tensile strength. Therefore, the structure of the signal line itself and its connection structure are simplified. The change of the signal line take-out position accompanying the change of the distance between the geophone units can be bundled with a band or a string because the signal line is reduced in weight with a simple structure and can be easily changed. Depending on the length to be changed, the volume of the bundled signal lines becomes large. Therefore, it is desirable to securely fix the signal lines to the rope that is responsible for mechanical fastening.

  This towed multi-channel surface wave exploration device is usually assembled at appropriate intervals in the field according to the purpose of the survey or the ground conditions. It has been found that, even at the same exploration depth, in general, when the ground is soft, if the distance between the geophones is narrow, and when the ground is hard, if the distance between the geophones is wide, good surface wave vibration can be received. However, there are many uncertain factors. Therefore, trial vibration is received at different locations (for example, 50 cm, 1 m, and 2 m), and the optimum receiver interval is determined, assembled, and measured. In the present invention, it is possible to easily change such a geophone unit mounting position.

  The surface wave exploration detects vibrations in a low frequency region such as 2 to 40 Hz, and thus is generally easily affected by crosswinds. However, in the present invention, since it is towed by two ropes, there is no fear of being beaten even if it receives a cross wind, and it is difficult to be affected by fine movement caused by the wind.

  One embodiment of the geophone unit is shown in FIG. Here, A represents a state before fastening, B represents a state after fastening, in a perspective view, C represents a plane, and D represents a side surface. The base member 30 has a substantially rectangular plate shape, and an inclined surface 30a is formed on the front and rear end edges of the bottom surface. The geophone 32 is fixed by screwing a mounting screw 32 a on the lower surface thereof into a screw hole 30 b formed on the central upper surface of the base member 30. A base clamp 34 is used as a mechanical rope fastening mechanism. A shallow guide groove 30c for accommodating the rope is formed on both sides of the upper surface of the base member 30, and the rope 10 is clamped and fixed by the base clamps 34 arranged at the front and rear on the upper surface of the base member 30.

  The base clamp 34 has a curved rope holding portion 35a formed at both ends of the band plate 35, a knob-attached bolt 36 is inserted into the central hole 35b, and is screwed into a screw hole 30d provided in the base member 30 to be clamped. It is the structure which performs. Since this fastening mechanism only needs to tighten two bolts 36 with knobs, the assembling workability is very good. Of course, a structure that can be tightened with one touch may be adopted, but the screwing method is preferable in that the rope can be hardly displaced and the durability is excellent because the tightening can be adjusted. In order to make it difficult for the rope to slip with respect to the tension, although not shown in the drawing, one or more arc-shaped ridges are formed in the transverse direction in the rope guide groove of the base member, and the curved rope of the base clamp facing it If one or more arc-shaped protrusions are provided on the pressing portion, the resistance increases, which is effective in preventing deviation.

  The base member 30 is desired to be made of a material and a structure that can properly couple the ground and the geophone 32, are not overloaded during towing, do not become unstable towing, and are not easily worn or deformed. Therefore, it is made of a metal such as stainless steel or aluminum and has a shape in which inclined surfaces 30a and curved surfaces are formed on the front and rear end edges of the bottom surface. In this way, since there is a certain amount of weight, it stabilizes and does not finely move due to the influence of the wind, and even if there are gravel on the ground, it is eliminated if it is large, and it can be overcome if it is small. Although not shown in the figure, it may be formed in a boat shape in which the center of both front and rear ends is projected, and if so, the effect of removing gravel and the like increases.

  An example of the bottom shape of the base member is shown in FIG. A is the simplest example, and the bottom surface is a flat surface. B has a structure in which sled portions 40 having an inverted triangular cross section are attached to both sides over almost the entire length. It may be a structure that fits into the groove, or may be removable. In general, when viewed in cross section, the road surface has a convex shape such that the center is high in the width direction and both sides are slightly lowered due to drainage. Therefore, in surface exploration on the road surface, as the tow unit is connected to the rear side as it is pulled, it tends to curve so as to slip down to the road end. However, if the sled portions 40 are provided on both sides as in B, the resistance in the lateral direction is increased and the straightness is improved, so that it is easy to maintain the linear alignment state of each geophone unit. C is a structure in which short sled portions 41 are provided at two locations on the front (or rear) center and two sides on the rear (or front) (total of three locations). If it does in this way, since it will become a three-point support system, stability will improve. D is a structure in which rollers 42 that can roll only in the front-rear direction are arranged, and E is a structure in which wheels 43 are provided. In either case, the linear arrangement of each geophone unit during towing is improved. In E, instead of four wheels, a three-wheel structure may be used.

  Similar to the above base member, the front and rear edges of the bottom surface are inclined surfaces or curved surfaces, and the bottom surface is a sled portion extending in the front-rear direction for imparting straightness and stability, or can be rolled only in the front-rear direction. A structure in which rollers or wheels are arranged is effective in improving the traction stability. Therefore, it is also effective to incorporate the traction stabilization unit having such a structure between the geophone units. The traction stabilization unit may use the base member of the geophone unit as shown in FIGS. If the weight is insufficient, a heavy object may be mounted on the base member. Such a traction stabilization unit is installed between two ropes or wires by a mechanical fastening mechanism that can be mounted at an arbitrary position at one or more arbitrary positions between a large number of geophone units.

  In the present invention, various configurations combining such a geophone unit and a traction stabilization unit are possible. Only the geophone unit may be connected, or a traction stabilization unit may be combined therewith. Even when only the geophone unit is connected, ones having different bottom structures may be combined. For example, there is a configuration in which the bottom geophone unit as shown in FIG. 3A is mainly used and the bottom geophone units as shown in FIGS. Alternatively, a configuration in which a bottom geophone unit as shown in FIG. 3A is a main body and one or more bottom traction stabilization units as shown in FIGS. In particular, the latter can detect ground vibrations efficiently with a simple bottom-shaped geophone unit, and the traction stabilization unit with a special bottom structure can be towed linearly and stably along the measurement line, facilitating work. There are advantages.

  FIG. 4 shows another example of the mechanical fastening mechanism. The base member 50 includes a base body 51 having a substantially rectangular plate shape, and wall portions (front wall and rear wall) 52 erected along the front and rear surfaces thereof, and the rope 10 can be inserted into the wall portion 52. The structure has a through hole, and a geophone 32 is mounted at the center of the upper surface. The mechanical fastening mechanism is a system in which the rope 10 that is inserted through the through hole of the wall portion 52 of the base member 50 is gripped by a clip fitting at the front of the front wall and the rear of the rear wall. The clip metal fittings are U-shaped bolts 54, which are provided outside the front wall and the rear wall so as to surround the rope 10, and both ends are inserted into the holding plate 55 and tightened with nuts 56.

  Another example of the structure for fixing the geophone 32 to the base member is shown in FIG. A is provided with a through hole 61 in the center of the base member 60 and a recess 62 on the bottom surface side so as to surround it, and through the through hole 61 a vibration receiving device mounting screw 63 is inserted and tightened with a mounting nut 64 from the bottom surface. This is a structure in which 60 is sandwiched and fixed. This structure has an advantage that a geophone having a different screw shape can be fixed to the base member. B is a structure that is fixed to the base member 68 using clay 66. If there is no suitable nut, or if the geophone mounting screw is extremely short, it can be fixed in this way.

  FIG. 6 shows an example in which the base member 30 is covered with a hood 68 to cover the geophone 32 and the like as a measure against cross wind. The towed multi-channel surface wave exploration device according to the present invention uses the rope 10 for towing, so that there is no particular problem with a slight crosswind. However, when a cross wind becomes prominent, it is preferable to install a hood 68 that covers the entire top surface of the base member 30. For example, it can be easily attached to and detached from the base member as a streamlined synthetic resin molded product. Surface wave exploration is often performed in areas that are subject to crosswinds, such as river dikes, and a configuration in which a hood can be attached and detached is effective. As a result, it is possible to reduce the influence of vibration caused by the cross wind as much as possible.

  FIG. 7 shows an example of the rope 10 used for towing. If the eye processing 10a is applied to both ends, it is possible to attach the observation vehicle with a hook, and the workability is improved. In addition, the eye processing is applied to both ends, and sometimes it is pulled not only in one direction but also in the reverse direction in order to finely adjust the position, and a large number of geophone units are reciprocated to align them linearly. This is because there are cases. Further, as shown in the figure, it is also effective to change the color alternately for every fixed length of the majority 10b excluding the eye-finished end of the rope. Marking may be applied. In the present invention, the mounting position of the geophone unit can be freely changed. Therefore, if the color is changed, for example, every 50 cm, the geophone unit can be easily installed at a predetermined position by using it as a guide.

  FIG. 8 shows a moving carriage for winding a wire to which a base member is attached. This is a structure in which a take-up drum 72 is mounted on a wheeled hand truck 70. The developed surface wave exploration device can be easily withdrawn by rotating the winding drum 72 and winding it. Further, it can be easily deployed simply by pulling out from the take-up drum 72. This is particularly effective when using a hard wire such as steel. Since the rope is excellent in flexibility, it can be folded and stored without using such a winding drum.

  FIG. 9 shows a line return tool for linearly aligning the geophone unit along the line. As mentioned above, the road surface is lower than the center because of drainage. When the row of the geophone units 80 is pulled, the rear geophone unit is displaced to the side and may be displaced from the measurement line. This is a structure in which a handle 84 is erected on a moving body 83 having two wheels 81 on the front and rear sides and a modification plate 82 curved sideways on the front and rear sides. When the operator holds the handle 84 and moves the moving body 83 along the survey line, the geophone unit deviating from the survey line can be returned along the survey line. In order to correct the position of the geophone unit, an operator does not have to bother crouching and moving the geophone unit, so workability is improved.

  Using such a towed multi-channel surface wave exploration device, using multi-channel data from a large number of geophones, collecting traces with the same center position of two traces and analyzing (CMP analysis) The two-dimensional surface wave velocity distribution is obtained, and the two-dimensional S wave velocity structure can be obtained from the result. Attach a shot mark generator that gives the recording device the timing when the artificial vibration source is excited, transmit the shot mark to the recording device at the moment of vibration, and start data recording.

The obtained data is analyzed by the following procedure, for example.
(1) Calculate cross-correlation for all possible combinations of two traces for every common origin point recording.
(2) Collect all cross-correlation where the center positions of the two traces are the same location from all the starting point records.
(3) Polymerize those with the same receiving point interval.
(4) Since cross-correlation with different receiving point intervals cannot be directly superposed, the records obtained by superimposing the cross-correlation with the same receiving point interval previously arranged are arranged according to the receiving point intervals. This is called pseudo common oscillation point recording.
(5) The pseudo common oscillation point recording is converted into a frequency domain for each trace, and then a phase shift according to the oscillation point interval is given to integrate the spatial method. By this procedure, the distance-time pseudo common oscillation point record can be converted into an apparent velocity distribution in the frequency domain.
(6) In the frequency-phase velocity plot, the phase velocity having the largest amplitude for each frequency is read and used as a phase velocity curve (dispersion curve).
(7) A one-dimensional S-wave velocity structure is obtained by inverse analysis from the dispersion curve by a non-linear least square method.
(8) In the two-dimensional S-wave velocity structure analysis, in a one-dimensional inverse analysis process, the analysis is performed while relating adjacent or neighboring dispersion curves and velocity structures.
Thereby, an S wave velocity structure with good continuity in the horizontal direction can be obtained.

  INDUSTRIAL APPLICABILITY The present invention can be used for surveying the degree of soundness of paved or unpaved roads, river dikes, etc., or surveying residential land created by landfill.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of one Example of the surface wave search apparatus which concerns on this invention. Explanatory drawing which shows one Example of a geophone unit. Explanatory drawing which shows the example of the bottom face shape of a base member. Explanatory drawing which shows the other example of a mechanical fastening mechanism. Explanatory drawing which shows the other example of the structure which fixes a geophone to a base member. Explanatory drawing which shows the example which put the hood on the geophone unit. Explanatory drawing which shows an example of a rope. Explanatory drawing of a moving trolley | bogie. Explanatory drawing of a survey line return tool.

Explanation of symbols

10 rope 12 base member 14 geophone 16 geophone unit 18 fastening mechanism 20 observation vehicle 22 artificial vibration source 24 signal line 26 data recording device

Claims (7)

An elastic wave exploration device in which a large number of geophone units having geophones mounted on a base member are fixed to a long member for towing at intervals, and the whole can be towed in a series of states. The long member is composed of two ropes or wires extending in parallel so as to be continuous over the entire device, and the base member has a shape in which the front and rear end edges of the bottom surface are inclined surfaces or curved surfaces. The base member is constructed between two ropes or wires by a mechanical fastening mechanism which can be mounted at an arbitrary position, whereby the distance between the geophones can be freely adjusted. Multi-channel surface wave probe. The base member has a substantially rectangular plate shape, and the mechanical fastening mechanism is between a rope or wire guide groove formed on both sides of the upper surface of the base member and a base clamp located above the front and rear portions of the base member. 2. The towed multi-channel surface wave survey device according to claim 1, wherein a rope or wire is sandwiched and a base clamp is fastened and fixed to a base member with a screw. 3. A towed multi-channel surface wave exploration device according to claim 1, wherein a sled portion extending in the front-rear direction for imparting straightness and stability, or a roller or a wheel capable of rolling only in the front-rear direction is arranged on the bottom surface of the base member. . A structure in which the front and rear end edges of the bottom surface are inclined surfaces or curved surfaces, and a sled portion extending in the front-rear direction for imparting straightness and stability to the bottom surface, or a roller or wheel that can roll only in the front-rear direction. The traction stabilization unit is constructed between two ropes or wires at one or more positions between a plurality of geophone units by a mechanical fastening mechanism that can be mounted at an arbitrary position. A towed multi-channel surface wave exploration device according to any one of the above. The tow type multi-channel surface wave exploration device according to any one of claims 1 to 4, wherein a windproof hood that covers the geophone is detachable on an upper surface of the base member. The tow-type multichannel surface wave survey device according to any one of claims 1 to 5, wherein the tow rope is subjected to eye processing at both ends, and the main body portion is color-coded or marked at regular intervals. Using the towed multi-channel surface wave survey device according to any one of claims 1 to 6, using multi-channel data from a large number of geophones, collecting and analyzing traces having the same center position of two traces The surface wave exploration method which calculates | requires a phase velocity by this and calculates | requires a 2-dimensional S wave velocity structure from the result.

Images