Ex. PGS 1005
`
`EX. PGS 1005
`
`
`
`
`
`

`
`United States Patent
`
`[II] 3,581,273
`
`[721
`
`[21 I Appl. No.
`[221 Filed
`[ 45 I Patented
`
`Inventor Ronald M. Hedberg
`18 Whittier St., Cambridge, Mass. 02140
`875,510
`Nov. 10, 1969
`May 25,1971
`Continuation of application Ser. No.
`645,643,June 13, 1967.
`
`[54] MARINE SEISMIC EXPLORATION
`13 Claims, 13 Drawing Figs.
`[52] U.S. CI........................................................ 340/7PC,
`114/237, 181/0.5VM, 340/15.5MC
`Int. Ct ..................................... , ................... G01v 1/38
`[51]
`[50] Field of Search ............................................ 340/7, 15.5
`MRC; 114/237; 181/.5 VM
`
`[56]
`
`Re25,204
`3,019,412
`
`References Cited
`UNITED STATES PATENTS
`7/1962 Becker ........................ .
`1/1962 Crawford .................... .
`
`340/15.5
`340/7
`
`6/1967 Ballard ........................ .
`3,325,778
`7/1967 Kilmeretal. ................ .
`3,331,050
`Primary Examiner-Richard A. Farley
`Assistant Examiner-Daniel C. Kaufman
`Attorney-Sperry and Zoda
`
`340/7
`340/7
`
`ABSTRACT: Continuous marine seismic explorations are car(cid:173)
`ried out by providing echo detecting means with control
`means for maintaining the echo detecting means in fixed or
`predetermined positions and at spaced points in two dimen(cid:173)
`sions of a horizontal plane, and by generating echo producing
`impulses at one or more spaced points located in fixed or
`predetermined relative positions with respect to each other
`and in said plane. In this way, a set of records may be obtained
`which define the seismic interfaces of the prospect under sur(cid:173)
`vey in two intersecting vertical planes. Thereafter, by produc(cid:173)
`ing successive sets of such records, quadratic surfaces in
`which the true inclinations of interfaces may be determined
`over an extended area are obtained in a single traverse
`thereof. At the same time, the accuracy of the records ob(cid:173)
`tained is materially increased.
`
`Ex. PGS 1005
`
`

`
`PATENTED NAY251971
`
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`3,581,273
`
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`
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`PATENTED MAY251971
`
`3.581. 273
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`PATENTED MAY251971
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`
`

`
`PATENTED NAY 2 51971
`
`3,581.273
`
`SHEET 5 OF 5
`
`RADAR-
`CONTROL
`
`98
`----------------
`
`RADAR
`RErLE"CTOR.
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`Ex. PGS 1005
`
`

`
`3,581,273
`
`1
`MARINE SEISMIC EXPLORATION
`
`RELATED APPLICATION
`
`This application is a continuation of copending application
`Ser. No. 645,643, filed June 13, 1967.
`Preferred equipme·nt used for obtaining such records in(cid:173)
`cludes steerable means such as paravanes for maintaining the
`impulse generating devices and echo responsive elements in
`known or predetermined relative positions when producing
`the successive sets of records. Furthermore, when inscribing
`such records, the individual records of each set may be
`brought into registry with each other so as to facilitate correla(cid:173)
`tion and interpretation of the records obtained.
`
`BACKGROUND OF THE INVENTION
`
`2
`mined points spaced apart in two directions to provide a"(cid:173)
`cross spread" within a horizontal plane. For this purpose the
`equipment used preferably also includes means for maintain(cid:173)
`ing the impulse generating and echo receiving means in such
`5 fixed or predetermined relative positions during survey as to
`assure the accuracy of the records produced, and may if
`desired embody means for controlling the record producing
`means so as to compensate for any dislocation or deviation of
`10 the impulse generating and echo producing means from such
`predetermined positions.
`Accordingly, it is possible to generate a set of echo produc(cid:173)
`ing impulses from which accurate records may be obtained by
`energizing one or more impulse sources located at the desired
`15 and predetermined points which may be spaced with respect
`to each other in two directions in a horizontal plane above the
`area under survey. When such sources are energized succes(cid:173)
`sively and in such a manner as to permit a separate record of
`the echo or reflected waves derived from each of the spaced
`20 impulse sources to be produced, or to permit resolution of the
`reflections from a single impulse source into two distinct
`nearly vertical planes containing the points of reflection, so
`that these planes arc oriented at a substantial angle to each
`25 other, or so that these planes are widely spaced, it is then
`possible to survey the area with greatly increased speed and
`accuracy. Thus, each record of the set of echoes obtained
`fronj multiple sources will indicate the profile of the area and
`strata under survey in a substantially vertical plane passing
`30 through the echo producing strata. Because the separation of
`the teflection points is sufficient to permit resolution of the
`positions of seismic horizons outside the plane of traverse of
`the ~urvey ship, the true inclination of reflecting strata may be
`dete"rmined. Repeated sets of such records obtained by re(cid:173)
`peated operations carried out in a single traverse of the area
`under survey will thus serve to indicate the structural configu(cid:173)
`ration of the entire area with greater accuracy than has been
`possible heretofore.
`The equipment employed in accordance with the present in-
`vention further serves to coordinate the individual records of
`each set of impulses whereby the nature of the structure in(cid:173)
`dicated by any set of impulses can be quickly and easily deter(cid:173)
`mined.
`
`35
`
`I. Field of Invention
`This invention relates to methods and means for use in
`marine seismic exploration and is directed particularly to
`systems and equipment whereby records may be obtained to
`indicate the profile of the area under survey as a series of sub(cid:173)
`stantially vertical orthogonal sections proceeding in
`the
`direction in which said area is traversed.
`2. Description of the Prior Art
`It has been common practice heretofore to carry out marine
`seismic surveys by employing a number of hydrophones that
`are connected by electrical conductors to recording equip(cid:173)
`ment, and are towed behind a boat moving over the area to be
`surveyed. The hydrophones are thereby stretched out in a
`straight line or "spread," after which an echo producing im(cid:173)
`pulse, such as an explosive blast, spark or the like, is generated
`at a point along or beside the spread of hydrophones. The
`resulting echoes from the surface and underlying strata are
`recorded to indicate the profile and/or character of the area
`being surveyed.
`Such systems serve to produce a record which indicates the
`profile of the strata in a single, substantially vertical plane
`beneath the "spread" and it is therefore necessary to traverse
`the area under survey repeatedly in order to obtain a complete
`record of the.area and a clear indication of the various slopes, 40
`inclinations, and contours of the bottom and underlying strata
`in the area. Even then the records obtained are frequently
`limited and inaccurate and .present difficult problems in the
`coordination and rec6nciling thereof. Typical methods and
`equipment heretofore suggested for usc in marine seismic sur- 45
`veying are those shown and described in the following U. S.
`Pats.:
`Paslay
`2,456,696
`Paslay et al.
`2,729,300
`Hersey et al.
`3,065,815
`Loper eta!.· 3,124,781
`Strange
`3,133,262
`Roever
`3,189,870
`In some instances "cross-spread" arrangements of impulse
`generating means and geophones have been used in seismic
`prospecting on land. However, cross spreads in marine areas
`have not heretofore been practical because of the problems of
`handing a main cable of the requisite length, and because of
`the transverse spread required to obtain meaningful results;
`the problems of deploying such an atray and the problems of
`adapting cross spreads to a "continuous profiling" operation.
`Frequent displacement of the elemehts in marine areas with
`respect to each other during the survey and under the in(cid:173)
`fluence of ocean currents, tides, wave motion and other
`forces, as well as the surveying problems of knowing the exact
`location of an intersection of individual profiles, have com(cid:173)
`pounded the above problems.
`
`BRIEF DESCRIPTION OF THE ORA WING
`
`FttG. I is a diagrammatic top plan view of one arrangement
`of impulse producing and echo receiving means embodying
`50 the present invention;
`FIG. 2 is a block diagram illustrating the manner in which
`the 1fquipment of FIG. I is employed;
`FI:G. 3 is a plan view of the block illustrated in FIG. 2;
`F~G. 4 is a diagrammatic illustration of recording equipment
`55 adapted for use in accordance with the present invention;
`F~G. 5 is a view similar to FIG. 4 illustrating a further step in
`the ~ecording of impulses in accordance with the present in(cid:173)
`vention;
`FIG. 6 is a plan view illustrating an alternative arrangement
`60 of the impulse producing and echo receiving means which
`may be employed in the practice of the present invention;
`FIG. 7 is a block diagram similar to FIG. 2 indicating the
`mariner in which the equipment of FIG. 6 operates;
`FIG. 8 is a diagrammatic plan view of a further alternative
`65 arrahgement of elements embodying the present invention;
`FiG. 9 is a diagrammatic illustration of a condition which
`may, be encountered in the prior art;
`·
`FIG. 10 is a plan view of a part of the equipment of the
`70 present invention;
`FIGS. 11 and 12 are side views of alternative embodiments
`of tliat part of the equipment shown in FIG. 10; and
`FIG. 13 is a diagrammatic illustration of one type of control
`system which may be employed in the practice of the present
`75 invention.
`
`SUMMARY OF THE INVENTION
`
`In accordance with the present ihvention, improved and
`more complete records indicating the structural configuration
`in three dimensional space of an area under marine survey arc
`obtained rapidly and accurately by locating and maintaining
`the hydrophones or other echo responsive means at predetcr-
`
`Ex. PGS 1005
`
`

`
`3
`DESCRIPTION OF THE PREFERRED EMBODIMENT
`
`3,581,273
`
`In that form of the invention chosen for purposes of illustra(cid:173)
`tion in FIGS. 1 to S and 13 of the drawings, the surveying
`equipment is moved continuously over an area to be surveyed 5
`by means of a boat or other towing means 2 from which a"(cid:173)
`spread" 4 of hydrophones or other echo responsive. elements 6
`extend rearwardly in a straight line. The hydrophones 6 may
`be of any suitable or preferred type and the spread 4 may be of
`a usual form including from, say, 96 to 120 hydrophones per
`group and comprised of several groups that are connected by
`electrical conductors in cable 10 to a recording equipment 12,
`carried by the boat 2.
`In accordance with the present invention, at least one, and
`preferably two, additional cables 14 and 16 arc towed by the
`boat 2 and as shown in FIG. I, these cables are caused to
`spread outward at opposite sides of cable 10 by means of
`paravanes 18a and 18c respectively. In a similar way, a
`paravane 18b may be connected to the cable 10 of the spread
`4. Each paravane is provided with rudders or other steerable
`means which arc operable to maintain the paravanes in sub(cid:173)
`stantially fixed, or predetermined positions with respect to the
`other para vanes of the assembly. The para vanes 18a, 1811, and
`18c may thus be located and controlled so as to take up posi(cid:173)
`tions which may be a quarter mile or more apart and posi(cid:173)
`tioned so as to define a line 22 extending transversely, and
`preferably at right angles, to the cable 10 and at right angles to
`the direction of transverse of the assembly over the area under
`survey.
`Each of the paravanes 18a, 18b and 18c may be con(cid:173)
`structed, as shown diagrammatically in FIG. 13, so as to posi(cid:173)
`tion, or be provided with, an echo responsive element,
`designated 6, and also to position or be provided with an im(cid:173)
`pulse generating device, designated at 24. For purposes of il(cid:173)
`lustration and discussion it is hereafter indicated that each
`paravane 18a, 18b and 18c has an echo responsive element 6
`and an impulse generating device 24 carried thereby. The im(cid:173)
`pulse generating devices may be of any suitable or preferred
`type such as a gun for exploding gas or other combustible
`charges, or a device for producing an electric arc, or striking
`an anvil and if-desired, the impulse generating device may be
`allowed to drift along its cable to the paravane thereon to
`cause ir to be actuated. However, for most purposes, it is
`preferable to actuate the impulse generating devices and to
`receive the reflected or echo responses by means of ele<.:trical
`connections through cables 10, 14 and 16. In any event, the
`present invention employs an arrangement wherein the echo
`responsive elements arc located at fixed or predetermined
`points spaced apart in two directions within a substantially
`horizontal plane above the area under survey whereas the im(cid:173)
`pulse generating devices are located at one or more spaced
`and predetermined points with respect to at least some of the
`echo responsive elements to establish an effective "cross(cid:173)
`spread" arrangement of the elements which may be moved
`continuously over the area under survey in carrying out the
`survey.
`As shown by way of illustration in FIGS. 1, 2 and 3, the
`equipment may be· towed along a survey line 26 by a boat 2
`floating on the surface 28 of the ocean or other body of water.
`For simplicity of presentation, the area under survey is
`represented as overlying a single seismic interface 30 includ(cid:173)
`ing an upthrown block 32, a transverse fault plane 34, and a
`down thrown block 36, all of which are located some distance
`below the ocean floor 20. The spread of echo responsive ele(cid:173)
`ments 6 on cable 10 extend in a straight line behind the boat 2
`and are held on the survey line 26 by the paravane 18b,
`whereas cables 14 and 16 are caused to spread out laterally
`from the cable 10 by the paravanes 18a and 18c until they are
`spaced apart a distance of, say one-quarter to one-half mile, or
`sufficient to permit separate recording of echoes from points
`in the area under survey which are spaced apart transversely
`of the line of transverse without confusion or suppression of
`such echoes in the records produced. When the cables and
`
`20
`
`25
`
`4
`paravanes, with their impulse generating devi!;es and ec~o
`responsive elements are thus deployed, the imp.Jtsc generating
`devices arc fired in a predetermined manner to 'obtain a set of
`records from the echo responsive means.
`In a typical operation, the impulse generating devices 24 as(cid:173)
`sociated with the paravanes 18a, 18b and 18c may be actuated
`one after the other in a known sequence with a delay between
`the shots as the spread is moved over the area under survey.
`The delay between successive impulses need only be about I
`I 0 to I 0 seconds or sufficient to prevent confusion in the records
`as to which generating devices 24 produce a given trace on the
`recording equipment 12. This is effected through the coor(cid:173)
`dination of the firing circuit control device 13 and the record(cid:173)
`ing equipment 12. Thus, the device 24 associated with the
`15 paravane 18b located on or adjacent cable 10 may be
`detonated or otherwise actuated to produce elastic waves that
`spread downward and outward in all directions. The waves
`represented by the limiting rays40 and 42 are reflected from
`the points 40a and 42a on the seismic interface and are
`received as echoes by the hydrophones 6x and 6y respectively
`on cable 10. In this way a record is caused to be produced in
`the conventional manner of the prior art upon an instrument
`44 of the recording equipment 12.
`At the same time, the vertical ray 46 will be reflected from
`the point 46a on the interface and may be received by the
`echo responsive clement 6 which is on or adjacent the
`para vane 18b .. The latter echo responsive element is con(cid:173)
`nected to instrument 44 and additionally to an instrument 48
`30 of the recording equipment 12 by a switch SO and thereby
`serves to produce the central trace 52 on the record of instru(cid:173)
`ment 48 as shown in FIG. 4. In a like manner and at the same
`time, the inclined rays 54 and 56 generated by the device 24
`associated with the paravane ISh will be reflected from the
`35 points S4a and 56a on the seismic interface to the echo
`responsive elements 6 associated with the paravanes 18a and
`18c respectively. The dominant echoes thus reflected will
`serve to produce the two traces 58 and 60 on the record of in(cid:173)
`strument 48 as shown· in FIG. 4. "Normal move-out cor-
`40 rections" for the slant ray path are applied later in the data
`processing phase. When the dominant reflections of the elastic
`waves thus generated by the device 24 of paravane 18b have
`attenuated sufficiently, switch 50 of instrument 48 is opened
`and switch 62 is closed. Shots arc then fired by the impulse
`45 generating devices 24 associated with the paravanes 18a and
`18c respectively and the rays 64 and 66 reflected vertically
`from the points 64a and 66a on the interface serve to actuate
`the echo responsive clements li'i associated with paravanes 18a
`and 18c to cause the additional traces 68 and 70 to be
`50 recorded by the instrument 48 as shown in FIG. 5. Further(cid:173)
`more, if the para vanes 18a and 18c are so closely spaced with
`respect to the desired depth of penetration as to interfere with
`each other, it is then desirable to fire and receive reflections
`from para vane 18a, with sufficient time for attenuation before
`firing at para vane 18c. In any event, the operations of the fir(cid:173)
`ing and recording equipment are so synchronized that the shot
`instants recorded by the traces 52, 58 and 60 first produced on
`the instrument 48 are caused to register with the traces 68 and
`60 70 provided on said instrument by subsequent shots. In this
`way the successive traces are brought into parallelism so as to
`simplify the relating of the various traces with respect to each
`other.
`When such a set of tracings is completed, the switch 62 is
`65 opened and switch 50 is again closed whereby the equipment
`is restored to its original condition for repeating the cycle of
`operations. The cycle is repeated at predetermined intervals
`or as often as desired while the boat 2 and the assembly of im(cid:173)
`pulse generating and responding means travel along the survey
`70 line 26 as shown in FIGS. 2 and 3. Each record produced as
`described above and as shown in FIG. 5, serves to indicate the
`profile and nature of the seismic interface taken on a substan(cid:173)
`tially vertical orthogonal plane passing through the line 22 at
`right angles to the survey line 26 along which the assembly is
`75 towed. The successive records obtained by repeating the cycle
`
`55
`
`Ex. PGS 1005
`
`

`
`3,581,273
`
`15
`
`5
`6
`88. when the reflected energy is sufficiently attenuated or
`of operations correspond to successive vertical sections taken
`when the survey ship has proceeded along its traverse a
`on the line 22a, 22b, 22c, etc. of FIG. 3 and will be spaced
`desired distance. Thus it is possible to carry out repeated cy-
`apart distances lengthwise of survey line 26 which are depcn-
`cles to obtain records of the reflected impulses representing a
`dent upon the speed of travel of the boat 2 and its array of
`sound generating devices and echo responsive elements and 5 plurality in intersecting vertical planes, thereby defining the
`true inclination of the seismic interface of the area under sur-
`the frequency at which the successive cycles are initiated. At
`the same time, the recording instrument 44 serves to produce
`vey, whereas it has heretofore only been possible to determine
`a record of the profile of the seismic interface as represented
`the apparent inclination in two dimensions while making a sin-
`by a vertical plane passing through the cable 10 of the conven-
`gle traverse.
`In a like manner, other two dimensional arrangements of
`tiona! hydrophone spread 4. As a result, the two records ob- 10
`tained indicate profiles at right angles to each other and afford
`sensing elements within a horizontal plane can be provided by
`much more complete information which, in turn, permits
`the use of multiple spreads connected to recording instru-
`more accurate interpretation regarding the seismic interface
`ments for developing three dimensional records of the profiles
`than has been possible of attainment heretofore. Thus the data
`of areas under survey. As shown in FIG. 8, such spreads may
`so obtained permits determination of true inclinations of the
`be arranged in three parallel lines extending parallel to the
`seismic
`interface and
`the azimuth of linear features.
`direction of transverse of the area under survey, and the three
`Moreover, all this information is obtained by a ·single traverse
`records which are obtained can be utilized to establish a three
`of the area under survey whereby much Jess time is required
`dimensional profile or the seismic interface of the area under
`for completing the survey of any desired plot or zone under in- 20 survey.
`In any of the various forms and arrangements employed in
`vestigation.
`the practice of the present invention, it is desirable to establish
`The systematic and coordinated operation of the equipment
`described above may be attained by the use of any suitable or
`and maintain the impulse generating means and the sensing or
`preferred control mechanism, such as that set forth in U.S.
`echo responsive means in fixed and predetermined relative
`Pat. No. 3,065,815 for example. Further, although the equip- 25 positions during the recording operations. This may be
`ment shown and described herein employs analog recording
`achieved to the extent heretofore accomplished in conven-
`on paper, it is well known in the art to employ other recording
`tiona! seismic surveys by the use of conventional paravanes.
`means and methods such as magnetic tape or the like adapted
`However, as shown in FIG. 9, the use of a conventional spread
`for usc in conventional data processing systems.
`of hydrophones, located in a single dimension of a horizontal
`The method of determining and recording the character of a 30 plane, is subject to error due to the set and drift or displace-
`ment of the spread by marine currents at the successive times
`seismic interface may be varied if desired. Thus, for example,
`after recording the dominant reflections resulting from a shot
`when shots or impulses are generated for recording purposes.
`or impulse generated at l8b, the cable 10 can be connected to
`In accordance with a preferred embodiment of the present
`a different recorder and a single shot or "broadside"
`invention it is possible to overcome the foregoing source of
`generated at t8a. The data obtained and recorded as received 35 ·error and to compensate for any deviations of the paravanes,
`elements or devices from predetermined positions. Thus, as
`from the hydrophones of the spread 4 and cable 10 can then
`be electronically processed to give stacked continuous profile
`shown in FIGS. 10, 11 and 12, the cable 90 by which any pur-
`representative of a plane passing nearly vertically through the
`tion of the arrangement of impulse generating and echo
`line 72 from which elastic waves from the source 18a are
`sensing means is supported may be provided with one or more
`reflected to the hydrophones 6 on cable 1o.
`40 paravanes 92 located at suitable points in the assembly. These
`In a similar way, elastic waves may be generated at 18c and
`paravanes are provided with rudders and elevators or other
`reflected to the hydrophones on cable 10 to obtain a record
`steerable means, diagrammatically indicated at 94 in FIG. 11,
`12 and 13. In addition, the paravancs are provided with radar
`representing the seismic interface in a vertical plane passing
`reflectors or the like 96 by which the position of the paravane,
`through the line of reflections 74 of waves passing to the cable 45 and the various elements or devices connected thereto, can be
`10. It will thus be apparent that the equipment disclosed in
`established and maintained. For this purpose, as represented
`FIGS. 1 to 5 is capable of being used in various ways.
`in FIG. 13, a radar control means 98 carried by the towing
`It is also possible to present the echo responsive elements in
`ship is arranged to respond to signals reflected from the radar
`various arrangements extending in two directions within a
`reflector 96 on the para vane. The responses thus obtained are
`horizontal plane above the surface of the area under survey.
`50 utilized as correction factors and are transmitted to a steering
`Thus as shown in FIGS. 6 and 7 • the boat 2 may be used to tow
`motor 100 through cable 102 to actuate the steering motor
`a longitudinal spread 4 of hydrophones 6 secured to a cable
`100. In this way, the various paravanes may be controlled to
`10. A cross or transverse spread may then be used and em-
`maintain them in predetermined and accurate positions with
`body a cable 80 having hydrophones 82 carried thereby. The
`respect to each other. The seismic means are thereby held in
`cross spread is preferably maintained in a position at right an- 55 such consistent and related positions during traverse of the
`area under survey that the records obtained will be capable of
`gles to the longitudinal spread 4 by paravanes 8la and 8lc and
`if desired intermediate connectors 86 may be employed. The
`ready and accurate correlation and interpretation.
`cable 80 of the cross spread is connected to the recording
`The mechanical and electrical devices employed in the
`equipment on the boat 2 by electrical cables 84.
`para vane control equipment illustrated in FIG. 13 may be of
`When using the arrangement shown in FIG. 6, a single im- 60 any conventional type known in the industry and exemplified
`by those shown and described in U.S. Pat. Nos. 2,960,960;
`pulse generating device 88 may be used and as shown in FIG.
`7, the impulse generator may be located at the intersection of
`2,997,689 and 3,125,980. In a similar way, the recording in-
`the two spreads 4 and 80 or at any other point spaced horizon-
`struments represented in FIGS. 4 and 5 may be any of those
`tally from multiple points on the two cable spreads. The elastic
`known and conventional types now employed or acceptable in
`waves generated at 88 travel downwardly and outwardly and 65 the art of seismic recording and surveying equipment.
`It will thus be apparent that the various elements and com-
`are represented by their limiting recordable ray paths, 83, 85,
`87 and 89. The rays are reflected from seismic interface 30 at
`binations employed in the practice of the present invention
`points 83a, 85a, 81a and 89a and detected by the hydrophones
`are capable of many variations and changes in the application
`at the distal ends of seismic cables 4 and 80. Elastic waves
`thereof. For example, the present invention may be used in ac-
`reflected at the intersection of nearly vertical planes through 70 curately charting the ocean floor or for locating submerged
`bodies. In view thereof, it should be understood that the par-
`seismic cables 4 and 80 with the seismic interface 30 and con-
`tained within the points 83a, 85a, 81a and 89a are detected by
`ticular embodiments of the invention shown in the drawings
`and described above are intended to be illustrative only and
`hydrophones 6 and 82. Data obtained from cables 4 and 80 is
`transcribed by conventional means on separate recorders and
`are not intended to limit the scope of the invention.
`the cycle is repeated with the generation of another impulse at 75
`I claim:
`
`Ex. PGS 1005
`
`

`
`3,581,273
`
`8
`means responsive to deviation of said position indicating
`means from said predetermined position are connected to said
`actuating means to correct such deviation.
`8. Equipment as defined in claim 6 wherein said vehicle
`means include paravanes having rudders and provided with
`signal reflectors connected thereto, a source of signal impul(cid:173)
`ses, and rudder actuating means responsive to deviation of
`said signal reflectors from predetermined positions with
`respect to said source of signal impulses to correct such devia-
`tion.
`9. Equipment as defined in claim 1 wherein a plurality of
`spaced impulse generating devices are provided, and means
`are employed for successively actuating the same.
`10. Equipment as defined in claim 9 wherein means are pro(cid:173)
`vided for actuating said impulse generating devices succes(cid:173)
`sively to produce a separate record of the impulses received
`by said echo responsive clements from each of said impulse
`generating devices.
`11. Equipment as defined in claim 10 wherein means are
`provided for successively producing sets of records, each of
`which sets includes a record of of the echoes received by said
`echo responsive clements following the generation of an im(cid:173)
`pulse by each of said impulse generating device.
`12. A method for conducting marine seismic exploration
`25 comprising the steps:
`providing a plurality of echo responsive clements;
`arranging the echo responsive clements into a horizontally
`extending array, with the clements disposed in predeter(cid:173)
`mined space relationship with respect to each other in
`two directions within the horizontal plane;
`towing the array of echo responsive elements over a surface
`to be explored by means of a vessel;
`maintaining the predetermined space relationship of the
`echo responsive elements by vehicle means; and
`maneuvering the.vehicle means to correct any deviations of
`the positions of the echo responsive elements of the
`predetermined spaced relationship thereof.
`13. The method as defined in claim 12 wherein a plurality of
`impulse generating· means are employed and are actuated at
`successive intervals to produce a set of records indicating the
`characteristics of the area under survey in an orthogonal plane
`substantially normal to the predetermined direction of move(cid:173)
`ment over said area.
`
`35
`
`40
`
`7
`I. Equipment for use in marine seismic surveying, including
`a plurality of echo responsive clements; a vessel for towing
`said echo responsive elements; vehicle means associated with
`said echo responsive elements to maintain said echo respon(cid:173)
`sive elements in a predetermined array, wherein said elements 5
`are spaced apart in two directions in a generally horizontal
`plane; said vehicle means operable to correct the positions of
`said echo responsive elements in response to signals trans(cid:173)
`mitted between said vessel and said vehicle means; at least one
`impulse generating device located in a predetermined position I 0
`with respect to said array and spaced apart in two directions
`from at least a portion of said echo responsive clements; and
`means for separately recording the echoes of each impulse
`generated by said device and received by said echo responsive
`elements as the separately resolved dominant reflections from IS
`points located in two distinct planes disposed at an angle to
`each other and positioned substantially vertically with respect
`to said horizontal plane.
`2. Equipment as ·defined in claim 1 wherein said echo
`responsive elements are arranged in at least two substantially 20
`straight lines in said common horizontal plane.
`3. Equipment as defined in claim 1 wherein said echo
`responsive clements arc arranged in two straight lines extend-
`ing substantially at right angles to each other in said common
`horizontal plane.
`4. Equipment as defined in claim 1 wherein said echo
`responsive means arc located in at least two parallel rows ex(cid:173)
`tending longitudinally of the direction of traverse of the area
`