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                                                                    EXHIBIT 4.7


                          FIRST SUPPLEMENTAL INDENTURE



         This FIRST SUPPLEMENTAL INDENTURE, dated as of January 19, 2000 (the
"FIRST SUPPLEMENTAL INDENTURE"), is made and entered into by and between Grant
Geophysical, Inc., a Delaware corporation (the "COMPANY"), the subsidiary
guarantors listed herein (the "SUBSIDIARY GUARANTORS") and LaSalle Bank
National Association, as trustee (the "TRUSTEE"), under an Indenture (the
"INDENTURE"), dated as of February 18, 1998, between the Company, the
Subsidiary Guarantors and the Trustee. All capitalized terms used in this First
Supplemental Indenture that are defined in the Indenture, either directly or by
reference therein, have the respective meanings assigned to them therein,
except to the extent such terms are otherwise defined in this First
Supplemental Indenture or the context clearly requires otherwise.

                                    RECITALS

         WHEREAS, Section 9.2 of the Indenture provides, among other things,
that with the consent of Holders of not less than a majority in aggregate
principal amount of the Outstanding Securities, the Company, when authorized by
a Board Resolutions, each of the Subsidiary Guarantors, when authorized by a
Board Resolutions, and the Trustee upon Company Request may amend or supplement
the Indenture for the purpose of adding any provision to or changing in any
manner or eliminating any of the provisions of the Indenture or of modifying in
any manner the rights of the Holders under the Indenture;

         WHEREAS, the Company has solicited consents from Holders relating to
the matters set forth in this First Supplemental Indenture (the "PROPOSED
AMENDMENT");

         WHEREAS, Holders of a majority in aggregate principal amount of the
Outstanding Securities have consented to the Proposed Amendment; and

         WHEREAS, the Board of Directors of the Company has adopted Board
Resolutions authorizing and approving the Proposed Amendment, and the Company,
the Subsidiary Guarantors and the Trustee are executing and delivering this
First Supplemental Indenture in order to provide therefor.

         NOW, THEREFORE, for and in consideration of the premises, and other
good and valuable consideration, the sufficiency and receipt of which are
hereby acknowledged, it is mutually agreed, for the equal and proportionate
benefit of all Holders, as follows:

                                  ARTICLE ONE
                             AMENDMENT TO INDENTURE

         Section 1.01  Amended Definitions.  The following definitions in
Section 1.1 of the Indenture are hereby amended as follows:

         (a)      The definition of "Affiliate" is hereby amended to read in
its entirety as follows:

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                           "AFFILIATE" means, with respect to any specified
                  Person, any other Person directly or indirectly controlling
                  or controlled by or under direct or indirect common control
                  with such specified Person. For the purposes of this
                  definition, "control" when used with respect to any specified
                  Person means the power to direct the management and policies
                  of such Person, directly or indirectly, whether through the
                  ownership of voting securities, by contract or otherwise; and
                  the terms "controlling" and "controlled" have meaning
                  correlative to the foregoing. For purposes of this
                  definition, beneficial ownership of more than 50% of the
                  voting common equity (on a fully diluted basis) or options or
                  warrants to purchase such equity (but only if exercisable at
                  the date of determination or within 60 days thereof) of a
                  Person shall be deemed to constitute control of such Person.

         (b)      The definition of "Consolidated EBITDA Coverage Ratio" is
hereby amended to read in its entirety as follows:

                           "CONSOLIDATED EBITDA COVERAGE RATIO" means, for any
                  period, the ratio on a pro forma basis of (a) the sum of
                  Consolidated Net Income, Consolidated Interest Expense,
                  Consolidated Income Tax Expense and Consolidated Non-cash
                  Charges deducted in computing Consolidated Net Income, in
                  each case, for such period, of the Company and its Restricted
                  Subsidiaries on a consolidated basis, all determined in
                  accordance with GAAP, to (b) the sum of such Consolidated
                  Interest Expense for such period; provided, however, that (i)
                  the Consolidated EBITDA Coverage Ratio shall be calculated on
                  a pro forma basis assuming that (A) the Indebtedness to be
                  incurred (and all other Indebtedness incurred after the first
                  day of such period of four full fiscal quarters referred to
                  in Section 10.12(a) hereof through and including the date of
                  determination), and (if applicable) the application of the
                  net proceeds therefrom (and from any other such
                  Indebtedness), including to refinance other Indebtedness, had
                  been incurred on the first day of such four-quarter period
                  and, in the case of Acquired Indebtedness, on the assumption
                  that the related transaction (whether by means of purchase,
                  merger or otherwise) also had occurred on such date with the
                  appropriate adjustments with respect to such acquisition
                  being included in such pro forma calculation and (B) any
                  acquisition or disposition by the Company or any Restricted
                  Subsidiary of any Properties outside the ordinary course of
                  business, or any repayment, redemption or extinguishment of
                  any principal amount of any Indebtedness of the Company or
                  any Restricted Subsidiary prior to the Stated Maturity
                  thereof, in either case since the first day of such period of
                  four full fiscal quarters through and including the date of
                  determination, had been consummated on such first day of such
                  four-quarter period, (ii) in making such computation, the
                  Consolidated Interest Expense attributable to interest on any
                  Indebtedness required to be computed on a pro forma basis in
                  accordance with Section 10.12(a) hereof and (A) bearing a
                  floating interest rate shall be computed as if the rate in
                  effect on the date of computation had been the applicable
                  rate for the entire period and (B) which was not outstanding
                  during the period for which the computation is being made but
                  which bears, at the option of the Company, a fixed or
                  floating rate of interest, shall be computed by applying, at
                  the option of the Company, either the fixed or


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                  floating rate, (iii) in making such computation, the
                  Consolidated Interest Expense attributable to interest on any
                  Indebtedness under a revolving credit facility required to be
                  computed on a pro forma basis in accordance with Section
                  10.12(a) hereof shall be computed based upon the average
                  daily balance of such Indebtedness during the applicable
                  period, provided that such average daily balance shall be
                  reduced by the amount of any repayment of Indebtedness under
                  a revolving credit facility during the applicable period,
                  which repayment permanently reduced the commitments or
                  amounts available to be reborrowed under such facility, (iv)
                  notwithstanding clauses (ii) and (iii) of this proviso,
                  interest on Indebtedness determined on a fluctuating basis,
                  to the extent such interest is covered by agreements relating
                  to Interest Rate Protection Obligations, shall be deemed to
                  have accrued at the rate per annum resulting after giving
                  effect to the operation of such agreements, and (v) if after
                  the first day of the period referred to in clause (a) of this
                  definition the Company has permanently retired any
                  Indebtedness out of the Net Cash Proceeds of the issuance and
                  sale of shares of Qualified Capital Stock of the Company,
                  Consolidated Interest Expense shall be calculated on a
                  proforma basis as if such Indebtedness had been retired on
                  the first day of such period.

         (c)      The definition of "Consolidated Interest Expense" is hereby
amended to read in its entirety as follows:

                           "CONSOLIDATED INTEREST EXPENSE" means, for any
                  period, without duplication, (i) the sum of (a) the interest
                  expense of the Company and its Restricted Subsidiaries for
                  such period as determined on a consolidated basis in
                  accordance with GAAP, including, without limitation, (A) any
                  amortization of debt discount, (B) the net cost under
                  Interest Rate Protection Obligations (including any
                  amortization of discounts), (c) the interest portion of any
                  deferred payment obligation constituting Indebtedness, (D)
                  all commissions, discounts and other fees and charges owed
                  with respect to letters of credit and bankers' acceptance
                  financing and (E) all accrued interest, in each case to the
                  extent attributable to such period, (b) to the extent any
                  Indebtedness of any Person (other than the Company or a
                  Restricted Subsidiary) is guaranteed by the Company or any
                  Restricted Subsidiary, the aggregate amount of interest paid
                  (to the extent not accrued in a prior period) or accrued by
                  such other Person during such period attributable to any such
                  Indebtedness, in each case to the extent attributable to that
                  period, (c) the aggregate amount of the interest component of
                  Capitalized Lease Obligations paid (to the extent not accrued
                  in a prior period), accrued or scheduled to be paid or
                  accrued by the Company and its Restricted Subsidiaries during
                  such period and (d) the aggregate amount of cash dividends
                  paid on Preferred Stock or on Disqualified Capital Stock of
                  the Company and its Restricted Subsidiaries, to the extent
                  such Preferred Stock or Disqualified Capital Stock is owned
                  by Persons other than the Company or any Restricted
                  Subsidiary, less (ii), to the extent included in clause (i)
                  above, amortization of capitalized debt issuance costs of the
                  Company and its Restricted Subsidiaries during such period.


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         (d)       The definition of "Permitted Indebtedness" is hereby amended
to read in its entirety as follows:

          "PERMITTED INDEBTEDNESS" means any of the following:

          (i)      Indebtedness (and any guarantee thereof) in an aggregate
                   principal amount at any one time outstanding not to exceed
                   (a) the greater of (x) $50,000,000 at any time outstanding
                   or (y) the sum of 85% of the amount of Eligible Receivables
                   of the Company and its Restricted Subsidiaries and 50% of
                   the amount of Eligible Inventory of the Company and its
                   Restricted Subsidiaries, less (b) any amounts derived from
                   Asset Sales, except for an Asset Sale consisting of a sale
                   of the multi-client seismic data owned by, or gathered for
                   the account of, the Company and applied to the permanent
                   reduction of the Indebtedness under any such credit
                   facilities as contemplated by Section 10.17 hereof (the
                   "Maximum Bank Credit Amount"), and any renewals, amendments,
                   extensions, supplements, modifications, deferrals,
                   refinancings or replacements (each, for purposes of this
                   clause (i), a "refinancing") thereof, including any
                   successive refinancing thereof, so long as the aggregate
                   principal amount of any such new Indebtedness, together with
                   the aggregate principal amount of all other Indebtedness
                   outstanding pursuant to this clause (i), shall not at any
                   one time exceed the Maximum Bank Credit Amount;

          (ii)     Indebtedness under the Original Securities and any
                   Series B Securities issued in exchange for Original
                   Securities of an equal principal amount;

          (iii)    Indebtedness outstanding or in effect on the date of this
                   Indenture (and not repaid or defeased with the proceeds of
                   the offering of the Original Securities);

          (iv)     Indebtedness under Interest Rate Protection Obligations,
                   provided that (1) such Interest Rate Protection Obligations
                   are related to payment obligations on Permitted Indebtedness
                   or Indebtedness otherwise permitted by Section 10.12(a)
                   hereof, and (2) the notional principal amount of such
                   Interest Rate Protection Obligations does not exceed the
                   principal amount of such Indebtedness to which such Interest
                   Rate Protection Obligations relate;

          (v)      Indebtedness under Currency Hedge Obligations, provided that
                   (1) such Currency Hedge Obligations are related to payment
                   obligations on Permitted Indebtedness or Indebtedness
                   otherwise permitted by Section 10.12(a) hereof, or to the
                   foreign currency cash flows reasonably expected to be
                   generated by the Company and its Restricted Subsidiaries,
                   and (2) the notional principal amount of such Currency Hedge
                   Obligations does not exceed the principal amount of such
                   Indebtedness and the amount of such foreign currency cash
                   flows to which such Currency Hedge Obligations relate;

          (vi)     the Subsidiary Guarantees of the Original Securities
                   (and any assumption of the obligations guaranteed thereby);


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          (vii)    Indebtedness of the Company to a Wholly Owned Restricted
                   Subsidiary and Indebtedness of any Restricted Subsidiary to
                   the Company or a Wholly Owned Restricted Subsidiary;
                   provided, however, that upon any subsequent issuance or
                   transfer of any Capital Stock or any other event which
                   results in any such Wholly Owned Restricted Subsidiary
                   ceasing to be a Wholly Owned Restricted Subsidiary or any
                   other subsequent transfer of any such Indebtedness (except
                   to the Company or a Wholly Owned Restricted Subsidiary),
                   such Indebtedness shall be deemed, in each case, to be
                   incurred and shall be treated as an incurrence for purposes
                   of Section 10.12(a) hereof at the time the Wholly Owned
                   Restricted Subsidiary in question ceased to be a Wholly
                   Owned Restricted Subsidiary or the time such subsequent
                   transfer occurred;

          (viii)   Indebtedness in respect of bid, performance or surety bonds
                   issued for the account of the Company or any Restricted
                   Subsidiary in the ordinary course of business, including
                   guaranties or obligations of the Company or any Restricted
                   Subsidiary with respect to letters of credit supporting such
                   bid, performance or surety obligations (in each case other
                   than for an obligation for money borrowed);

          (ix)     Non-Recourse Indebtedness;

          (x)      any renewals, substitutions, refinancings or replacements
                   (each, for purposes of this clause (x), a "refinancing") by
                   the Company or a Restricted Subsidiary of any Indebtedness
                   incurred pursuant to clause (iii) of this definition,
                   including any successive refinancing by the Company or such
                   Restricted Subsidiary, so long as (A) any such new
                   Indebtedness shall be in a principal amount that does not
                   exceed the principal amount (or, if such new Indebtedness
                   being refinanced provides for an amount less than the
                   principal amount thereof to be due and payable upon a
                   declaration of acceleration thereof, such lesser amount as
                   of the date of determination) so refinanced plus the amount
                   of any premium required to be paid in connection with such
                   refinancing pursuant to the terms of the Indebtedness
                   refinanced or the amount of any premium reasonably
                   determined by the Company or such Restricted Subsidiary as
                   necessary to accomplish such refinancing, plus the amount of
                   expenses of the Company or such Restricted Subsidiary
                   incurred in connection with such refinancing, (B) in the
                   case of any refinancing of Indebtedness that is pari passu
                   with or subordinated in right of payment to either the
                   Securities or any Subsidiary Guarantees, then such new
                   Indebtedness is either pari passu with or subordinated in
                   right of payment to the Securities or any Subsidiary
                   Guarantees, as the case may be, at least to the same extent
                   as the Indebtedness being refinanced and (c) such new
                   Indebtedness has an Average Life equal to or longer than the
                   Average Life of the Indebtedness being refinanced and a
                   final Stated Maturity that is at least 91 days later than
                   the final Stated Maturity of the Indebtedness being
                   refinanced; and

          (xi)     any additional Indebtedness in an aggregate principal
                   amount not in excess of $10,000,000 at any one time
                   outstanding and any guarantee thereof.


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         Section 1.02 Section 5.2 of the Indenture. The last paragraph of
Section 5.2 is hereby amended to read in its entirety as follows:

                  No such rescission shall affect any subsequent default or
         impair any right consequent thereon. Notwithstanding the foregoing, if
         an Event of Default specified in Section 5.1(e) hereof shall have
         occurred and be continuing, such Event of Default and any
         consequential acceleration of the Securities shall be automatically
         rescinded if the Indebtedness that is the subject of such Event of
         Default has been repaid, or if the default relating to such
         Indebtedness is waived or cured and if such Indebtedness has been
         accelerated, then the holders thereof have rescinded their declaration
         of acceleration in respect of such Indebtedness (provided, in each
         case, that such repayment, waiver, cure or rescission is effected
         within a period of 30 days from the continuation of such default
         beyond the applicable grace period or the occurrence of such
         acceleration), and written notice of such repayment, or cure or waiver
         and rescission, as the case may be, shall have been given to the
         Trustee by the Company and countersigned by the holders of such
         Indebtedness or a trustee, fiduciary or agent for such holders or
         other evidence satisfactory to the trustee of such events is provided
         to the Trustee, within 30 days after any such acceleration in respect
         of the Securities, and so long as such rescission of any such
         acceleration of the Securities does not conflict with any judgment or
         decree as certified to the Trustee by the Company.

         Section 1.03 Section 8.1 of the Indenture. Section 8.1 of the
Indenture is hereby amended to read in its entirety as follows:


          Section 8.1 Company May Consolidate, etc., Only on Certain Terms.

                  The Company shall not, in any single transaction or a series
         of related transactions, merge or consolidate with or into any other
         Person, or sell, assign, convey, transfer, lease or otherwise dispose
         of all or substantially all the Properties of the Company and its
         Restricted Subsidiaries on a consolidated basis to any Person or group
         of Affiliated Persons, and the Company shall not permit any of its
         Restricted Subsidiaries to enter into any such transaction or series
         of transactions if such transaction or series of transactions, in the
         aggregate, would result in the sale, assignment, conveyance, transfer,
         lease or other disposition of all or substantially all of the
         Properties of the Company and its Restricted Subsidiaries on a
         consolidated basis to any other Person or group of Affiliated Persons,
         unless at the time and after giving effect thereto:

              (a)  (i) if the transaction is a merger or consolidation, the
                   Company shall be the surviving Person of such merger or
                   consolidation, or (ii) the Person (if other than the
                   Company) formed by such consolidation or into which the
                   Company is merged or to which the Properties of the Company
                   or its Restricted Subsidiaries, as the case may be, are
                   sold, assigned, conveyed, transferred, leased or otherwise
                   disposed of (any such surviving Person or transferee Person
                   being called the "Surviving Entity") shall expressly assume
                   by a supplemental indenture to this Indenture executed and
                   delivered to the Trustee, in form satisfactory to the
                   Trustee, all the


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<PAGE>   7

                   obligations of the Company under the Securities and this
                   Indenture, and, in each case, this Indenture shall remain
                   in full force and effect;

              (b)  immediately before and immediately after giving effect
                   to such transaction or series of transactions on a pro forma
                   basis (and treating any Indebtedness not previously an
                   obligation of the Company or any of its Restricted
                   Subsidiaries which becomes the obligation of the Company or
                   any of its Restricted Subsidiaries in connection with or as
                   a result of such transaction or transactions as having been
                   incurred at the time of such transaction or transactions),
                   no Default or Event of Default shall have occurred and be
                   continuing;

              (c)  if the Company is not the continuing obligor under this
                   Indenture, then each Subsidiary Guarantor then in existence,
                   unless it is the Surviving Entity, shall have by
                   supplemental indenture confirmed that its Subsidiary
                   Guarantee of the Securities shall apply to the Surviving
                   Entity's obligations under this Indenture and the
                   Securities; and

              (d)  the Company (or the Surviving Entity if the Company is
                   not the continuing obligor under this Indenture) shall have
                   delivered to the Trustee, in form and substance reasonably
                   satisfactory to the Trustee, (i) an Officers' Certificate
                   stating that such consolidation, merger, conveyance,
                   transfer, lease or other disposition and, if a supplemental
                   indenture is required in connection with such transaction,
                   such supplemental indenture, comply with the requirements
                   under this Indenture and (ii) an Opinion of Counsel stating
                   that the requirements of Section 8.1(a) have been satisfied.

         Section 1.04 Section 10.10 of the Indenture. Section 10.10(a)(iv)(1)
of the Indenture is hereby amended to read in its entirety as follows:

              (1)  50% of the Consolidated Net Income of the Company accrued on
                   a cumulative basis during the period beginning on January 1,
                   2000 and ending on the last day of the Company's last fiscal
                   quarter ending prior to the date of such proposed Restricted
                   Payment (or, if such Consolidated Net Income shall be a loss,
                   minus 100% of such loss), plus

         Section 1.05 Section 1012 of the Indenture. Section 10.12(b) of the
Indenture is hereby amended to read in its entirety as follows:

              (b)  Neither the Company nor any Subsidiary Guarantor shall
                   incur any Indebtedness (other than Permitted Indebtedness)
                   that is expressly subordinated to any other Indebtedness of
                   the Company or such Subsidiary Guarantor, as the case may
                   be, unless such Indebtedness, by its terms or the terms of
                   any agreement or instrument pursuant to which such
                   Indebtedness is issued or outstanding, is also expressly
                   made subordinate to the Securities or the Subsidiary
                   Guarantee of such


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<PAGE>   8
                   Subsidiary Guarantor, as the case may be, at least to the
                   extent it is subordinated to such other Indebtedness.

                                  ARTICLE II
                               GENERAL PROVISIONS

                  Section 2.01.  Effectiveness of Amendment. This First
Supplemental Indenture is effective as of the date first written above.

                  Section 2.02. Ratification of Indenture. The Indenture is in
all respects acknowledged, ratified and confirmed, and shall continue in full
force and effect in accordance with the terms thereof and as supplemented by
this First Supplemental Indenture. The Indenture and this First Supplemental
Indenture shall be read, taken and construed as one and the same instrument.

                  Section 2.03.  Certificate and Opinion as to Conditions
Precedent. Simultaneously  with and as a condition to the execution of this
First Supplemental Indenture, the Company is delivering to the Trustee:

                           (a) an Officers' Certificate (in form and substance
         reasonably satisfactory to the Trustee) stating that, in the opinion
         of the signers, all conditions precedent provided for in the Indenture
         relating to the amendment and supplement of the Indenture have been
         complied with; and

                           (b) an Opinion of Counsel (in form and substance
         reasonably satisfactory to the Trustee) stating that, in the opinion
         of such counsel, all such conditions precedent have been complied
         with.

                  Section 2.04. Effect of  Headings.  The Article and Section
headings in this First Supplemental Indenture are for convenience only and shall
not affect the construction of this First Supplemental Indenture.

                  Section 2.05. Governing Law. THIS FIRST SUPPLEMENTAL
INDENTURE SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE
STATE OF NEW YORK, AS APPLIED TO CONTRACTS MADE AND PERFORMED WITHIN THE STATE
OF NEW YORK, WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW.

                  Section 2.06.  Counterparts.  First Sixth Supplemental
Indenture may  be executed in any number of counterparts, each of which so
executed shall be deemed to be an original, but all such  counterparts shall
together constitute the same instrument.

            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]


                                     -8-

<PAGE>   9

         IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed as of the day and year first above
written.



                                COMPANY:

                                         GRANT GEOPHYSICAL, INC.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                SUBSIDIARY GUARANTORS:

                                         ADVANCED SEISMIC TECHNOLOGY, INC.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         GRANT GEOPHYSICAL CORP.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         GRANT GEOPHYSICAL DO BRAZIL LTDA.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                      -9-

<PAGE>   10

                                         GRANT GEOPHYSICAL (INT'L), INC.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         PT GRANT GEOPHYSICAL INDONESIA



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         RECURSOS ENERGETICOS LTDA.


                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         SOLID STATE GEOPHYSICAL, INC.



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                         SOLID STATE INTERNACIONAL
                                           INGENIERIA, CA.


                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                     -10-

<PAGE>   11

                                TRUSTEE:

                                         LASALLE BANK NATIONAL ASSOCIATION



                                         By:
                                             -------------------------------
                                             Name:
                                             Title:


                                     -11-