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                                                                   EXHIBIT 10.24


                       FOURTH AMENDMENT TO LOAN AGREEMENT

     THIS FOURTH AMENDMENT TO LOAN AGREEMENT (this "Amendment"), dated as of
March 31, 2003, is between CONCORD TECHNOLOGIES, LP, a Texas limited partnership
("Concord"), GEOSPACE ENGINEERING RESOURCES INTERNATIONAL, LP, a Texas limited
partnership ("Engineering"), GEOSPACE TECHNOLOGIES, LP, a Texas limited
partnership, formerly known as Geo Space, LP ("Geo Space"), OYO INSTRUMENTS, LP,
a Texas limited partnership ("Instruments"), and OYOG OPERATIONS, LP, a Texas
limited partnership ("Operations", and together with Concord, Engineering, Geo
Space and Instruments, the "Borrowers"), jointly and severally, and SOUTHWEST
BANK OF TEXAS, N.A., a national banking association ("Lender").

                                    RECITALS:

     A. Geo Space was formerly named Geo Space, LP. On March 5, 2003, Geo Space
changed its name from "Geo Space, LP" to "Geospace Technologies, LP."

     B. Borrowers and Lender entered into that certain Loan Agreement dated as
of February 16, 2001, as amended by First Amendment to Loan Agreement dated as
of February 17, 2001, Second Amendment to Loan Agreement dated as of January 15,
2002 and Third Amendment to Loan Agreement dated as of January 14, 2003 (the
"Agreement").

     C. Pursuant to the Agreement, OYOG, LLC, a Delaware limited liability
company, OYO Geospace Corporation, a Delaware corporation, and OYOG Limited
Partner, LLC, a Nevada limited liability company ("Guarantors"), executed those
certain Guaranty Agreements dated as of January 15, 2002 (the "Guaranty
Agreements"), pursuant to which Guarantors guaranteed to Lender the payment and
performance of the Obligations (as defined in the Agreement).

     D. Borrowers and Lender now desire to amend the Agreement as herein set
forth.

     NOW, THEREFORE, in consideration of the premises herein contained and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

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                                   ARTICLE I.

                                   Definitions

     Section 1.1. Definitions. Capitalized terms used in this Amendment, to the
extent not otherwise defined herein, shall have the meanings given to such terms
in the Agreement, as amended hereby.


                                   ARTICLE II.

                                   Amendments

     Section 2.1. Amendment to Loan Documents. All references to "Geo Space, LP"
contained in each of the Loan Documents are amended to read "Geospace
Technologies, LP".


     Section 2.2. Amendment to Section 9.2. Section 9.2 contained in the
Agreement is amended to read in its entirety as follows:

          Section 9.2. Ratio of EBITDA to Interest Expense. Parent will at all
     times maintain a Ratio of EBITDA to Interest Expense of not less than (a)
     4.00 to 1.00 as of March 31, 2003, (b) 3.00 to 1.00 as of June 30, 2003,
     and (c) 4.00 to 1.00 as of September 30, 2003, and at all times thereafter.
     The Ratio of EBITDA to Interest Expense shall be calculated and tested
     quarterly as of the last day of each fiscal quarter of Parent on a
     cumulative basis (rolling four quarter basis) for the four fiscal quarters
     ended as of the date of calculation.

     Section 2.3. Amendment to Section 9.3. Section 9.3 contained in the
Agreement is amended to read in its entirety as follows:

          Section 9.3. Ratio of Senior Debt to EBITDA. Parent will maintain a
     Ratio of Senior Debt to EBITDA of not greater than (a) 2.75 to 1.00 as of
     March 31, 2003, (b) 7.75 to 1.00 as of June 30, 2003, (c) 4.50 to 1.00 as
     of September 30, 2003, and (d) 2.50 to 1.00 as of December 31, 2003, and at
     all times thereafter. The Ratio of Senior Debt to EBITDA shall be
     calculated and tested quarterly as of the last day of each fiscal quarter
     of Parent on a cumulative basis (rolling four quarter basis) for the four
     fiscal quarters ended as of the date of calculation.

     Section 2.4. Amendment to Exhibits. Exhibit "M" to the Agreement (No
Default Certificate) is amended to conform in its entirety to Annex "B" to this
Amendment.



                                       -2-

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                                  ARTICLE III.

                              Conditions Precedent

     Section 3.1. Conditions. The effectiveness of this Amendment is subject to
the receipt by Lender of the following in form and substance satisfactory to
Lender:

          (a) Certificate - Borrowers. A certificate of the Secretary or the
     Assistant Secretary (or another officer acceptable to Lender) of each
     Borrower certifying resolutions of the board of directors of the General
     Partner as general partner of each Borrower which authorize the execution,
     delivery and performance by each Borrower of this Amendment and the other
     Loan Documents to which such Person is or is to be a party.

          (b) Amendment to Security Agreement-Geo Space. A Second Amendment to
     Security Agreement-Geo Space executed by Geo Space substantially in the
     form of Annex "A" hereto.

          (c) Additional Information. Such additional documents, instruments and
     information as Lender may request.

     Section 3.2. Additional Conditions. The effectiveness of this Amendment is
also subject to the satisfaction of the additional conditions precedent that (a)
the representations and warranties contained herein and in all other Loan
Documents, as amended hereby, shall be true and correct as of the date hereof as
if made on the date hereof, (b) all proceedings, corporate or otherwise, taken
in connection with the transactions contemplated by this Amendment and all
documents, instruments and other legal matters incident thereto shall be
satisfactory to Lender.

                                   ARTICLE IV.

            Agreement, Ratifications, Representations, and Warranties

     Section 4.1. Geo Space's Name Change. Borrowers and Lender agree that
although Geo Space has changed its name from "Geo Space, LP" to "Geospace
Technologies, LP", Geo Space is and remains the same legal entity as it was on
the date of the Agreement, and all of the obligations, covenants and agreements
contained in the Agreement and the Liens created by the Security Agreement-Geo
Space remain in full force and effect, notwithstanding the change of Geo Space's
name.

     Section 4.2. Ratifications. The terms and provisions set forth in this
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Agreement and except as expressly modified and superseded by this
Amendment, the terms and provisions of


                                       -3-

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the Agreement are ratified and confirmed and shall continue in full force and
effect. Borrowers and Lender agree that the Agreement as amended hereby shall
continue to be the legal, valid and binding obligation of such Persons
enforceable against such Persons in accordance with its terms.

     Section 4.3. Representations, Warranties and Agreements. Each Borrower
hereby represents and warrants to Lender that (a) the execution, delivery, and
performance of this Amendment and any and all other Loan Documents executed or
delivered in connection herewith have been authorized by all requisite action on
the part of such Borrower and General Partner and will not violate the
Organizational Documents of such Borrower, (b) the representations and
warranties contained in the Agreement as amended hereby, and all other Loan
Documents are true and correct on and as of the date hereof as though made on
and as of the date hereof, (c) no Event of Default or Unmatured Event of Default
has occurred and is continuing, (d) Borrower is in full compliance with all
covenants and agreements contained in the Agreement as amended hereby, (e)
Borrower is indebted to Lender pursuant to the terms of the Notes, as the same
may have been renewed, modified, extended and rearranged, (f) the liens,
security interests, encumbrances and assignments created and evidenced by the
Loan Documents are, respectively, valid and subsisting liens, security
interests, encumbrances and assignments and secure the Notes as the same may
have been renewed, modified or rearranged and (g) Borrower has no claims,
credits, offsets, defenses or counterclaims arising from the Loan Documents or
Lender's performance under the Loan Documents.

                                   ARTICLE V.

                                  Miscellaneous

     Section 5.1. Reference to Agreement. Each of the Loan Documents, including
the Agreement and any and all other agreements, documents, or instruments now or
hereafter executed and delivered pursuant to the terms hereof or pursuant to the
terms of the Agreement, as amended hereby, are hereby amended so that any
reference in such Loan Documents to the Agreement shall mean a reference to the
Agreement, as amended hereby.

     Section 5.2. Severability. Any provision of this Amendment held by a court
of competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

     Section 5.3. APPLICABLE LAW. THIS AMENDMENT AND ALL OTHER LOAN DOCUMENTS
EXECUTED PURSUANT HERETO SHALL BE DEEMED TO HAVE BEEN MADE AND TO BE PERFORMABLE
IN HOUSTON, HARRIS COUNTY, TEXAS AND SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS.


                                       -4-

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     Section 5.4. Successors and Assigns. This Amendment is binding upon and
shall inure to the benefit of Lender and Borrowers and their respective
successors and assigns, except no Borrower may assign or transfer any of its
rights or obligations hereunder without the prior written consent of Lender.

     Section 5.5. Counterparts. This Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

     Section 5.6. Effect of Waiver. No consent or waiver, express or implied, by
Lender to or for any breach of or deviation from any covenant, condition or duty
by Borrowers shall be deemed a consent or waiver to or of any other breach of
the same or any other covenant, condition or duty.

     Section 5.7. ENTIRE AGREEMENT. THIS AMENDMENT AND ALL OTHER INSTRUMENTS,
DOCUMENTS, AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH THIS
AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES HERETO WITH
RESPECT TO THE SUBJECT MATTER HEREOF AND THEREOF AND SUPERSEDE ANY AND ALL PRIOR
COMMITMENTS, AGREEMENTS, REPRESENTATIONS AND UNDERSTANDINGS, WHETHER WRITTEN OR
ORAL, RELATING TO THE SUBJECT MATTER HEREOF AND THEREOF, AND MAY NOT BE
CONTRADICTED OR VARIED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OR DISCUSSIONS OF THE PARTIES HERETO. THERE ARE NO UNWRITTEN ORAL
AGREEMENTS AMONG THE PARTIES HERETO.

     Executed as of the date first written above.

                                    BORROWERS:

                                    CONCORD TECHNOLOGIES, LP

                                    By:      OYOG, LLC, its general partner

                                       By:      /s/ Thomas T. McEntire
                                          ----------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                                Chief Financial Officer


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                                    GEOSPACE ENGINEERING RESOURCES
                                    INTERNATIONAL, LP

                                    By:      OYOG, LLC, its general partner

                                       By:      /s/ Thomas T. McEntire
                                          ----------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer

                                    GEOSPACE TECHNOLOGIES, LP

                                    By:      OYOG, LLC, its general partner

                                      By:       /s/ Thomas T. McEntire
                                         ------------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer

                                    OYO INSTRUMENTS, LP

                                    By:      OYOG, LLC, its general partner

                                       By:      /s/ Thomas T. McEntire
                                          -----------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer


                                       -6-

<PAGE>

                                    OYOG OPERATIONS, LP

                                    By:      OYOG, LLC, its general partner

                                       By:      /s/ Thomas T. McEntire
                                          -----------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer

                                   LENDER:

                                   SOUTHWEST BANK OF TEXAS, N.A.

                                   By:        /s/ Edward K. Bowdon
                                      ---------------------------------------
                                                 Edward K. Bowdon
                                                  Vice President


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<PAGE>

     Each of the undersigned Guarantors hereby consents and agrees to this
Amendment and agrees that the Guaranty Agreement executed by such person shall
remain in full force and effect and shall continue to be the legal, valid and
binding obligations of such Guarantor, enforceable against such Guarantor in
accordance with its terms and shall evidence such Guarantor's guaranty of the
Notes, as renewed and extended from time to time.

                                    OYOG, LLC

                                    By:        /s/ Thomas T. McEntire
                                       -------------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer


                                    OYOG LIMITED PARTNER, LLC

                                    By:        /s/ Thomas T. McEntire
                                       --------------------------------------
                                                 Thomas T. McEntire
                                                       Manager

                                    OYO GEOSPACE CORPORATION

                                    By:        /s/ Thomas T. McEntire
                                       --------------------------------------
                                                  Thomas T. McEntire
                                                  Vice President and
                                               Chief Financial Officer


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<PAGE>

                                 LIST OF ANNEXES



        Annex         Document
        -----         ---------
          A           Second Amendment to Security Agreement -Geo Space

          B           No Default Certificate


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                                    ANNEX "A"


               Second Amendment to Security Agreement - Geo Space


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                                    ANNEX "B"


                             No Default Certificate

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