UNITED STATES
                             SECURITIES AND EXCHANGE COMMISSION
                                   WASHINGTON, D.C. 20549



                                     FORM 10-K/A
                                   Amendment No. 1

The Issuing Entity is filing this Form 10-K/A to replace Exhibits 31, 33(a)
and 34(a) to the original Form 10-K filed on April 2, 2007. American Security
Insurance Company, Standard Guaranty Insurance Company and TrackSure Insurance
Agency, Inc. (formerly, "Safeco Financial Institution Solutions, Inc.")
("Assurant Inc.") recently provided the Issuing Entity with a revised report on
assessment of compliance with servicing criteria for asset-backed securities
and a related attestation. In the original assessment previously provided to
the Issuing Entity, Assurant Inc. excluded Item 1122(d)(4)(xii) from the scope
of its assessment. Assurant Inc. recently provided the Issuing Entity with a
revised assessment of compliance that assesses Assurant Inc.'s compliance with
Item 1122(d)(4)(xii) and identifies material instance of non compliance with
this criterion. This material instance of non compliance is noted in this Form
10-K/A under "Additional Items Required By General Instruction J." The Issuing
Entity has included this revised assessment of compliance under Exhibit
33(a), the related attestation under Exhibit 34(a) and a revised Rule
13a-14(d)/15d-14(d) Certification under Exhibit 31. This Form 10-K/A does not
otherwise amend the original Form 10-K filed with the Commission on
April 2, 2007.


  (Mark one)

  /X/ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934
      For the fiscal year ended December 31, 2006

      OR



  / / TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934

      For the transition period from                   to



       Commission file number:  333-129480-26

       Thornburg Mortgage Securities Trust 2006-4
       (exact name of issuing entity as specified in its charter)

       Structured Asset Securities Corporation (depositor)
       (exact name of the Registrant as specified in its charter)

       Thornburg Mortgage Home Loans, Inc.
       (exact name of the sponsor as specified in its charter)


  Delaware                                           74-2440850
  (State or other jurisdiction of                    (I.R.S Employer
  incorporation or organization)                     Identification No.)



  745 Seventh Avenue, 7th Floor
   New York, NY                               10019
  (Address of principal executive offices)    (Zip Code)

  Registrant's telephone number, including area code: (212) 526-7000


  Securities registered pursuant to Section 12(b) of the Act:

        NONE.


  Securities registered pursuant to Section 12(g) of the Act:

        NONE.


  Indicate by check mark if the registrant is a well-known seasoned issuer,
  as defined in Rule 405 of the Securities Act.

        Yes  ___     No  X


  Indicate by check mark if the registrant is not required to file reports
  pursuant to Section 13 or Section 15(d) of the Act.

        Yes  ___     No  X


  Indicate by check mark whether the registrant (1) has filed all reports
  required to be filed by Section 13 or 15(d) of the Securities Exchange
  Act of 1934 during the preceding 12 months (or for such shorter period
  that the registrant was required to file such reports), and (2) has been
  subject to such filing requirements for the past 90 days.

        Yes  X       No  ___


  Indicate by check mark if disclosure of delinquent filers pursuant to
  Item 405 of Regulation S-K ( 229.405 of this chapter) is not contained
  herein, and will not be contained, to the best of registrant's knowledge,
  in definitive proxy or information statements incorporated by reference
  in Part III of this Form 10-K or any amendment to this Form 10-K.

                                X


  Indicate by check mark whether the registrant is a large accelerated filer,
  an accelerated filer, or a non-accelerated filer. See definition of
  "accelerated filer and large accelerated filer" in Rule 12b-2 of the
  Exchange Act. (Check one):


  Large accelerated filer ___  Accelerated filer ___  Non-accelerated filer X


  Indicate by check mark whether the registrant is a shell company (as
  defined in Rule 12b-2 of the Act).

        Yes  ___     No  X


  State the aggregate market value of the voting and non-voting common
  equity held by non-affiliates computed by reference to the price at which
  the common equity was last sold, or the average bid and asked price of
  such common equity, as of the last business day of the registrant's most
  recently completed second fiscal quarter.

        Not applicable.


  Indicate by check mark whether the registrant has filed all documents and
  reports required to be filed by Section 12, 13 or 15(d) of the Securities
  Exchange Act of 1934 subsequent to the distribution of securities under a
  plan confirmed by a court.

        Not applicable.

  Indicate the number of shares outstanding of each of the registrant's
  classes of common stock, as of December 31, 2006.

        Not applicable.


     Documents Incorporated by Reference

  List hereunder the following documents if incorporated by reference and
  the Part of the Form 10-K (e.g., Part I, Part II, etc.) into which the
  document is incorporated:  (1)Any annual report to security holders; (2)
  Any proxy or information statement; and (3)Any prospectus filed pursuant to
  Rule 424(b) or (c) under the Securities Act of 1933.  The listed documents
  should be clearly described for identification purposes (e.g., annual
  report to security holders for fiscal year ended December 24, 1980).


        None


                                   PART I
  Item 1.  Business.

            Omitted.


  Item 1A.  Risk Factors.

            Omitted.


  Item 1B.  Unresolved Staff Comments.

            None.


  Item 2.  Properties.

            Omitted.


  Item 3.  Legal Proceedings.

            Omitted.


  Item 4.  Submission of Matters to a Vote of Security Holders.

            Omitted.


                                PART II

  Item 5. Market for Registrants Common Equity, Related Stockholder
          Matters and Issuer Purchases of Equity Securities.

            Omitted.


  Item 6.  Selected Financial Data.

            Omitted.


  Item 7.  Management's Discussion and Analysis of Financial Condition and
           Results of Operations.

            Omitted.


  Item 7A. Quantitative and Qualitative Disclosures About Market Risk.

            Omitted.


  Item 8.  Financial Statements and Supplementary Data.

            Omitted.


  Item 9.  Changes in and Disagreements With Accountants on Accounting and
           Financial Disclosure.

            Omitted.


  Item 9A. Controls and Procedures.

            Omitted.


  Item 9A(T). Controls and Procedures.

            Omitted.


  Item 9B. Other Information.

            None.


                                PART III

  Item 10. Directors, Executive Officers and Corporate Governance.

            Omitted.


  Item 11. Executive Compensation.

            Omitted.

  Item 12. Security Ownership of Certain Beneficial Owners and
           Management and Related Stockholder Matters.

            Omitted.


  Item 13. Certain Relationships and Related Transactions, and Director
           Independence.

            Omitted.


  Item 14. Principal Accounting Fees and Services.

            Omitted.


            ADDITIONAL ITEMS REQUIRED BY GENERAL INSTRUCTION J

  Item 1112(b) of Regulation AB, Significant Obligor Financial Information.

            None.


  Item 1114(b)(2) and 1115(b) of Regulation AB, Significant Enhancement
             Provider Financial Information.



            None.



  Item 1117 of Regulation AB, Legal Proceedings.

            None.



  Item 1119 of Regulation AB, Affiliations and Certain Relationships and
             Related Transactions.

            Information required by Item 1119 has been omitted from this annual
            report on Form 10-K because it is substantially the same information
            as has been provided previously in a prospectus timely filed
            pursuant to Rule 424 promulgated under the Securities Act of 1933
            under the same Central Index Key (CIK) code as this annual report on
            Form 10-K.


  Item 1122 of Regulation AB, Compliance with Applicable Servicing Criteria.


            See item 15 exhibits (33) and (34)

            Assurant, Inc. previously excluded the applicable servicing
            criteria set forth in Item 1122 (d)(4)(xii) from the scope of its
            assessment of compliance. Assurant, Inc. has now assessed its
            compliance with the Applicable Servicing Criteria for the Reporting
            Period of January 1, 2006 through December 31, 2006 and has
            identified a material instance of noncompliance with that servicing
            criterion. Specifically, Assurant, Inc. did not have, during the
            Reporting Period, sufficient policies and procedures to capture the
            information with respect to the Platform Transactions necessary to
            determine compliance with Item 1122(d)(4)(xii). Accordingly,
            Assurant, Inc. has restated its previous assessment for the
            Reporting Period, which excluded evaluation of the criterion,
            to include the criterion and reflect the material noncompliance as
            a result of its assessment.

            The 1122 statements for Wells Fargo Bank, N.A. (servicer) has
            disclosed the following instances of material noncompliance with
            certain servicing criteria applicable to the Company during the year
            ended December 31, 2006:

            1. 1122(d)(3)(i) - Delinquency Reporting - The Company provided
               incomplete data to some third parties who use such data to
               calculate delinquency ratios and determine the status of loans
               with respect to bankruptcy, foreclosure or real estate owned.
               Instead of the actual due date being provided for use in
               calculating delinquencies, the date of the first payment due to
               the security was provided.

            2. 1122(d)(4)(vii) - Notification of Intent to Foreclose - The
               Company, as required by certain servicing agreements, did not
               provide investors with prior notification of intent to foreclose.

            The 1122 statements for Wells Fargo Bank, National Association
            (Corporate Trust Services) has disclosed material noncompliance with
            criterion 1122(d)(3)(i), as applicable to the Company during the
            twelve months ended December 31, 2006.  Certain monthly investor or
            remittance reports included errors in the calculation and/or the
            reporting of delinquencies for the pool assets.

            Although each servicing criterion required by Item 1122(d) of
            Regulation AB is addressed in one or more of the Assessments of
            Compliance with Servicing Criteria and related Attestation Reports
            included with this report, the Servicer's, Cenlar FSB, Assessment
            of Compliance and related Attestation Report did not address each
            of the servicing criteria that the Servicer was required to address
            under the terms of the related Servicing Agreement. The Servicer
            has not identified such failure to provide an Assessment and
            Attestation for these items as a material failure to fulfill its
            obligations under the related servicing agreement in the Servicer's
            Compliance Statement provided under Item 1123 of Regulation AB,
            because the Servicer asserts that those items are not applicable to
            the Servicer.



  Item 1123 of Regulation AB, Servicer Compliance Statement.


            See item 15 exhibit (35)




                                PART IV


  Item 15. Exhibits, Financial Statement Schedules.

   (a) Exhibits

   (4) Trust Agreement dated as of July 1, 2006, among Structured Asset
Securities Corporation, as Depositor, Thornburg Mortgage Home Loans, Inc., as
Seller, Wells Fargo Bank, N.A., as Master Servicer and Securities Administrator,
Wilmington Trust Company, as Delaware Trustee, and LaSalle Bank National
Association, as Trustee and Custodian (incorporated herein by reference from
Exhibit 4.1 of the Current Report on Form 8-K of the registrant, as filed with
the Commission on August 28, 2006).


   (10) Incorporated by reference as Exhibit (4).

   (31) Rule 13a-14(d)/15d-14(d) Certifications.

   (33)  Reports on assessment of compliance with servicing criteria for
         asset-backed securities.



      <TABLE>

      
         <c>
      a) Assurant Inc. as Sub-Contractor for Cenlar, FSB, as Sub-Contractor <F1>
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage <F1>
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A. <F1>
      d) First American Real Estate Solutions of Texas, L.P. as Sub-Contractor for Cenlar, FSB <F1>
      e) JPMorgan Chase Bank, N.A., as Named Servicer <F1>
      f) LaSalle Bank, National Association, as Custodian <F1>
      g) Regulus Group LLC as Sub-Contractor for Wells Fargo Bank, N.A., as Sub-Contractor <F1>
      h) Wells Fargo Bank, N.A., as Servicer <F1>
      i) Wells Fargo Bank, N.A., as Master Servicer <F1>
      j) Wells Fargo Bank, N.A., as Securities Administrator <F1>
      k) ZC Sterling Insurance Agency, Inc. as Sub-Contractor for Wells Fargo Bank, N.A. <F1>

      </TABLE>

     (34) Attestation reports on assessment of compliance with servicing
          criteria for asset-backed securities.

      <TABLE>

      
        <c>
      a) Assurant Inc. as Sub-Contractor for Cenlar, FSB, as Sub-Contractor <F1>
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage <F1>
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A. <F1>
      d) First American Real Estate Solutions of Texas, L.P. as Sub-Contractor for Cenlar, FSB <F1>
      e) JPMorgan Chase Bank, N.A., as Named Servicer <F1>
      f) LaSalle Bank, National Association, as Custodian <F1>
      g) Regulus Group LLC as Sub-Contractor for Wells Fargo Bank, N.A., as Sub-Contractor <F1>
      h) Wells Fargo Bank, N.A., as Servicer <F1>
      i) Wells Fargo Bank, N.A., as Master Servicer <F1>
      j) Wells Fargo Bank, N.A., as Securities Administrator <F1>
      k) ZC Sterling Insurance Agency, Inc. as Sub-Contractor for Wells Fargo Bank, N.A. <F1>

      </TABLE>

     (35) Servicer compliance statement.

      <TABLE>

      
         <c>
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage <F1>
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A. <F1>
      e) JPMorgan Chase Bank, N.A., as Named Servicer <F1>
      h) Wells Fargo Bank, N.A., as Servicer <F1>
      i) Wells Fargo Bank, N.A., as Master Servicer <F1>

      </TABLE>

   (b) Not applicable.

   (c) Omitted.


  <F1> Filed herewith.



                                SIGNATURES

  Pursuant to the requirements of Section 13 or 15(d) of the Securities
  Exchange Act of 1934, the registrant has duly caused this report to be
  signed on its behalf by the undersigned, thereunto duly authorized.



    Thornburg Mortgage Securities Trust 2006-4
    (Issuing Entity)

    Wells Fargo Bank, N.A.
    (Master Servicer)

    /s/ Kristen Ann Cronin
    Kristen Ann Cronin, Vice President
    (senior officer in charge of the servicing function of the master servicer)

    Date: May 27, 2008


  Exhibit Index

  Exhibit No.

   (4) Trust Agreement dated as of July 1, 2006, among Structured Asset
Securities Corporation, as Depositor, Thornburg Mortgage Home Loans, Inc., as
Seller, Wells Fargo Bank, N.A., as Master Servicer and Securities Administrator,
Wilmington Trust Company, as Delaware Trustee, and LaSalle Bank National
Association, as Trustee and Custodian (incorporated herein by reference from
Exhibit 4.1 of the Current Report on Form 8-K of the registrant, as filed with
the Commission on August 28, 2006).


   (10) Incorporated by reference as Exhibit (4).

   (31) Rule 13a-14(d)/15d-14(d) Certifications.

   (33)  Reports on assessment of compliance with servicing criteria for
         asset-backed securities.



      <TABLE>

      
         <c>
      a) Assurant Inc. as Sub-Contractor for Cenlar, FSB
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A.
      d) First American Real Estate Solutions of Texas, L.P. as Sub-Contractor for Cenlar, FSB
      e) JPMorgan Chase Bank, N.A., as Named Servicer
      f) LaSalle Bank, National Association, as Custodian
      g) Regulus Group LLC as Sub-Contractor for Wells Fargo Bank, N.A.
      h) Wells Fargo Bank, N.A., as Servicer
      i) Wells Fargo Bank, N.A., as Master Servicer
      j) Wells Fargo Bank, N.A., as Securities Administrator
      k) ZC Sterling Insurance Agency, Inc. as Sub-Contractor for Wells Fargo Bank, N.A.

      </TABLE>

     (34) Attestation reports on assessment of compliance with servicing
          criteria for asset-backed securities.

      <TABLE>

      
        <c>
      a) Assurant Inc. as Sub-Contractor for Cenlar, FSB
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A.
      d) First American Real Estate Solutions of Texas, L.P. as Sub-Contractor for Cenlar, FSB
      e) JPMorgan Chase Bank, N.A., as Named Servicer
      f) LaSalle Bank, National Association, as Custodian
      g) Regulus Group LLC as Sub-Contractor for Wells Fargo Bank, N.A.
      h) Wells Fargo Bank, N.A., as Servicer
      i) Wells Fargo Bank, N.A., as Master Servicer
      j) Wells Fargo Bank, N.A., as Securities Administrator
      k) ZC Sterling Insurance Agency, Inc. as Sub-Contractor for Wells Fargo Bank, N.A.

      </TABLE>

     (35) Servicer compliance statement.

      <TABLE>

      
         <c>
      b) Cenlar, FSB, as Sub-Servicer for Thornburg Mortgage
      c) Chase Home Finance LLC, as Sub-Servicer for JPMorgan Chase Bank, N.A.
      e) JPMorgan Chase Bank, N.A., as Named Servicer
      h) Wells Fargo Bank, N.A., as Servicer
      i) Wells Fargo Bank, N.A., as Master Servicer

      </TABLE>