INVER2DBASE-A program to compute basement depths of density interfaces above which the density contrast varies with depth

Abstract

A computer program to invert the gravity anomalies of density interfaces above which the density contrast varies with depth, is presented. The sediment-basement interface is approximated by an N-sided polygon. A function subprogram GR2DPOL and two subroutine subprograms ZOR2DPOL and SIMEQ support the main program. Subroutine ZOR2DPOL calculates the initial depth estimates of a density interface at all anomaly points on the principal profile using the infinite slab approximation. Function subprogram GR2DPOL computes the theoretical gravity anomaly of a density interface at each anomaly point on the profile and returns to the main program. Subroutine SIMEQ is used to solve n incremental depth parts of the vertices of a density interface. Partial derivatives are calculated by a simple finite-difference method. Normal equations are constructed and solved by Marquardt's algorithm. The proposed inversion scheme is independent on the equal station spacing criteria. The validity of the algorithm is demonstrated by calculating the basement depths of the Tucson basin, southern Arizona. © 2001 Elsevier Science Ltd. All rights reserved.