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

A computer program to invert the gravity anomalies of density interfaces ab ove which the density contrast varies with depth, is presented. The sedimen t-basement interface is approximated by an N-sided polygon. A function subp rogram GR2DPOL and two subroutine subprograms ZOR2DPOL and SIMEQ support th e 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 s olve n incremental depth parts of the vertices of a density interface. Part ial derivatives are calculated by a simple finite-difference method. Normal equations are constructed and solved by Marquardt's algorithm. The propose d inversion scheme is independent on the equal station spacing criteria. Th e validity of the algorithm is demonstrated by calculating the basement dep ths of the Tucson basin, southern Arizona. (C) 2001 Elsevier Science Ltd. A ll rights reserved.