Analytical and Data Processing Techniques for Interpretation of Geophysical Survey Data with Special Application to Cavity Detection.

摘要

Results are presented of an effort directed toward the improvement of geophysical data acquisition, processing, and interpretation. Much of the discussion centers around the adaptation of existing or the development of new computer programs and their methodologies for processing and interpreting data acquired from electrical resistivity, microgravity, and seismic methods. Three programs for processing and interpreting electrical resistivity are discussed: (a) RESDIR computes the apparent resistivity as a function of electrode spacing for a given model of vertical subsurface resistivity variations; (b) RESINV calculates the model of vertical subsurface resistivity variation given the apparent resistivities acquired in the field; and (c) RESDAT is a general purpose resistivity program which handles data acquired from horizontal profiling and vertical sounding surveys. Three programs used in conjunction with microgravity surveys are documented: (a) TIDES computes the theoretical variation in gravity caused by earth tides at any location; (b) TALGRAD calculates gravity and gravity-gradient profiles across two-dimensional subsurface models; and (c) HILBERT computes the Hilbert transform which is used to determine the vertical velocity gradient. Two gravity methodologies presented describe: (a) a technique which reduces errors in microgravity surveying through use of optimal gravity station schemes, and (b) the use of polynomial surface fitting for determination of the required field component from a set of data.