A Method for Using Laboratory Measurements of Electrical and Mechanical Properties to Assist in the Interpretation of Field Data from Shallow Geophysical Measurements

Abstract

In this study, simulations were done to study the interpretation of synthetic field data generated from laboratory measurements for seismic and electrical properties. Synthetic seismic and electrical properties were used to investigate whether using two independent data sets would improve underground imaging of the shallow subsurface. Laboratory measurements consisted of (1) compressional-wave travel times measured at pressures appropriate for the shallow subsurface and (2) electrical impedance with fluid salinities analogous to groundwater. The key elements of this approach were the availability of laboratory measurements for ultrasonic velocities at low pressures in unconsolidated materials and for electrical impedance in similar samples. An inversion code was developed to reconstruct the soil distribution in the shallow subsurface from compressional-wave velocity [Formula: see text] and conductivity [Formula: see text] data. This code minimized the misfit between the observed (simulated field data) [Formula: see text], [Formula: see text] pairs of data, and [Formula: see text] and [Formula: see text] for known soil compositions in the region of interest. Shallow soil distributions reconstructed from seismic and electrical data provided reliable reconstructions of the subsurface. The results showed that the availability of both types of data (seismic and electric) for this work reduced the ambiguity when compared to results using only one data set.