Rapid screening approach for cavity detection using surface-based seismic measurements.

摘要

A rapid screening method for detection of shallow cavities using surface-based seismic waves has been developed and documented. Emphasis is placed on seismic surface waves due to their ease of measurement and dispersive nature in heterogeneous media.; The study includes a numerical experiment, field experiments, and an analytical study of data collected for buried voids. Multi-channel and two-channel data acquisition technology are explored. An alternative analysis of the data based on impulse response is investigated. The field experiments were conducted at sites with known natural caves, buried barrels, and earth fissures. Two historic data sets were used. The numerical experiment was performed for a cavity buried in a homogeneous medium.; Based on results of field and numerical experiments a new constant-offset method for rapid cavity detection is proposed. Parameters introduced include detection index, normalized receiver spacing, and normalized wavelength. All steps in data reduction are combined into one single automated process. Trends observed in the experimental data match the numerical data well and most of the targets were identified; thus the algorithm was validated. Optimal testing configurations, including source configuration, minimum and maximum receiver spacings and offset are proposed.