The implications of S-wave attenuation in geothermal reservoirs

Abstract

An increasing number of research studies have found that S-waves have significant attenuation and travel time delays as they pass through geothermal reservoirs and magma chambers. For this study, we used a micro-seismic dense array of recording stations to model the underground structure of a geothermal volume and analyzed recorded seismic waves. We analyze waveform data from twenty-five stations and identify whether P- and S-waves have been attenuated. We utilize tomographic solutions of P- and S-wave velocities and derived rock physics parameters, including Bulk, Shear, Lambda, Young's Moduli, and Poisson's ratio, to identify underground geological structures. We speculate the cause of S-wave attenuation and travel time delays. From the rock physics interpretations, the subterranean geothermal reservoir may be further explored to identify fractures, porosity, saturation, and permeability properties. We found that unusually high S-wave attenuation is usually related to a geothermal reservoir zone or magma, and few, if any, earthquakes occur within these zones. We test a rapid, simple, and inexpensive means to provide an early preliminary analysis of geothermal potential.