Microearthquake monitoring and seismic imaging at The Geysers

摘要

We are monitoring two high-frequency, high-resolution microearthquake networks at The Geysers. The first network consists of 16 stations and is located in the northwest portion of the Geysers. This array is in an area that is representative of a high-temperature, deep, reservoir environment. The second network consists of 13 stations located in the southeast Geysers around the location of the cooperative injection experiment. We are using the data from the networks to compute velocity and attenuation images and earthquake parameters such as precise location and rate and manner of energy release. Our goal is to evaluate the use of this information to manage steam release from geothermal reservoirs. We are supporting this effort with laboratory measurements of velocity and attenuation on Geysers core samples under varying degrees of saturation to help us better interpret our seismic images. To date we find that microearthquake activity follows injection activity, and the dry, low-pressure portions of the reservoir are characterized by low velocity and high attenuation.