Seismic Interferometry Using the Dense Array at the Brady Geothermal Field

Abstract

In March 2016, as part of the Poroelastic Tomography experiment, a large seismic array was deployed over the geothermal field at Brady's Hot Springs in Nevada. This array recorded more than two weeks of continuous data, including several local and regional earthquakes, vibroseis sweeps, and local traffic noise, as well as the ambient seismic wavefield. In this study, we use several methods of seismic interferometry to investigate the site. We focus on three techniques: Shot interferometry uses the energy from the vibroseis sweeps as sources of high frequency energy. Coda interferometry isolates the energy from the scattered wavefield of distant earthquakes. Ambient noise correlation uses the energy of the ambient background field. In each case, the data recorded at one seismometer are correlated with the data recorded at another to obtain an estimate of the Green's function between the two. The 240 geophones, concentrated over a 1.5 square-kilometer area, allow us to calculate nearly 30,000 paths, which we use to characterize the site and measure the localized wavefield.