Imaging Faults with Reverse-Time Migration for Geothermal Exploration at Jemez Pueblo in New Mexico

Abstract

The fault zones may dominate the flow paths of hot water, or confine the boundaries of the geothermal reservoir. Therefore, it is crucial to clearly image the geometry of these fault zones for geothermal exploration. We use reverse-time migration with a wavefield-separation imaging condition to image the fault zones at the Pueblo of Jemez in New Mexico. The migration imaging employs a finite-difference full-wave equation method with a perfectly- matching-layer absorbing boundary condition for backward propagation of seismic reflection data from receivers and forward propagation of wavefields from sources. In the imaging region, we separate the wavefields into the upgoing and downgoing waves, and the leftgoing and rightgoing waves. We utilize the upgoing and downgoing waves to obtain the downward-looking image, and the leftgoing and rightgoing waves to form the left-looking image and right-looking image from sources. The left-looking and right-looking migration results contain the images of the fault zones. These images are normally weaker than downwardlooking images because the reflections from steep fault zones are much weaker than those from sedimentary layers. We apply our reverse-time migration with a wavefield-separation imaging condition to seismic data acquired at the Pueblo of Jemez. Our imaging results reveal many faults in the area, some of which were overlooked before.