We present a nonlinear optimization method for two-dimensional velocity estimation in strongly heterogeneous media. We achieve this by designing a simulated-annealing algorithm to simultaneously maximize reflection coherency as well as minimize first-arrival travel time residuals. Relatively shallow velocity structure is constrained by first-arrival times, while coherency information from deeper reflections (if present) helps constrain deeper […]
The relationships between upper crustal faults, the brittle-ductile transition zone, and underly-ing magmatic features imaged by multifold seismic reflection data are consistent with the hypothesis that the Coso geothermal field, which lies within an extensional step-over between dextral faults, is a young, actively developing metamorphic core complex. The reflection images were processed using a non-linear […]
We employ a Monte Carlo-based optimization scheme called generalized simulated annealing to invert first-arrival times for velocities. We use “dense” common depth point (CDP) data having high multiplicity, as opposed to traditional refraction surveys with few shots. A fast finite-difference solution of the eikonal equation computes first arrival travel times through the velocity models. We […]
The utility of passive seismic emission tomography for mapping geothermal permeability has been tested at two locations in northern Nevada, San Emidio and Crescent Valley. The San Emidio study area overlaps a geothermal field in production since 1987 and also a new, hotter resource recently drilled to the south of the production field. In contrast, […]
