Descr: As part of an interdisciplinary project that aims to study the link between the physical characteristics of hydrothermal systems and the biota that occupy those systems, we have begun a detailed geophysical characterization of the Borax Lake hydrothermal area located near the center of Alvord Valley in the basin and range province of southeast Oregon. Basement rock is comprised of Miocene volcanic deposits overlain by up to 700 m of unconsolidated alluvium. We are conducting seismic investigations on both a basin scale, to place the hydrothermal system in a larger geologic context, and a local high resolution scale for detailed imaging of fault architecture and hydrothermal flow paths. Our initial feasibility study, conducted in the summer of 2002, showed that the hydrothermal area is fault controlled. Initial seismic source tests indicate that the area is well suited to high resolution seismic investigation with clear reflections as deep as 300 ms and frequency content up to 500 Hz. Walk-away gathers show that the fluid distribution near the hot springs is complex with sharp gradients in the piezometric surface. During this years field season, we plan to acquire a high-resolution, 3D seismic survey that spans several of the hot springs. The primary objective of this survey is to produce a detailed image of the fault architecture in an effort to understand flow within the hydryothermal system.
