Imaging complex structure in shallow seismic-reflection data using pre-stack depth migration

In some cases, pre-stack depth migration (PSDM) analysis has the potential to significantly improve the accuracy of both shallow subsurface images, and the measured velocity distribution. Here we present an example of the method taken from the characterization of an active hydrothermal system in the Alvord Basin, southeast Oregon. This work is part of an interdisciplinary project aiming to study the link between the physical characteristics of hydrothermal systems and microbial ecosystems, and includes both basinwide and high-resolution local characterizations of the Borax Lake Hydrothermal System (BLHS). The basin scale seismic survey consists of 11 km of 2D, 30 fold CMP data acquired with a 200 lb accelerated weight drop. PSDM imaging and velocity analysis reveals a complex extensional history with east and west basin segments separated by a mid-basin basement high. This basement high correlates with the northeast trending BLHS. Additionally, the mid-basin fault zone appears to be the location of active deformation suggesting that hydrothermal activity is controlled by both temporal and spatial characteristics of deformation.