High-resolution seismic reflection to improve accuracy of hydrogeologic models in Ventura County, California, USA

摘要

A high-resolution seismic-reflection investigation mapped reflectors and identified characteristics influencing the hydrogeol-ogy underlying a portion of the Oxnard Plain in Ventura County, California. Design and implementation of this study was heavily influenced by high levels of cultural noise from vehicles, power lines, roads, manufacturing facilities, and underground utilities/ vaults. An abundance of very high quality reflections within the optimum window on shot gathers allowed accurate velocity analysis and statics corrections, which resulted in consistent and coherent common-midpoint (CMP)-stacked reflections with minimal wavelet degradation. Acquisition and processing flows were tailored to this noisy environment and relatively shallow target interval. Layering within both upper and lower aquifer systems was delineated at a vertical resolution potential of about 2.5 m at 350 m depth. Discontinuities in bedding with significant impact on the groundwater flow, particularly related to saltwater intrusion from agricultural pumping near the coast, were delineated on CMP-stacked sections and correlated to widely separated boring data, thereby providing continuity and realism to hydrologic models.