BS in Earth Sciences
Natural Resources Management and Environmental Sciences Department
John J. Jasbinsek
Basin depth is a fundamental parameter in many types of geologic studies such as resource exploration and regional tectonic mapping. The Horizontal-to-Vertical Spectral Ratio (“H/V”) method has been successfully applied to estimating of basin depths up to several hundred meters. In this study the H/V method is applied to the deep basins on the western side of the San Joaquin Valley to determine the thickness of the sedimentary layers and depth to bedrock. Microtremor data from Earthscope Seismic Array stations are ideal to test the accuracy of the H/V method on deeper basins because the data is of high-quality and the proximity of several station locations to where independent basin depth estimates exist. The H/V method is also attractive because it is inexpensive and non-invasive, thus providing a reconnaissance tool for identifying locations in which more detailed mapping techniques may be justified. This study finds that while moderate basin depths (< ~1.2 km) are estimated accurately, deep basin depths (up to ~4 km) are significantly underestimated (~ 29%). These mixed results suggest that the sedimentary to bedrock transition in the deeper parts of the San Joaquin Valley is gradual rather than sharp.