UC San Diego

This thesis presents research on fault segmentation from regions along the Pacific-North American plate boundary. Geophysical and geological data provide new insights into how fault segments and segment boundaries influence both geohazards and habitat distribution. In the Lake Tahoe basin, Chirp data imaged slide deposits, which could be temporally correlated across multiple basins. The lateral distribution and timing of slide deposits were used to identify seismically triggered slides and reconstruct the paleoseismic history of the basin. The recurrence interval on the basin bounding West Tahoe-Dollar Point Fault is ~3- 4 k.y., and it appears that the fault may sometimes rupture only along individual segments, and other times along the entire length of the fault. Offshore San Diego, geophysical data imaged faulting and deformation in the inner California borderlands geomorphic province. These data highlight changes in major strike slip faults as they approach step overs, define tectonic controls on the topographically high Point Loma peninsula and associated kelp forest, and illustrate that deformation in the borderlands is more consistent with a strike slip model than a regional blind thrust model. Additionally in the region, restraining bends in strike slip faults appear to play an important role in controlling the distribution of methane seep habitats. Localized fluid seepage from a restraining bend in the offshore San Diego Trough Fault hosts a deep-sea methane seep ecosystem that was explored and characterized with ROV surveys and biological sampling. In San Diego Bay, multibeam, backscatter, and Chirp data imaged the pronounced anthropogenic influence on sediments and habitats of San Diego Bay. This study revealed both geologic and anthropogenic influence on eelgrass and kelp forest habitats within the bay, and provided a quantitative baseline for assessing future change due to sea level rise. Understanding geologic controls on habitats over multiple time-scales is important for addressing ecosystem response to climate change and sea-level rise. A study on kelp forest habitat migration over a glacial-interglacial sea level cycle addresses these questions using a new approach with geophysical datasets