UC San Diego

The Transverse Ranges of California is an active fold-and-thrust belt and has produced some of the most destructive earthquakes in Southern California. Understanding the subsurface structure has both scientific and societal importance, in particular for earthquake hazard assessments. The diverse set of conflicting structural models, specifically in the Western Transverse Ranges, highlights the lack in understanding of the fault architecture in the subsurface. This Thesis presents a new structural model for the Western Transverse Ranges, a test of the model predictions against GPS measurements, and an advancement of the understating of the subsurface structure, evolution and slip rates in the Central Transverse Ranges. After the full range of available observations was compiled we applied structural forward modeling using Trishear to match the observed structure and the interpreted evolution. The first chapter describes modeling of the Western Transverse Ranges since the Pliocene as a southward propagating imbricate thrust system. The second chapter presents a refinement of the model in chapter one, which was accomplished by comparing of a series of kinematic model predictions against GPS measurements in order to narrow the estimated range of dips for the deep part of the fault system. This is also the first time a structural model for the entire Western Transverse Ranges incorporates the full range of geological and geophysical data and observations. The third chapter presents the structural evolution of the Sylmar basin in the highly populated area of San Fernando Valley, northern Los Angeles county. The chapter presents an argument for lowering the estimated slip rate of the Santa Susana fault and distributing it to the faults that are located farther south. The structural understanding as developed by this thesis can help to improve the earthquake risk assessments in the Transverse Ranges.