The San Jacinto fault is one of the most active branches of the San Andreas system in southern CA, and it consists of multiple segments that exhibit considerably different properties and behaviors both at the surface and at depth. As such, it provides an excellent natural laboratory for studying the mechanics, architecture and evolutionary behavior of a young evolving plate boundary. The goal of this project is to provide improved quantitative understanding of brittle and aseismic deformation processes at a rapidly deforming plate boundary, by linking high-quality in-situ geological, geodetic and seismological data from the San Jacinto fault zone with theoretical analyses. We conducted interdisciplinary observational studies of structural properties, earthquake source and geodetic deformation at various scales, as they relate to fault dynamics and the plate boundary tectonics in southern CA. Several distinct fault sections exist in the observation area with markedly different structural properties, slip-rates, earthquake behavior and locking depths. This diversity will enable us to perform comparative investigations of deformation processes and fault zone properties within a relatively small geographical area. Theoretical studies of dynamic ruptures and coupled evolution of earthquakes and fault structures will aid the interpretation of the observational results. The studies address several fundamental questions including:
How are properties of the fault zone at the surface (e.g., width, internal architecture, segmentation)correlated with those at depth, and what do the results imply with respect to fault evolution?
How are potential zones of large earthquake ruptures related to surface geodetic deformation,spatio-temporal seismicity patterns, non-volcanic tremors, locking depths, and fault zone properties at depth (e.g., seismic velocity, attenuation and anisotropy)?
What are the relationships between material and geometrical properties of the fault zone andearthquake source properties (e.g., spectral content, moments, stress drops, radiated energy, univs. bi-lateral propagation, rupture velocity) at different locations?
What are the properties of the crust around the San Jacinto fault zone and what is the nature of the transitions between fault zone segments, the surrounding blocks, and upper mantle?
What is an appropriate methodology for integrating different types of data on fault zone and crustal properties (with different resolutions and spatial scales) in terms of a self-consistent physical model for the evolution of earthquakes, fault structures and related deformation fields?