Kinematics and Dynamics of Time-dependent Slip Along the Central Creeping Segment of the San Andreas Fault

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The central, aseismically-slipping segment of the San Andreas fault (CSAF) represents a unique natural laboratory allowing detailed investigations of the kinematics and dynamics of aseismic fault slip. Geodetic and seismic data show that the CSAF behaves in a strongly time-dependent fashion including the occurrence of slow earthquakes, variations of slip rates over several years, and a complex response to regional stress changes. This project (1) characterizes the patterns of aseismic fault slip in space and time to better understand the physics of the underlying fault zone processes, (2) utilizes the sensitivity of slip variations from subtle changes in the regional stress field to better constrain the fault's constitutive properties, and (3) benefits from the sensitivity of aseismic fault slip to the nature of lower crustal deformation to improve our understanding of the rheology of the lower crust. The effort includes an observational program to resolve the kinematics of spatially variable and time dependent fault slip on the CSAF and a theoretical modeling program to allow for interpretation of the slip patterns in the context of fault mechanical processes, fault interaction and rheology. The spatio-temporal kinematics of aseismic fault slip are deduced from space geodetic data spanning the CSAF, from observations of micro-earthquake distribution and activity along the fault, and from analysis of historic deformation data. The kinematic information forms the foundation of an analysis of the dynamics of the CSAF using process-based modeling techniques to address a number of fundamental research problems including (1) the range of behaviors of time dependent aseismic slip, (2) the relationship of slip transients to subtle changes in stress boundary conditions, (3) fault zone constitutive properties, and (4) the rheology of the lower crust reflected in the shallow slip distribution and its longer-term variation in time.