Dynamic Rupture Models of Earthquakes on the Bartlett Springs Fault, Northern California

Monday, 15 December 2014
Julian Lozos, Stanford University, Stanford, CA, United States, Ruth Harris, Earthquake Hazards Program Menlo Park, Menlo Park, CA, United States, Jessica R Murray, USGS California Water Science Center Menlo Park, Menlo Park, CA, United States, James J Lienkaemper, USGS Western Regional Offices Menlo Park, Menlo Park, CA, United States and Norman A Abrahamson, Pacific Gas and Electric Company, San Francisco, CA, United States
The Bartlett Springs Fault is a major right-lateral component of the San Andreas fault system in northern California. Fault slip-rate models inferred from GPS data [Murray et al., 2013] and alignment array data [McFarland et al., 2009] both indicate that the Bartlett Springs fault experiences aseismic creep. We use the three-dimensional finite element computer code of Barall [2009] to conduct models of dynamic spontaneous rupture on this fault, both to determine characteristics of potential earthquakes, and to gauge the ability of rupture to propagate in the creeping regions. Within the framework of slip-weakening friction, we represent locked portions of the fault as regions of positive stress drop, and creeping regions as having zero or negative stress drop. Using the fault geometry and creep distribution from studies by Murray et al., we examine simulations that implement either homogeneous initial stresses or a regional stress field, along with several different parameterizations of the contrast in frictional properties between locked and creeping zones. We compare the earthquake source characteristics for the same fault geometry with and without the known creeping sections. These comparisons can be used to estimate the impacts of the creeping sections on ground motion predictions.