San Andreas Fault System Deformation and Stress Evolution (1600-2022)
400-year earthquake cycle deformation and stress evolution simulation of the San Andreas Fault System (version 1). This simulation demonstrates horizontal (east-west and north-south) and vertical plate boundary surface velocity (left three panels) and Coulomb stress accumulation (right panel) throughout the earthquake cycle. Both velocity and stress accumulation are based on a geodetically-constrained interseismic deformation model and slip from 100+ historical and prehistorical earthquake ruptures (~M>6.0) spanning the past 420 years from new paleoseismic constraints (Scharer and Yule, 2020). A wrapped color bar is superimposed on the background velocity models to indicate coseismic (earthquake) events, where the displacements per year far exceed the interseismic rates. In the stress model, the color scale is saturated at 3 MPa to emphasize significant regions of accumulated stress at seismogenic depths. The model also assumes complete stress release following each prescribed earthquake. The North American-Pacific plate boundary is modeled as a series of vertical connected faults embedded in an elastic plate overlying a viscoelastic half-space (Sandwell and Smith-Konter, 2018; Ward et al., 2021). The 4-dimensional model simulates interseismic strain accumulation, coseismic displacement, and post-seismic viscous relaxation of the mantle. Long-term slip rates (i.e. over many earthquake cycles) are constrained to match contemporary geodetic estimates of far-field slip. Deep slip along these faults drives the secular interseismic crustal block motions. The block boundaries are locked from the surface down to a variable locking depth, which is also tuned to match the present-day GNSS measurements. Apparent locking depths range between 0 and 26 km. Stress varies as a function of observation depth within the seismogenic zone; in this simulation, we calculate the representative stress at 1/2 of the local locking depth.