Imaging Patterns of Fault Creep: Implications for Earthquakes on the Hayward Fault

The slip deficit that accumulates on a fault constrains the potential slip (and moment) for subsequent earthquakes on the fault. Fault creep will reduce the rate at which this slip deficit accumulates, at least on those patches of the fault that undergo such aseismic slip. Mapping the spatial and temporal patterns of such creep then becomes an important component of assessments of earthquake potential on a fault such as the Hayward. In regions where faults are creeping at or near the surface, the pattern of surface deformation can be used to constrain fault creep in the upper few kilometers. Determination of the patterns of creep on deeper sections of a fault is poorly constrained by near-fault surface observations. The inclusion of micro-seismicity in analyzing patterns of fault creep adds an additional constraint on locations of locked and creeping patches on the fault. A second consideration in assessing the accumulation of slip deficit is the potential for timedependent creep behavior – particularly driven by post-earthquake viscous relaxation. We are investigating the potential role of such transient behavior in both biasing observations of creep rate, and also modifying the rate at which slip deficit accumulates. Including the effects of a simulated 1868-like earthquake in our models of Hayward Fault creep indicate a significant variations in both the spatial pattern and rate of fault creep during the first 50-100 years after the earthquake