Geodetic slip rate estimates in California, and their uncertainties

Eileen L. Evans

Submitted August 10, 2016, SCEC Contribution #6606, 2016 SCEC Annual Meeting Poster #147

Current understanding of the seismic potential of faults in California is limited in part by our ability to resolve spatial and temporal changes in fault slip rates across the Pacific-North American plate boundary, and quantify their uncertainties. Fault slip rate can be estimated by modeling fault systems, based on space geodetic measurements of surface ground displacement (GPS and InSAR). However, models that include elastic deformation due to locked faults require fault geometries to be prescribed, and geodetic slip rate estimates may vary widely due to measurement and epistemic (model) uncertainties. To examine published geodetic slip rate estimates in California and quantify variability among models, we compile 31 published geodetic slip rate studies in California and Nevada. Because deformation models may vary in the number of faults represented and the precise location of faults, we combine published geodetic slip rate estimates on a georeferenced grid and compare models spatially. Within each grid cell, a number of metrics are considered based on the suite of fault slip rates in the cell. These metrics include geometric moment (potency), strain and rotation, and variation among models. This approach assumes that all published geodetic slip rate estimates are equally valid, and therefore this variability among models serves as a proxy for epistemic uncertainties in geodetic slip rates: we find an average standard deviation in potency rate of 1.5×10^6 m^3⁄yr for cells of 725 km^2 (1,365 cells), which corresponds to ~2 mm/yr of model uncertainty on a given slip rate. These uncertainties may be incorporated into hazard estimates, enable rigorous comparison with geologic slip rates, and used to systematically identify regions that may require more careful consideration in terms of modeling available geologic and geodetic data.

Key Words
uncertainty, geodetic slip rate

Citation
Evans, E. L. (2016, 08). Geodetic slip rate estimates in California, and their uncertainties. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Tectonic Geodesy