USGS Open-File Report
Earthquake hazard analysis -- California, Earthquake prediction -- California, Thrust faults (Geology), Subduction zones
This document describes efforts to best characterize seismogenic deformation in and near California. The rate of hazardous earthquakes in California is expected to be proportional to deformation rates; in particular, the rates at which faults slip. Fault slip rates are determined from offsets of geologic and geomorphic features of measured age and by modeling geodetically determined surface displacement rates. Extensive use of geodesy in the form of Global Positioning System (GPS) observations is a new feature brought into the Working Group on California Earthquake Probabilities (WGCEP) forecasts for the Uniform California Earthquake Rupture Forecast, version 3 (UCERF3) model. Geodetic measurements are potentially more spatially comprehensive than geologic offset observations, which can be clustered. Applying either type of data is subject to considerable uncertainty. Geologic observations have dating and other measurement errors, and they often must be extrapolated long distances on fault sections. However, geodetic observations require a modeling step to translate them into estimates of fault slip rate, and they have poor resolution on closely spaced, locked faults. Details about fault slip rates from geologic offsets are presented in appendix B (this report). In this appendix we look at three deformation models that use geologic and geodetic constraints and compare/contrast them with the UCERF3 geological model and the UCERF2 deformation model. We present models, results, and evaluation for their use in the UCERF3 forecast.
Parsons, T., K. M. Johnson, P. Bird, J.M. Bormann, T.E. Dawson, E.H. Field, W.C. Hammond, T.A. Herring, R. McCaffrey, Z.-K. Shen, W.R. Thatcher, R.J. Weldon II, and Y. Zeng, Appendix C—Deformation models for UCERF3, USGS Open-File Report, v. 2013–1165, 66 pp.