65. Field, E. H., G. P. Biasi, P. Bird, T. E. Dawson, K. R. Felzer, D. D. Jackson, K. M. Johnson, T. H. Jordan, C. Madden, A. J. Michael, K. R. Milner, M. T. Page, T. Parsons, P. M. Powers, B. E. Shaw, W. R. Thatcher, R. J. Weldon, II, and Y. Zeng [2013] Unified California Earthquake Rupture Forecast, version 3 (UCERF3)-The time-independent model, U.S. Geol. Surv. Open-File Rep., 2013-1165 (and Cal. Geol. Surv. Spec. Rep. 228, and Southern California Earthquake Center Pub. 1792), 97 pages (main report) + 20 Appendices; http://pubs.usgs.gov/of/2013/1165/;


Parsons, T., K. M. Johnson, P. Bird, J. 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 [2013] Appendix C—Deformation Models for UCERF3.  66 pages.

Also condensed and republished as:

Field, E. H., R. J. Arrowsmith, G. P. Biasi, P. Bird, T. E. Dawson, K. R. Felzer, D. D. Jackson, K. M. Johnson, T. H. Jordon, C. Madden, A. J. Michael, K. R. Milner, M. T. Page, T. Parsons, P. M. Powers, B. E. Shaw, W. R. Thatcher, R. J. Weldon II, and Y. Zeng [2014] Uniform California Earthquake Rupture Forecast version 3 (UCERF3)—The time-independent model, Bull. Seismol. Soc. Am., 104(3), 1122-1180, doi: 10.1785/0120130164.

[Main report] Abstract.  In this report we present the time-independent component of the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which provides authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging earthquakes in California. The primary achievements have been to relax fault segmentation assumptions and to include multifault ruptures, both limitations of the previous model (UCERF2). The rates of all earthquakes are solved for simultaneously, and from a broader range of data, using a system-level “grand inversion” that is both conceptually simple and extensible. The inverse problem is large and underdetermined, so a range of models is sampled using an efficient simulated annealing algorithm. The approach is more derivative than prescriptive (for example, magnitude/frequency distributions are no longer assumed), so new analysis tools were developed for exploring solutions. Epistemic uncertainties were also accounted for using 1,440 alternative logic tree branches, necessitating access to supercomputers. The most influential uncertainties include alternative deformation models (fault slip rates), a new smoothed seismicity algorithm, alternative values for the total rate of M≥5 events, and different scaling relationships, virtually all of which are new. As a notable first, three deformation models are based on kinematically consistent inversions of geodetic and geologic data, also providing slip-rate constraints on faults previously excluded because of lack of geologic data. The grand inversion constitutes a system-level framework for testing hypotheses and balancing the influence of different experts. For example, we demonstrate serious challenges with the Gutenberg-Richter hypothesis for individual faults. UCERF3 is still an approximation of the system, however, and the range of models is limited (for example, constrained to stay close to UCERF2). Nevertheless, UCERF3 removes the apparent UCERF2 overprediction of M6.5–7 earthquake rates and also includes types of multifault ruptures seen in nature. Although UCERF3 fits the data better than UCERF2 overall, there may be areas that warrant further site-specific investigation. Supporting products may be of general interest, and we list key assumptions and avenues for future model improvements.

[Appendix C] Summary. 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.

We identify here two classes of geodetic models for fault slip rate and residual “off-fault” seismogenic deformation: (1) elastic block models and (2) what we call faulted continuum models. Both fit the observed data reasonably well, and are viable representations of California deformation. Generally, the geodetic models give high weight to geologic information and change it only enough to also fit GPS and stress-direction observations. In so doing, they modify the geologic model to be more consistent with the overall relative plate-motion vectors across the Pacific-North American Plate boundary region in California. The faulted continuum models tend, like the geologic model, to have uniform slip along strike for most faults. One block model, called here the average block model because it has resulted from a separate inversion of results from five different techniques, is the model that shows more slip-rate gradients on major faults relative to the other models. We examine the proposed UCERF3 deformation models in the contexts of (1) overall moment rate, (2) fit to GPS observations, (3) fit to geological constraints, (4) fit to relative plate-motion rates and directions, and (5) magnitudes of residual moment rate not on defined faults.

We developed weighting schemes based on the ranking presented in the summary table (table C1) and from expert opinion developed through the UCERF3 Deformation Model Evaluation Committee. There are data-driven differences for slip-rate estimates on important faults like the southern San Andreas such that a range of models based on the geologic and geodetic data can define the deformation rates for use in earthquake rate estimates.

Main report, & Appendices, online at USGS

Archive of input & output files related to my NeoKinema deformation model(s)

Note that the figures shown here are only a selection, emphasizing those relevant to my NeoKinema deformation model.