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.

Appendixes

• Appendix A (PDF, 1 MB), Updates to the California Reference Fault Parameter Database—Uniform California Earthquake Rupture Forecast, Version 3 Fault Models 3.1 and 3.2, By Timothy E. Dawson
• Appendix B (PDF, 1.8 MB), Geologic-Slip-Rate Data and Geologic Deformation Model, By Timothy E. Dawson, and Ray J. Weldon, II
  • Table B1 (XLSX, 185 KB)
• Appendix C (PDF, 9.8 MB), Deformation Models for UCERF3, By Tom Parsons, Kaj M. Johnson, Peter Bird, Jayne Bormann, Timothy E. Dawson, Edward H. Field, William C. Hammond, Thomas A. Herring, Rob McCaffrey, Zhen-Kang Shen, Wayne R. Thatcher, Ray J. Weldon, II, and Yuehua Zeng
• Appendix D (PDF, 2.4 MB), Compilation of Creep Rate Data for California Faults and Calculation of Moment Reduction Due to Creep, By Ray J. Weldon, II, David A. Schmidt, Lauren J. Austin, Elise M. Weldon, and Timothy E. Dawson
• Appendix E (PDF, 1.8 MB), Evaluation of Magnitude-Scaling Relationships and Depth of Rupture, By Bruce E. Shaw
• Appendix F (PDF, 2.1 MB), Distribution of Slip in Ruptures, By Glenn P. Biasi, Ray J. Weldon, II, Timothy E. Dawson
• Appendix G (PDF, 1 MB), Paleoseismic Sites Recurrence Database, By Ray J. Weldon, II, Timothy E. Dawson, Glenn Biasi, Christopher Madden, and Ashley R. Streig
• Appendix H (PDF, 1.6 MB), Maximum Likelihood Recurrence Intervals for California Paleoseismic Sites, By Glenn P. Biasi
• Appendix I (PDF, 4.1 MB), Probability of Detection of Ground Rupture at Paleoseismic Sites, By Ray J. Weldon, II and Glenn P. Biasi
• Appendix J (PDF, 1.2 MB), Fault-to-Fault Rupture Probabilities, By Glenn P. Biasi, Tom Parsons, Ray J. Weldon, II, and Timothy E. Dawson
• Appendix K (PDF, 210 KB), The UCERF3 Earthquake Catalog, By K.R. Felzer
  • Earthquake Catalog (TXT, 5.4 MB)
• Appendix L (PDF, 580 KB), Estimate of the Seismicity Rate and Magnitude-Frequency Distribution of Earthquakes in California from 1850 to 2011, By K.R. Felzer
• Appendix M (PDF, 3.9 MB), Adaptive Smoothed Seismicity Model, By K.R. Felzer
  • Supplemental Materials (ZIP, 110 KB)
• Appendix N (PDF, 6 MB), Grand Inversion Implementation and Testing, By Morgan T. Page, Edward H. Field, Kevin R. Milner, and Peter M. Powers
  • Supplemental Material
• Appendix O (PDF, 1 MB), Gridded Seismicity Sources, By Peter M. Powers and Edward H. Field
• Appendix P (PDF, 41 MB), Models of Earthquake Recurrence and Down-Dip Edge of Rupture for the Cascadia Subduction Zone, By Arthur D. Frankel, and Mark D. Petersen
• Appendix Q (PDF, 2.4 MB), The Empirical Model, By K.R. Felzer
  • Earthquake Catalog (TXT, 5.4 MB)
• Appendix R (PDF, 4.4 MB), Compilation of Slip-in-the-Last-Event Data and Analysis of Last Event, Repeated Slip, and Average Displacement for Recent and Prehistoric Ruptures, By Chris Madden, David E. Haddad, J. Barrett Salisbury, Olaf Zielke, J. Ramón Arrowsmith, Ray J.Weldon, II, and Javier Colunga
  • Supplemental materials (ZIP, 42.6 MB)
• Appendix S (PDF, 7.8 MB), Constraining Epidemic Type Aftershock Sequence (ETAS) Parameters from the Uniform California Earthquake Rupture Forecast, Version 3 Catalog and Validating the ETAS Model for Magnitude 6.5 or Greater Earthquakes, By Jeanne L. Hardebeck
• Appendix T (PDF, 5.4 MB), Defining the Inversion Rupture Set Using Plausibility Filters, By Kevin R. Milner, Morgan T. Page, Edward H. Field, Tom Parsons, Glenn P. Biasi, and Bruce E. Shaw

First posted November 5, 2013