Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)

The 2007 Working Group on California Earthquake Probabilities (WGCEP, 2007) presents the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2). This model comprises a time-independent (Poisson-process) earthquake rate model, developed jointly with the National Seismic Hazard Mapping Program and a time-dependent earthquake-probability model, based on recent earthquake rates and stress-renewal statistics conditioned on the date of last event. The models were developed from updated statewide earthquake catalogs and fault deformation databases using a uniform methodology across all regions and implemented in the modular, extensible Open Seismic Hazard Analysis framework. The rate model satisfies integrating measures of deformation across the plate-boundary zone and is consistent with historical seismicity data. An overprediction of earthquake rates found at intermediate magnitudes (6.5≤ M ≤7.0) in previous models has been reduced to within the 95% confidence bounds of the historical earthquake catalog. A logic tree with 480 branches represents the epistemic uncertainties of the full time-dependent model. The mean UCERF 2 time-dependent probability of one or more M ≥6.7 earthquakes in the California region during the next 30 yr is 99.7%; this probability decreases to 46% for M ≥7.5 and to 4.5% for M ≥8.0. These probabilities do not include the Cascadia subduction zone, largely north of California, for which the estimated 30 yr, M ≥8.0 time-dependent probability is 10%. The M ≥6.7 probabilities on major strike-slip faults are consistent with the WGCEP (2003) study in the San Francisco Bay Area and the WGCEP (1995) study in southern California, except for significantly lower estimates along the San Jacinto and Elsinore faults, owing to provisions for larger multisegment ruptures. Important model limitations are discussed.

[1]  C. V. Anderson,et al.  The Federal Emergency Management Agency (FEMA) , 2002 .

[2]  Y. Kagan,et al.  Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, Beta, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in Seven Tectonic Settings , 2004 .

[3]  K. Furlong,et al.  Codependent histories of the San Andreas and San Jacinto fault zones from inversion of fault displacement rates , 2004 .

[4]  J. C. Savage,et al.  An apparent shear zone trending north-northwest across the Mojave Desert into Owens Valley, eastern , 1990 .

[5]  T. Jordan,et al.  OpenSHA: A Developing Community-modeling Environment for Seismic Hazard Analysis , 2003 .

[6]  David D. Jackson,et al.  Seismic hazards in southern California: probable earthquakes, 1994 to 2024 , 1996 .

[7]  D. Wells,et al.  New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement , 1994, Bulletin of the Seismological Society of America.

[8]  S. Ward.  San Francisco Bay Area Earthquake Simulations: A Step Toward a Standard Physical Earthquake Model , 2000 .

[9]  Edward H. Field,et al.  A Summary of Previous Working Groups on California Earthquake Probabilities , 2007 .

[10]  S. Wiemer,et al.  Earthquake Likelihood Model Testing , 2007 .

[11]  Edward H. Field,et al.  Overview of the Working Group for the Development of Regional Earthquake Likelihood Models (RELM) , 2005 .

[12]  Y. Kagan,et al.  Worldwide Doublets of Large Shallow Earthquakes , 1999 .

[13]  Steven G. Wesnousky,et al.  Predicting the endpoints of earthquake ruptures , 2006, Nature.

[14]  Timothy E. Dawson,et al.  Development of Final A-Fault Rupture Models for WGCEP/ NSHMP Earthquake Rate Model 2 , 2008 .

[15]  A. Michael,et al.  Subsurface Structure and Kinematics of the Calaveras–Hayward Fault Stepover from Three-Dimensional Vp and Seismicity, San Francisco Bay Region, California , 2005 .

[16]  C. Wills,et al.  Overview of the southern San Andreas fault model , 2008 .

[17]  Takashi Nakata,et al.  Time‐predictable recurrence model for large earthquakes , 1980 .

[18]  Y. Y.,et al.  Random stress and earthquake statistics : time dependence , 2008 .

[19]  I. B. Everingham.  Large earthquakes in the New Guinea-Solomon Islands area, 1873 1972 , 1974 .

[20]  W. Bakun.  Seismicity of California's north coast , 2000 .

[21]  Vipin Gupta,et al.  Appendix N: Conditional, Time- Dependent Probabilities for Segmented Type-A Faults in the WGCEP UCERF 2 , 2008 .

[22]  Brendan J. Meade,et al.  Block models of crustal motion in southern California constrained by GPS measurements , 2005 .

[23]  B. Gutenberg,et al.  Frequency of Earthquakes in California , 1944, Nature.

[24]  Paul G. Richards,et al.  Quantitative Seismology: Theory and Methods , 1980 .

[25]  Mark D. Petersen,et al.  Simulations of Seismic Hazard for the Pacific Northwest of the United States from Earthquakes Associated with the Cascadia Subduction Zone , 2002 .

[26]  Mark D. Petersen,et al.  Cascadia Subduction Zone , 2008 .

[27]  Kelin Wang,et al.  Three‐dimensional dislocation model for great earthquakes of the Cascadia Subduction Zone , 1997 .

[28]  W. Ellsworth,et al.  Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake , 1993, Science.

[29]  Charles L. Lawson,et al.  Solving least squares problems , 1976, Classics in applied mathematics.

[30]  R. Simpson,et al.  Spatial and Temporal Deformation along the Northern San Jacinto Fault, Southern California: Implications for Slip Rates , 2002 .

[31]  Tom Parsons,et al.  Significance of stress transfer in time‐dependent earthquake probability calculations , 2004 .

[32]  R. Weldon,et al.  Deformation across the western United States: A local estimate of Pacific‐North America transform deformation , 1994 .

[33]  Nitin Gupta,et al.  Hazard Calculations for the WGCEP-2002 Earthquake Forecast Using OpenSHA and Distributed Object Technologies , 2005 .

[34]  P. Reasenberg,et al.  Observing Earthquakes Triggered in the Near Field by Dynamic Deformations , 2003 .

[35]  Kristy F. Tiampo,et al.  Virtual California: Fault Model, Frictional Parameters, Applications , 2006 .

[36]  David D. Jackson,et al.  A mutually consistent seismic-hazard source model for southern California , 1999 .

[37]  P. A. McCrory,et al.  Depth to the Juan De Fuca slab beneath the Cascadia subduction margin - a 3-D model for sorting earthquakes , 2004 .

[38]  Jeanne L. Hardebeck.  Stress triggering and earthquake probability estimates , 2004 .

[39]  C. Cornell.  Engineering seismic risk analysis , 1968 .

[40]  Tom Parsons.  Monte Carlo method for determining earthquake recurrence parameters from short paleoseismic catalogs: Example calculations for California , 2008 .

[41]  Timothy E. Dawson,et al.  The 2002 Denali Fault Earthquake, Alaska: A Large Magnitude, Slip-Partitioned Event , 2003, Science.

[42]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[43]  A. Frankel,et al.  Spatial Seismicity Rates and Maximum Magnitudes for Background Earthquakes , 2008 .

[44]  Dylan Blumentritt,et al.  Slip rate of the Calico fault: Implications for geologic versus geodetic rate discrepancy in the Eastern California Shear Zone , 2007 .

[45]  K. Kelson,et al.  Timing of Late Holocene Paleoearthquakes on the Northern San Andreas Fault at the Fort Ross Orchard Site, Sonoma County, California , 2006 .

[46]  David D. Jackson.  The Case for Huge Earthquakes , 1996 .

[47]  Glenn P. Biasi,et al.  Past and Future Earthquakes on the San Andreas Fault , 2005, Science.

[48]  Susan E. Hough.  The Case Against Huge Earthquakes , 1996 .

[49]  Yukio Hagiwara,et al.  Probability of earthquake occurrence as obtained from a Weibull distribution analysis of crustal strain , 1974 .

[50]  D. P. Schwartz,et al.  Fault behavior and characteristic earthquakes: Examples from the Wasatch and San Andreas Fault Zones , 1984 .

[51]  William A. Bryant,et al.  Probabilistic seismic hazard assessment for the state of California , 1996 .

[52]  Thomas C. Hanks,et al.  M-logA Observations for Recent Large Earthquakes , 2008 .

[53]  H. Kanamori,et al.  A moment magnitude scale , 1979 .

[54]  Yan Y. Kagan,et al.  Random stress and earthquake statistics: spatial dependence , 1987 .

[55]  Christopher T. Russell,et al.  Growing “Alfvenic” modes in the upstream region of Saturn , 1994 .

[56]  Gregory C. Beroza,et al.  Living on an Active Earth: Perspectives on Earthquake Science , 2003 .

[57]  C. Goldfinger,et al.  Rupture lengths and temporal history of significant earthquakes on the offshore and north coast segments of the Northern San Andreas Fault based on turbidite stratigraphy , 2007 .

[58]  Matthew C. Gerstenberger,et al.  Real-time forecasts of tomorrow's earthquakes in California , 2005, Nature.

[59]  T. Parsons.  Post-1906 stress recovery of the San Andreas fault system calculated from three-dimensional finite element analysis , 2002 .

[60]  M Magee,et al.  The Cape Mendocino, California, Earthquakes of April 1992: Subduction at the Triple Junction , 1993, Science.

[61]  Richard N. Hey,et al.  Pole of rotation analysis of present-day Juan de Fuca Plate motion , 1984 .

[62]  T. Rikitake.  Probability of earthquake occurrence as estimated from crustal strain , 1974 .

[63]  P. Bodin,et al.  Triggering of earthquake aftershocks by dynamic stresses , 2000, Nature.

[64]  Kenji Satake,et al.  Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions , 2003 .

[65]  W. Menke.  Geophysical data analysis : discrete inverse theory , 1984 .

[66]  K. Sieh,et al.  Long-term slip rate of the southern San Andreas Fault from 10Be-26Al surface exposure dating of an offset alluvial fan , 2006 .

[67]  G. Biasi,et al.  Estimating Surface Rupture Length and Magnitude of Paleoearthquakes from Point Measurements of Rupture Displacement , 2006 .

[68]  Jerome A. Treiman,et al.  Community Fault Model (CFM) for Southern California , 2007 .

[69]  Yehuda Bock,et al.  Diffuse interseismic deformation across the Pacific–North America plate boundary , 2007 .

[70]  Brian F. Atwater,et al.  Recurrence Intervals for Great Earthquakes of the Past 3,500 Years at Northeastern Willapa Bay, Washington , 1997 .

[71]  Mark D. Petersen,et al.  United States National Seismic Hazard Maps , 2008 .

[72]  D. P. Schwartz,et al.  Probabilities of Large Earthquakes in the San Francisco Bay Region, California , 1990 .

[73]  B. Meade,et al.  Spatial localization of moment deficits in southern California , 2004 .

[74]  E. Humphreys,et al.  Fault slip rates, effects of elastic heterogeneity on geodetic data, and the strength of the lower crust in the Salton Trough region, southern California , 2005 .

[75]  Robert R. Youngs.  Living on an Active Earth: Perspectives on Earthquake Science , 2005 .

[76]  D. Perkins,et al.  National Seismic-Hazard Maps: Documentation June 1996 , 1996 .

[77]  Thomas C. Hanks,et al.  An Empirical Model for Earthquake Probabilities in the San Francisco Bay Region, California, 2002-2031 , 2003 .

[78]  Tousson Toppozada,et al.  San Andreas Fault Zone, California: M ≥5.5 Earthquake History , 2002 .

[79]  Steven M. Day,et al.  Dynamics of fault interaction: parallel strike‐slip faults , 1993 .

[80]  William L. Ellsworth,et al.  A Brownian Model for Recurrent Earthquakes , 2002 .

[81]  Wayne Thatcher,et al.  Resolution of fault slip along the 470‐km‐long rupture of the great 1906 San Francisco earthquake and its implications , 1997 .

[82]  Timothy E. Dawson,et al.  Summary of geologic data and development of A-Priori rupture models for the Elsinore, San Jacinto and Garlock faults , 2008 .

[83]  P. Bird.  An updated digital model of plate boundaries , 2003 .

[84]  L. Knopoff,et al.  Is the sequence of earthquakes in Southern California, with aftershocks removed, Poissonian? , 1974, Bulletin of the Seismological Society of America.

[85]  Maurice S. Power,et al.  An Overview of the NGA Project , 2008 .

[86]  E. Field,et al.  A-Priori Rupture Models for Northern California Type-A Faults , 2008 .

[87]  Yuri Fialko,et al.  Interseismic strain accumulation and the earthquake potential on the southern San Andreas fault system , 2006, Nature.

[88]  E. Hauksson,et al.  The Seismogenic Thickness of the Southern California Crust , 2004 .

[89]  Thomas C. Hanks,et al.  A Bilinear Source-Scaling Model for M-log A Observations of Continental Earthquakes , 2002 .

[90]  Richard A. Schweickert,et al.  60 k.y. record of extension across the western boundary of the Basin and Range province: Estimate of slip rates from offset shoreline terraces and a catastrophic slide beneath Lake Tahoe , 2006 .

[91]  Ray J. Weldon,et al.  California Fault Parameters for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities 2007 , 2008 .

[92]  Robert J. Budnitz,et al.  Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts , 1997 .

[93]  F. Cotton,et al.  Redistribution of dynamic stress during coseismic ruptures: Evidence for fault interaction and earthquake triggering , 1999 .

[94]  Charles S. Mueller,et al.  Documentation for the 2008 update of the United States National Seismic Hazard Maps , 2008 .

[95]  Ray J. Weldon,et al.  Estimating prehistoric earthquake magnitude from point measurements of surface rupture , 1999, Bulletin of the Seismological Society of America.

[96]  S. T. Algermissen,et al.  A probabilistic estimate of maximum acceleration in rock in the contiguous United States , 1976 .

[97]  Earthquake Rate Model 2.2 of the 2007 Working Group for California Earthquake Probabilities, Appendix D: Magnitude-Area Relationships , 2007 .

[98]  K. Hudnut,et al.  Fault Interactions and Large Complex Earthquakes in the Los Angeles Area , 2003, Science.

[99]  K. Felzer.  Calculating California seismicity rates , 2008 .

[100]  T. Hanks,et al.  M ≧ 6 earthquakes in southern California during the twentieth century: No evidence for a seismicity or moment deficit , 1998, Bulletin of the Seismological Society of America.

[101]  Glenn P. Biasi,et al.  Wrightwood and the earthquake cycle: What a long recurrence record tells us about how faults work , 2004 .

[102]  Mark D. Petersen,et al.  Time-independent and Time-dependent Seismic Hazard Assessment for the State of California: Uniform California Earthquake Rupture Forecast Model 1.0 , 2007 .

[103]  H. F. Reid.  The elastic-rebound theory of earthquakes , 1911 .

[104]  Kerry E Sieh,et al.  Complexities of the San Andreas fault near San Gorgonio Pass: Implications for large earthquakes , 2003 .

[105]  S. Harmsen,et al.  Documentation for the 2002 update of the national seismic hazard maps , 2002 .

[106]  K. Felzer,et al.  WGCEP historical California earthquake catalog , 2008 .

[107]  S. Wesnousky,et al.  Do historical rates of seismicity in southern California require the occurrence of earthquake magnitudes greater than would be predicted from fault length? , 1997, Bulletin of the Seismological Society of America.

[108]  James H. Dieterich,et al.  Probabilities of large earthquakes occurring in California on the San Andreas Fault , 1988 .

[109]  S. P. Nishenko,et al.  A generic recurrence interval distribution for earthquake forecasting , 1987 .

[110]  Morgan T. Page,et al.  Methodologies for Earthquake Hazard Assessment: Model Uncertainty and the WGCEP-2002 Forecast , 2006 .

[111]  Max A. Meju,et al.  Geophysical data analysis , 1994 .

[112]  R. J. Ii Weldon,et al.  Compilation of surface creep on California faults and comparison of WGCEP 2007 deformation model to Pacific-North American plate Mmtion , 2008 .

[113]  K. Sieh,et al.  Behavior of the southernmost San Andreas Fault during the past 300 years , 1990 .