Integration of Fault Information
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Southern California Earthquake Center University of Southern California, 3651 Trousdale Parkway, Suite 169, Los Angeles, CA 90089-0742 Phone: 213-740-5843 Fax: 213-740-0011 E-Mail: [email protected] Web: www.scec.org Final Technical Report USGS Grant 05HQGR0116 Integration of Fault Information PI: Thomas H. Jordan University of Southern California Southern California Earthquake Center 3651 Trousdale Parkway Los Angeles, CA 90089-0742 213-821-1237; 213-740-0011 (fax) [email protected] Collaborating Scientists Chris Wills, California Geological Survey Ray Weldon, University of Oregon William Bryant, California Geological Survey Period of Performance: April 1, 2005 to March 31, 2007 November 2009 Preface Information about active faults is the starting point for many calculations pertinent to the reduction of earthquake risk. Recognizing its importance, in 2005 the USGS provided support for a joint project between the Southern California Earthquake Center, the California Geological Survey, and the United States Geological Survey to coordinate efforts amongst the three agencies to compile fault information by setting up an active coordination mechanism that will serve all three organizations in the partnership. These efforts are ongoing. With this report, we summarize the fault database work that contributed to the development of Version 2 of the Uniform California Earthquake Rupture Forecast. The authors are Chris Wills, Ray Weldon, and William Bryant. UCERF2 was published in BSSA in August, 2009. The complete reference is E. H. Field, T. E. Dawson, K. R. Felzer, A. D. Frankel, V. Gupta, T. H. Jordan, T. Parsons, M. D. Petersen, R. S. Stein, R. J. Weldon, II, and C. J. Wills, Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2), BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 2009 99: 2053-2107. Table of Contents Introduction ............................................................................................................................ 1 Fault Data .............................................................................................................................. 1 Accuracy of fault parameters ................................................................................................. 5 Updating Fault Section Data.................................................................................................. 5 Changes in fault sections on faults in Northern California ............................................. 6 Southern California fault sections .................................................................................. 7 Alternative Fault Models .............................................................................................. 13 Fault slip rate values............................................................................................................ 15 Alternative Deformation Models................................................................................... 16 Zones of Distributed Shear .................................................................................................. 18 Fault rupture model designations ........................................................................................ 20 Potential Changes to earthquake recurrence models.................................................. 21 Table 1, Fault parameters, including source of trace and slip rate information…….…………23 Main strands of the San Andreas fault system .................................................................... 24 Other significant faults where slip-rate data are available ................................................... 27 Peninsular Ranges ...................................................................................................... 27 Los Angeles Basin and Central Transverse Ranges ................................................... 27 Western Transverse Ranges and Santa Barbara Channel ......................................... 29 Southern Coast Ranges .............................................................................................. 30 San Francisco Bay Area and Central Coast Ranges................................................... 31 Northwestern California ............................................................................................... 33 Northeastern California................................................................................................ 33 Sierra Nevada and western Great Basin ..................................................................... 34 Eastern Transverse Ranges and Mojave Desert......................................................... 36 Zones of distributed shear ................................................................................................... 38 Table 2, Faults being considered for development of deformation models.….………………38 Faults being considered for development of deformation models ....................................... 39 Peninsular Ranges ...................................................................................................... 39 Los Angeles Basin and Central Transverse Ranges ................................................... 39 Western Transverse Ranges and Santa Barbara Channel ......................................... 40 Southern Coast Ranges .............................................................................................. 40 Sierra Nevada and western Great Basin ..................................................................... 40 Eastern Transverse Ranges and Mojave Desert......................................................... 40 Table 3, Alternative deformation models for southern California………...…………..…………41 References ............................................................................................................................. 43 California Fault Parameters for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities, 2007 C.J. Wills1, R.J. Weldon II2, and W. A. Bryant1, 1 California Geological Survey 2 University of Oregon Introduction This report describes development of fault parameters for the 2007 update of the National Seismic Hazard Maps and the Working Group on California Earthquake Probabilities (WGCEP, 2007). These reference parameters are contained within a database intended to be a source of values for use by scientists interested in producing either seismic hazard or deformation models to better understand the current seismic hazards in California. These parameters include descriptions of the geometry and rates of movements of faults throughout the state. These values are intended to provide a starting point for development of more sophisticated deformation models which include known rates of movement on faults as well as geodetic measurements of crustal movement and the rates of movements of the tectonic plates. The values will be used in developing the next generation of the time-independent National Seismic Hazard Maps, and the time-dependant seismic hazard calculations being developed for the WGCEP. Due to the multiple uses of this information, development of these parameters has been coordinated between USGS, CGS and SCEC. SCEC provided the database development and editing tools, in consultation with USGS, Golden. This database has been implemented in Oracle and supports electronic access (e.g., for on-the-fly access). A GUI-based application has also been developed to aid in populating the database. Both the continually updated "living" version of this database, as well as any locked-down official releases (e.g., used in a published model for calculating earthquake probabilities or seismic shaking hazards) are part of the USGS Quaternary Fault and Fold Database. CGS has been primarily responsible for updating and editing of the fault parameters, with extensive input from USGS and SCEC scientists. Fault Data The WGCEP has developed a database of fault parameters, the “California Reference Fault Parameter Database”, to contain that information necessary for development of seismic hazard and deformation models. This database includes information on the geometry and rates of movement of faults in a “Fault Section Database” and information on the timing and amounts of fault displacement in a “PaleoSites Database”. The information in the “Fault Section Database” is discussed in this report. This data set includes the faults included in the National Seismic Hazard Maps (Petersen et al. 1996; Frankel et al. 2002; Cao et al. 2003), updated and modified for the WGCEP. In the “Fault Section Database” currently developed in Oracle by USGS and SCEC, each entry contains the following information: 2 • fault name • fault trace (list of latitudes and longitudes) • average dip estimate • average upper seismogenic depth estimate • average lower seismogenic depth estimate • average long-term slip-rate estimate • average aseismic-slip-factor estimate • average rake estimate This information, except for the lists of latitudes and longitudes that define the geometry, is shown in tabular form in Tables 1 and 2 for each entry in the database. The term "estimate" implies that a formal uncertainty is given. Finally, alternate geometric representations were developed by CFM for some faults; alternate representations are mutually exclusive (meaning if one accurately represents the fault, the other does not). Each fault entry in the database and Tables 1 and 2 is described by the parameters listed above, and is distinguished from adjoining faults by a change in any