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• 1. [Article] Ground-Rupturing Earthquakes on the Northern Big Bend of the San Andreas Fault, California, 800A.D. to Present

  Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring ...

  Citation × Citation Citation Abstract Copy Title: Ground-Rupturing Earthquakes on the Northern Big Bend of the San Andreas Fault, California, 800A.D. to Present Author: Scharer, Katherine, Weldon, Ray J., II, Biasi, Glenn, Strieg, Ashley, Fumal, Thomas Year: 2017 Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring sites overlap in age and are considered correlative. This study presents the evidence and ages for 11 earthquakes that occurred along the Big Bend section of the southern San Andreas Fault at the Frazier Mountain paleoseismic site. The most recent earthquake to rupture the site was the Mw7.7–7.9 Fort Tejon earthquake of 1857. We use over 30 trench excavations to document the structural and sedimentological evolution of a small pull-apart basin that has been repeatedly faulted and folded by ground-rupturing earthquakes. A sedimentation rate of 0.4 cm/yr and abundant organic material for radiocarbon dating contribute to a record that is considered complete since 800 A.D. and includes 10 paleoearthquakes. Earthquakes have ruptured this location on average every ~100 years over the last 1200 years, but individual intervals range from ~22 to 186 years. The coefficient of variation of the length of time between earthquakes (0.7) indicates quasiperiodic behavior, similar to other sites along the southern San Andreas Fault. Comparison with the earthquake chronology at neighboring sites along the fault indicates that only one other 1857-size earthquake could have occurred since 1350 A.D., and since 800 A.D., the Big Bend and Mojave sections have ruptured together at most 50% of the time in Mw ≥ 7.3 earthquakes. Title: Ground-Rupturing Earthquakes on the Northern Big Bend of the San Andreas Fault, California, 800A.D. to Present Author: Scharer, Katherine, Weldon, Ray J., II, Biasi, Glenn, Strieg, Ashley, Fumal, Thomas Year: 2017 Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring sites overlap in age and are considered correlative. This study presents the evidence and ages for 11 earthquakes that occurred along the Big Bend section of the southern San Andreas Fault at the Frazier Mountain paleoseismic site. The most recent earthquake to rupture the site was the Mw7.7–7.9 Fort Tejon earthquake of 1857. We use over 30 trench excavations to document the structural and sedimentological evolution of a small pull-apart basin that has been repeatedly faulted and folded by ground-rupturing earthquakes. A sedimentation rate of 0.4 cm/yr and abundant organic material for radiocarbon dating contribute to a record that is considered complete since 800 A.D. and includes 10 paleoearthquakes. Earthquakes have ruptured this location on average every ~100 years over the last 1200 years, but individual intervals range from ~22 to 186 years. The coefficient of variation of the length of time between earthquakes (0.7) indicates quasiperiodic behavior, similar to other sites along the southern San Andreas Fault. Comparison with the earthquake chronology at neighboring sites along the fault indicates that only one other 1857-size earthquake could have occurred since 1350 A.D., and since 800 A.D., the Big Bend and Mojave sections have ruptured together at most 50% of the time in Mw ≥ 7.3 earthquakes. Close

• 2. [Article] Appendix C—Deformation Models for UCERF3

  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; ...

  Citation × Citation Citation Abstract Copy Title: Appendix C—Deformation Models for UCERF3 Author: Parsons, Tom, Johnson, Kaj M., Bird, Peter, Bormann, Jayne, Dawson, Timothy E., Field, Edward H., Hammond, William C., Herring, Thomas A., McCaffrey, Robert, Shen, Zheng-kang, Thatcher, Wayne R., Weldon, Ray J., II, Zeng, Yuehua Year: 2013 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. Title: Appendix C—Deformation Models for UCERF3 Author: Parsons, Tom, Johnson, Kaj M., Bird, Peter, Bormann, Jayne, Dawson, Timothy E., Field, Edward H., Hammond, William C., Herring, Thomas A., McCaffrey, Robert, Shen, Zheng-kang, Thatcher, Wayne R., Weldon, Ray J., II, Zeng, Yuehua Year: 2013 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. Close