UCERF California (UCF)

Authors:

E.H. Field, 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, Y. Zeng

Summary

The Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3) is a model of earthquake occurrence for California developed by the U.S. Geological Survey (USGS) and the Working Group on California Earthquake Probabilities (WGCEP). The time-independent version of UCERF3 (Field et al., 2013; 2014) has been used for the 2014 update of the USGS National Seismic Hazard Maps (Petersen et al., 2014). The model has been translated from its original format into the OpenQuake (OQ) engine by GEM.

Information about the OQ model versions and input files can be found on the Results and Dissemination page.

Interactive Viewer

The viewer below depicts the seismic sources and hazard results in terms of PGA for a return period of 475 years. Click on the menu in the upper right corner to select the layer.

viewer_legend

Tectonic overview

California sits on the western boundary of North America and the eastern boundary of the Pacific Plate, and, farther north, the Juan de Fuca plate. Most of the relative plate motion is accommodated on the dextral San Andreas Fault System, which runs from the Gulf of California in northwestern Mexico east of Los Angeles and northwest through San Jose and San Francisco before terminating at the Mendocino triple junction offshore of northern California. North of Mendocino, the Juan de Fuca plate subducts at the Cascadia subduction zone which runs north to Canada and has paleoseismological evidence for M 9 ruptures. The San Andreas Fault System has notable transpressional and transtensional segments where deformation is more complex and distributed over a network of faults. Notable transpressional regions include the San Bernardino, San Gabriel and Transverse Ranges areas east of Los Angeles (which include threatening thrust faults that underlie many areas of the metropolis) as well as the Santa Cruz mountains between San Jose and Santa Cruz. Transtension is found southeast of Los Angeles from Palm Springs to the Gulf of California, where many normal faults are present and the fault system contains parallel dextral faults such as the San Jacinto and Elsinore faults. East of Los Angeles, transtension extends through the Eastern California Shear Zone and Walker Lane, which contain distributed dextral and normal faults as well as the transverse, sinistral Garlock Fault. This transtensional zone is the western edge of the Basin and Range province which occupies the western North American Cordillera, east to the Wasatch Range of Utah and as far north as southern British Columbia.

Basic Datasets

See Field et al. (2013, 2014) for a description of the datasets used for developing the hazard model.

Hazard Model

Seismic Source Characterisation

The time-independent version of UCERF3 comprises: (1) two alternative fault models, which describe the geometry of the active faults in California; (2) four alternative deformation models, which describe slip-rates on each fault-segment; (3) and various combinations of maximum magnitude, spatial distribution of earthquakes and rate of large-magnitude earthquakes.

Ground Motion Characterisation

Five different ground motion prediction equations (GMPEs) are used, specifically those developed within the Next Generation Attenuation (NGA) West 2 project (Bozorgnia et al., 2014) for active shallow crustal regions. Epistemic uncertainty is further widened by taking into account the potential sample bias in the number of ground motion records within various magnitude and distances ranges (Petersen et al., 2014). The result is that each of the five GMPEs is split into three models, the “mean”, “upper” and “lower” models.

Active Shallow Crust Weight
AbrahamsonEtAl2014NSHMPUpper 0.0407
AbrahamsonEtAl2014 0.1386
AbrahamsonEtAl2014NSHMPLower 0.0407
BooreEtAl2014NSHMPUpper 0.0407
BooreEtAl2014 0.1386
BooreEtAl2014NSHMPLower 0.0407
CampbellBozorgnia2014NSHMPUpper 0.0407
CampbellBozorgnia2014 0.1386
CampbellBozorgnia2014NSHMPLower 0.0407
ChiouYoungs2014NSHMPUpper 0.0407
ChiouYoungs2014 0.1386
ChiouYoungs2014NSHMPLower 0.0407
Idriss2014NSHMPUpper 0.0222
Idriss2014 0.0756
Idriss2014NSHMPLower 0.0222

Results

Hazard curves were computed with the OQ engine for peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2s, 0.5s, 1.0s, and 2s. The computation was performed on a grid of 8661 sites (spaced at approximately 10 km) with reference soil conditions with shear wave velocity in the upper 30 meters (Vs30) of 760-800 m/s.

The hazard map for PGA corresponding to a 10% probability of exceedance in 50 years (475 year return period), can be seen using the interactive viewer. For a more comprehensive set of hazard and risk results, please see the GEM Visualization Tools.

References

Bozorgnia, Y., Abrahamson N., Al Atil, L., Ancheta, T., Atkinson, G., Baker, J., Baltay, A., Boore, D., Campbell, K., Chiou, B., Darragh, R., Day, S., Donahue, J., Graves, R., Gregor, N., Hanks, T., Idriss, I.M., Kamai, R., Kishida, T., Kottke, A., Mahin, S., Rezaeian, S., Rowshandel, B., Seyhan, E., Shahi, S., Shantz, T., Silva, W., Spudich, P., Steward, J., Watson-Lamprey, J., Wooddell, K., Youngs, R., 2014. NGA-West2 research project, Earthquake Spectra 30, 973–987.

Field, E. H., Arrowsmith, R. J., Biasi, G. P., Bird, P., Dawson, T. E., Felzer, K. R., Jackson, D. D., Johnson, K. M., Jordan, T. H., Madden, C., Michael, A. J., Milner, K. R., Page, M. T., Parsons, T., Powers, P. M., Shaw, B. E., Thatcher, W. R., Weldon II, R. J., and Zeng, Y., 2014. Uniform California earthquake rupture forecast, Version 3 (UCERF3) —The time-independent model, Bull. Seismological Soc. Amer. 104, 1122–1180.

Field, E. H., Biasi, G. P., Bird, P., Dawson, T. E., Felzer, K. R., Jackson, D. D., Johnson, K. M., Jordan, T. H., Madden, C., Michael, A. J., Milner, K. R., Page, M. T., Parsons, T., Powers, P. M., Shaw, B. E., Thatcher, W. R., Weldon, R. J., II, and Zeng, Y., 2013. Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)—The Time-Independent Model, U.S.Geological Survey Open-File Report 2013–1165, California Geological Survey Special Report 228, and Southern California Earthquake Center Publication 1792, 97pp., available at http://pubs.usgs.gov/of/2013/1165/.

Petersen, M. D., Moschetti, M. P., Powers, P. M., Mueller, C. S., Haller, K. M., Frankel, A. D., Zeng, Y., Rezaeian, S., Harmsen, S. C., Boyd, O. S., Field, N., Chen, R., Rukstales, K. S., Luco, N., Wheeler, R. L., Williams, R. A., and Olsen, A. H., 2014b. Documentation for the 2014 Update of the United States National Seismic Hazard Maps, U.S. Geological Survey Open-File Report 2014- 1091, 243 pp.