United States of America (USA)

Author:

M.D. Petersen, M.P. Moschetti, P.M. Powers, C.S. Mueller, K. M. Haller, A.D. Frankel, Y. Zeng, S. Rezaeian, S.C. Harmsen, O.S. Boyd, E.H. Field, R. Chen, K.S. Rukstales, N. Luco, R.L. Wheeler, R.A. Williams, A.H. Olsen

Summary

The 2014 United States National Seismic Hazard Model (Petersen et al., 2014), covers the conterminous United States and was developed by the United States Geological Survey (USGS) within the National Seismic Hazard Model Project (NSHMP). The model has been translated from its original format into the OpenQuake (OQ) engine by GEM. The California portion of the the model is based on the Uniform California Earthquake Rupture Forecast version 3 (UCERF3, see UCF).

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

The contiguous US occupies central North America; tectonic activity is primarily found in the western plate margins, most clearly defined as the San Andreas Fault System in California (the boundary between the North American and Pacific plates) and the Cascadia subduction zone (where the Juan de Fuca plate subducts beneath North America) in northern California north to southern British Columbia. These plate boundaries lead to distributed deformation within the North American crust as well. Subduction at the Cascadia trench is oblique, leading to the northward translation of the forearc (western Oregon and Washington), which is linked to shortening at the northern end of the forearc where it impinges into more stable British Columbia; this is expressed as faulting in the Puget Sound region of Washington State. Some fraction (roughly 1/4 to 1/3) of Pacific-North American relative motion is accommodated within North America rather than on the San Andreas Fault. This fraction is distributed through many strike-slip and normal faults within the Basin and Range and Eastern California Shear Zone provinces of eastern California through Utah. The Basin and Range province as well as the Rocky Mountains also have many normal fault systems with very low slip rates that may still produce M 7+ earthquakes such as the Hebgen Lake and Borah Peak earthquakes. Though strain rates are negligible, old faults in the central and eastern US are episodically reactivated, and have historically produced damaging earthquakes such as the New Madrid and Charleston earthquakes sequences in early US history. Because of the cold cratonic crust and low attenuation, ground shaking from these earthquakes may be much higher than in the more active American West.

Basic Datasets

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

Hazard Model

Seismic Source Characterisation

The seismic source characterisation incorporates: (1) smoothed seismicity models; (2) background source zones in areas without recent earthquake activity and (3) fault sources that characterize earthquakes on active faults. Details of the earthquake source models can be found in Moschetti et al. (2015) and Frankel et al. (2015)

Ground Motion Characterisation

The model applies ground motion prediction equations (GMPEs) for stable continental regions, shallow crustal earthquakes, subduction interface earthquakes, and deep intraslab earthquakes. The GMPEs are discussed in more detail in Rezaeian et al. (2015).

Active Shallow Crust Weight
AbrahamsonEtAl2014NSHMPMean 0.22
BooreEtAl2014NSHMPMean 0.22
CampbellBozorgnia2014NSHMPMean 0.22
ChiouYoungs2014NSHMPMean 0.22
Idriss2014NSHMPMean 0.12
Subduction Inslab Weight
AbrahamsonEtAl2015SSlab 0.333
ZhaoEtAl2006SSlabNSHMP2014 0.334
AtkinsonBoore2003SSlabNSHMP2008 0.1665
AtkinsonBoore2003SSlabCascadiaNSHMP2008 0.1665
Subduction Interface Weight
AbrahamsonEtAl2015SInter 0.3
AtkinsonMacias2009 0.3
ZhaoEtAl2006SInter 0.3
AtkinsonBoore2003SInterNSHMP2008 0.1
Stable Shallow Faults Weight
FrankelEtAl1996MwNSHMP2008 0.06
ToroEtAl2002SHARE 0.11
SilvaEtAl2002MwNSHMP2008 0.06
Campbell2003MwNSHMP2008 0.11
TavakoliPezeshk2005MwNSHMP2008 0.11
AtkinsonBoore2006Modified2011 0.22
PezeshkEtAl2011NEHRPBC 0.15
SomervilleEtAl2001NSHMP2008 0.1
BooreAtkinson2011 0.08
Stable Shallow Gridded Weight
FrankelEtAl1996MwNSHMP2008 0.06
ToroEtAl2002SHARE 0.13
SilvaEtAl2002MwNSHMP2008 0.06
Campbell2003MwNSHMP2008 0.13
TavakoliPezeshk2005MwNSHMP2008 0.13
AtkinsonBoore2006Modified2011 0.25
PezeshkEtAl2011NEHRPBC 0.16
Atkinson2008prime 0.08

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 94480 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

Frankel, A. D., Chen, R., Petersen, M., Moschetti, M., and Sherrod, B., 2015. 2014 Update of the Pacific Northwest portion of the U.S. National Seismic Hazard Maps, Earthquake Spectra 31, S131–S148.

Moschetti, M. P., Powers, P. M., Boyd, O., Chen, R., Field, E., Frankel, A. D., Haller, K., Harmsen, S., Mueller, C., Wheeler, R., and Petersen, M. D., 2015. Seismic source characterization for the 2014 update of the U.S. national seismic hazard model, Earthquake Spectra 31,

Petersen, M.D., Frankel, A.D., Harmsen, S.C., Mueller, C.S., Haller, K.M., Wheeler, R.L., Wesson, R.L., Zeng, Y., Boyd, O.S., Perkins, D.M., Luco, N., Field, E.H., Wills, C.J., Rukstales, K.S., 2008. Documentation for the 2008 Update of the United States National Seismic Hazard Maps (USGS Open File Report No. OFR 2008-1128). U.S. Geological Survey, Reston, Virginia.

Petersen, M.D., Moschetti, M.P., Powers, P.M., Mueller, C.S., Haller, K.M., Frankel, A.D., Zeng, Yuehua, Rezaeian, Sanaz, Harmsen, S.C., Boyd, O.S., Field, Ned, Chen, Rui, Rukstales, K.S., Luco, Nico, Wheeler, R.L., Williams, R.A., and Olsen, A.H., 2014, Documentation for the 2014 update of the United States national seismic hazard maps: U.S. Geological Survey Open-File Report 2014–1091, 243 p.

Rezaeian, S., Petersen, M. D., Moschetti, M. P., Powers, P., Harmsen, S. C., and Frankel, A. D., 2014. Implementation of NGA-West2 Ground Motion Models in the 2014 U.S. National Seismic Hazard Maps, Earthquake Spectra 30, 1319–1333.