2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Santa Rosa fault system	Oregon

GEOMETRY
Dip (degrees)	50/40/60
Dip direction	W
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	171

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.50
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.20	23.3		1.485	0.2
50	0.17	19.6	5.39e-05	1.333	0.6
60	0.15	17.3		1.226	0.2

Comments
The assigned vertical slip rate is based on the reported minimum rate of 0.01-0.13 mm/yr reflecting the most recent interval of faulting (Narwold, 1999; 2001). These slip rates are based on field measurements of surface offset at several locations along the northern Santa Rosa Range fault system and estimated ages for the faulted deposits based on calcic soil development. The characteristic magnitude for this fault is fixed at M7.5 even though the length of the fault would permit a larger earthquake. We assigned the upper limit of the range of minimum rates. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Comments

The assigned vertical slip rate is based on the reported minimum rate of 0.01-0.13 mm/yr reflecting the most recent interval of faulting (Narwold, 1999; 2001). These slip rates are based on field measurements of surface offset at several locations along the northern Santa Rosa Range fault system and estimated ages for the faulted deposits based on calcic soil development. The characteristic magnitude for this fault is fixed at M7.5 even though the length of the fault would permit a larger earthquake. We assigned the upper limit of the range of minimum rates. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Narwold, C.F., 2001, Late Quaternary soils and faulting along the Quinn River fault zone, northern Nevada, southeastern Oregon: Arcata, California, Humboldt State University, unpublished M.S. thesis, 76 p., 4, scale 1:48,000. Narwold, C.F., 1999, Late Quaternary faulting along the Quinn River fault zone—A soils investigation, in Quaternary geology of the northern Quinn River and Alvord Valleys, southeastern Oregon: Friends of the Pleistocene field trip guide, September 24-26, 1999, Appendix 1, p. 1–18. Lund, W.R., ed., 2006, Basin and Range Province Earthquake Working Group seismic-hazard recommendations to the U.S. Geological Survey National Seismic Hazard Mapping Program: Utah Geological Survey Open-File Report 477, 23 p, ugspub.nr.utah.gov/publications/open_file_reports/OFR-477.pdf.

Selected References

Narwold, C.F., 2001, Late Quaternary soils and faulting along the Quinn River fault zone, northern Nevada, southeastern Oregon: Arcata, California, Humboldt State University, unpublished M.S. thesis, 76 p., 4, scale 1:48,000.
Narwold, C.F., 1999, Late Quaternary faulting along the Quinn River fault zone—A soils investigation, in Quaternary geology of the northern Quinn River and Alvord Valleys, southeastern Oregon: Friends of the Pleistocene field trip guide, September 24-26, 1999, Appendix 1, p. 1–18.
Lund, W.R., ed., 2006, Basin and Range Province Earthquake Working Group seismic-hazard recommendations to the U.S. Geological Survey National Seismic Hazard Mapping Program: Utah Geological Survey Open-File Report 477, 23 p, ugspub.nr.utah.gov/publications/open_file_reports/OFR-477.pdf.