2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Cottonwood Mountain fault	Oregon

GEOMETRY
Dip (degrees)	50/60/40
Dip direction	NE
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	42

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	6.97
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.14	23.3	1.30e-04	1.243	0.2
50	0.12	19.6	9.16e-05	1.091	0.6
60	0.10	17.3	7.17e-05	0.984	0.2

Comments
The assigned slip rate is based on numerous fault scarp profiles and estimated ages of late Quaternary deposits to determine long-term slip rates of 0.03-0.15 mm/yr (Knudsen and others, 1994). Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Knudsen, K.L., 1994, The Cottonwood Mountain fault—Holocene and Pleistocene fault activity in east-central Oregon: Geological Society of America Abstracts with Programs, v. 26, no. 7, p. 191. 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

Knudsen, K.L., 1994, The Cottonwood Mountain fault—Holocene and Pleistocene fault activity in east-central Oregon: Geological Society of America Abstracts with Programs, v. 26, no. 7, p. 191.
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.