2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Sevier/Toroweap fault zone (northern)	Utah

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)	87

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.33
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.56	23.3	3.09e-04	1.710	0.2
50	0.47	19.6	2.18e-04	1.558	0.6
60	0.42	17.3	1.70e-04	1.451	0.2

Comments
The assigned preferred vertical slip rate for the northern Sevier/Toroweap fault is based on measured offset of 200 m (Anderson and others, 1978) of 560 ka Red Canyon volcanic flow (Best and others, 1980). There are no other studies to base assigning a minimum and maximum slip rate to this part of the fault. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Anderson, R.E., Bucknam, R.C., and Hamblin, W.K., 1978, Road log to the Quaternary tectonics of the Intermountain seismic belt between Provo and Cedar City, Utah: Geological Society of America, Rocky Mountain Section Annual Meeting, Provo, Utah, Field Trip no. 8, 50 p. Best, M.G., McKee, E.H., and Damon, P.E., 1980, Space-time-composition patterns of late Cenozoic mafic volcanism, southwestern Utah and adjoining areas: American Journal of Science, v. 280, p. 1035–1050. 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

Anderson, R.E., Bucknam, R.C., and Hamblin, W.K., 1978, Road log to the Quaternary tectonics of the Intermountain seismic belt between Provo and Cedar City, Utah: Geological Society of America, Rocky Mountain Section Annual Meeting, Provo, Utah, Field Trip no. 8, 50 p.
Best, M.G., McKee, E.H., and Damon, P.E., 1980, Space-time-composition patterns of late Cenozoic mafic volcanism, southwestern Utah and adjoining areas: American Journal of Science, v. 280, p. 1035–1050.
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.