2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Blacktail fault	Montana

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

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	6.94
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.05	23.3	4.51e-05	0.749	0.2
50	0.04	19.6	3.17e-05	0.597	0.6
60	0.04	17.3	2.48e-05	0.490	0.2

Comments
The preferred vertical slip rate is based on data presented by Stickney and Bartholomew (1987) and Bartholomew and others (1999) that suggest there is 4-5 m of offset of inferred upper (<150 ka) Quaternary deposits. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Bartholomew, M.J., Stickney, M.C., and Wasklewicz, T.A., 2004, Interaction between the northern Basin and Range and the Yellowstone stress fields near the Red Rock fault, southwestern Montana: Geological Society of America Abstracts with Programs, v. 36, no. 4, p. 12. 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. Stickney, M.C., and Bartholomew, M.J., 1987, Seismicity and late Quaternary faulting of the northern Basin and Range province, Montana and Idaho: Bulletin of the Seismological Society of America, v. 77, p. 1602-1625.

Selected References

Bartholomew, M.J., Stickney, M.C., and Wasklewicz, T.A., 2004, Interaction between the northern Basin and Range and the Yellowstone stress fields near the Red Rock fault, southwestern Montana: Geological Society of America Abstracts with Programs, v. 36, no. 4, p. 12.
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.
Stickney, M.C., and Bartholomew, M.J., 1987, Seismicity and late Quaternary faulting of the northern Basin and Range province, Montana and Idaho: Bulletin of the Seismological Society of America, v. 77, p. 1602-1625.