2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Lost River fault	Idaho

GEOMETRY
Dip (degrees)	40/60/45
Dip direction	SW
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	141

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.00
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	a-value	Branch Weight
40	0.23	23.3	2.073	0.2
45	0.21	21.2	1.891	0.6
60	0.17	17.3	1.763	0.2

Comments
The preferred vertical slip rate is the average of published slip rates from two of the central sections of the fault. Specifically, trenching on the Thousand Springs section showed that 2.1 m of vertical offset in 1983 released strain that had been accumulating since 10-11 ka, for a slip rate of 0.21 mm/yr (Vincent, 1995). Trenching on the Pass Creek section showed 13.1-18.1 m of vertical offset of a 140- to 220-ka surface, for a slip rate of 0.06-0.13 mm/yr (Olig and others, 1995); their preferred rate is 0.095 mm/yr. Assigned characteristic magnitude based on Borah Peak earthquake. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Comments

The preferred vertical slip rate is the average of published slip rates from two of the central sections of the fault. Specifically, trenching on the Thousand Springs section showed that 2.1 m of vertical offset in 1983 released strain that had been accumulating since 10-11 ka, for a slip rate of 0.21 mm/yr (Vincent, 1995). Trenching on the Pass Creek section showed 13.1-18.1 m of vertical offset of a 140- to 220-ka surface, for a slip rate of 0.06-0.13 mm/yr (Olig and others, 1995); their preferred rate is 0.095 mm/yr. Assigned characteristic magnitude based on Borah Peak earthquake. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Olig, S.S., Gorton, A.E., Bott, J.D., Wong, I.G., Knuepfer, P.L.K., Forman, S.L., Smith, R.P., and Simpson, D., 1995, Paleoseismic investigation of the southern Lost River fault zone, Idaho: Technical report to Lockheed Idaho Technologies Company, Idaho National Engineering Laboratory, Idaho Falls, Idaho, under Contract C93-134020, June 1995, 81 p., 5 pls. Crone, A.J., Machette, M.N., Bonilla, M.G., Lienkaemper, J.J., Pierce, K.L., Scott, W.E., and Bucknam, R.C., 1985, Characteristics of surface faulting accompanying the Borah Peak earthquake, central Idaho, in Stein, R.S., and Bucknam, R.C., eds., Proceedings of workshop XXVIII on the Borah Peak, Idaho, earthquake: U.S. Geological Survey Open-File Report 85-290, v. A, p. 43-58. Crone, A.J., Machette, M.N., Bonilla, M.G., Lienkaemper, J.J., Pierce, K.L., Scott, W.E., and Bucknam, R.C., 1987, Surface faulting accompanying the Borah Peak earthquake and segmentation of the Lost River fault, central Idaho: Bulletin of the Seismological Society of America, v. 77, p. 739-770. Scott, W.E., 1982, Surficial geologic map of the eastern Snake River Plain and adjacent areas, 111° to 115° W., Idaho and Wyoming: U.S. Geological Survey Miscellaneous Investigations Series Map I-1372, 2 sheets, scale 1:250,000. 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. Vincent, K.R., 1995, Implications for models of fault behavior from earthquake surface-displacement along adjacent segments of the Lost River fault, Idaho: Tucson, University of Arizona, unpublished Ph.D. dissertation, 152 p.

Selected References

Olig, S.S., Gorton, A.E., Bott, J.D., Wong, I.G., Knuepfer, P.L.K., Forman, S.L., Smith, R.P., and Simpson, D., 1995, Paleoseismic investigation of the southern Lost River fault zone, Idaho: Technical report to Lockheed Idaho Technologies Company, Idaho National Engineering Laboratory, Idaho Falls, Idaho, under Contract C93-134020, June 1995, 81 p., 5 pls.
Crone, A.J., Machette, M.N., Bonilla, M.G., Lienkaemper, J.J., Pierce, K.L., Scott, W.E., and Bucknam, R.C., 1985, Characteristics of surface faulting accompanying the Borah Peak earthquake, central Idaho, in Stein, R.S., and Bucknam, R.C., eds., Proceedings of workshop XXVIII on the Borah Peak, Idaho, earthquake: U.S. Geological Survey Open-File Report 85-290, v. A, p. 43-58.
Crone, A.J., Machette, M.N., Bonilla, M.G., Lienkaemper, J.J., Pierce, K.L., Scott, W.E., and Bucknam, R.C., 1987, Surface faulting accompanying the Borah Peak earthquake and segmentation of the Lost River fault, central Idaho: Bulletin of the Seismological Society of America, v. 77, p. 739-770.
Scott, W.E., 1982, Surficial geologic map of the eastern Snake River Plain and adjacent areas, 111° to 115° W., Idaho and Wyoming: U.S. Geological Survey Miscellaneous Investigations Series Map I-1372, 2 sheets, scale 1:250,000.
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.
Vincent, K.R., 1995, Implications for models of fault behavior from earthquake surface-displacement along adjacent segments of the Lost River fault, Idaho: Tucson, University of Arizona, unpublished Ph.D. dissertation, 152 p.