2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
East Franklin Mountains fault	Texas

GEOMETRY
Dip (degrees)	50/40/60
Dip direction	E
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	48

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.03
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.16	23.3	1.33e-04	1.144	0.2
50	0.13	19.6	9.40e-05	0.992	0.6
60	0.12	17.3	7.35e-05	0.885	0.2

Comments
The preferred vertical slip rate is based on three of the twenty-one scarp profiles (Machette, 1987). Two profiles gave 30.3 and 34.8 m heights for offsets of the Jornada I surface, which Machette estimated to be 350 +/- 50 ka. From these data he calculated minimum slip rates of 0.08-0.1 mm/yr since 350 ka. A third profile yielded a 59.6 m height for an offset of the Camp Rice Formation, which he estimated to be approximately 500 ka, for a slip rate of 0.12 mm/yr since 500 ka. The only trench across the fault revealed evidence of 3-4 surface ruptures; subsequent deepening of the trench by McCalpin (2006) indicates that no strata correlate between the exposed portions of the hanging and foot walls. His slip rates are slightly greater than 0.1 mm/yr but he also indicated that there is possible backtilting. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Comments

The preferred vertical slip rate is based on three of the twenty-one scarp profiles (Machette, 1987). Two profiles gave 30.3 and 34.8 m heights for offsets of the Jornada I surface, which Machette estimated to be 350 +/- 50 ka. From these data he calculated minimum slip rates of 0.08-0.1 mm/yr since 350 ka. A third profile yielded a 59.6 m height for an offset of the Camp Rice Formation, which he estimated to be approximately 500 ka, for a slip rate of 0.12 mm/yr since 500 ka. The only trench across the fault revealed evidence of 3-4 surface ruptures; subsequent deepening of the trench by McCalpin (2006) indicates that no strata correlate between the exposed portions of the hanging and foot walls. His slip rates are slightly greater than 0.1 mm/yr but he also indicated that there is possible backtilting. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
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. McCalpin, J.P., 2006, Quaternary faulting and seismic source characterization in the El Paso-Juarez metropolitan area—Collaborative research with the University of Texas at El Paso: Final Technical Report submitted to U.S. Geological Survey under Contract 03HQGR0056, April 26, 2006, 68 p, http://earthquake.usgs.gov/research/external/reports/03HQGR0056.pdf. Machette, M.N., 1987, Preliminary assessment of paleoseismicity at White Sands Missile Range, southern New Mexico—Evidence for recency of faulting, fault segmentation, and repeat intervals for major earthquakes in the region: U.S. Geological Survey Open-File Report 87-444, 46 p.

Selected References

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.
McCalpin, J.P., 2006, Quaternary faulting and seismic source characterization in the El Paso-Juarez metropolitan area—Collaborative research with the University of Texas at El Paso: Final Technical Report submitted to U.S. Geological Survey under Contract 03HQGR0056, April 26, 2006, 68 p, http://earthquake.usgs.gov/research/external/reports/03HQGR0056.pdf.
Machette, M.N., 1987, Preliminary assessment of paleoseismicity at White Sands Missile Range, southern New Mexico—Evidence for recency of faulting, fault segmentation, and repeat intervals for major earthquakes in the region: U.S. Geological Survey Open-File Report 87-444, 46 p.