2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Organ Mountains fault	New Mexico

GEOMETRY
Dip (degrees)	60/40/50
Dip direction	E
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	30

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	6.79
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.23	23.3	2.81e-04	1.679	0.2
50	0.20	19.6	1.98e-04	1.526	0.6
60	0.17	17.3	1.55e-04	1.420	0.2

Comments
The Organ Mountains fault was assigned a vertical slip rate of 0.15 mm/yr in the 1996 and subsequent national seismic-hazard maps. The source of this rate is unknown. The documentation of the 1996 slip rates attributes the 0.15 mm/yr value to Machette (1987), but this report contains no data from which the 0.15 value could be calculated in any straightforward manner. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Comments

The Organ Mountains fault was assigned a vertical slip rate of 0.15 mm/yr in the 1996 and subsequent national seismic-hazard maps. The source of this rate is unknown. The documentation of the 1996 slip rates attributes the 0.15 mm/yr value to Machette (1987), but this report contains no data from which the 0.15 value could be calculated in any straightforward manner. 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. 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.
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.