2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
West Lobo Valley fault zone	Texas

GEOMETRY
Dip (degrees)	40/50/60
Dip direction	E
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	61

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.15
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.05	23.3	3.82e-05	0.732	0.2
50	0.04	19.6	2.69e-05	0.580	0.6
60	0.04	17.3	2.10e-05	0.473	0.2

Comments
The fault zone has four sections, and the section lengths and vertical offsets appear to increase from north to south. Along all sections, the faulted deposits are middle Pleistocene that are 130-500 ka (Collins and Raney, 1993). The preferred vertical slip rate is the average of the maximum and minimum slip rates from the two middle sections; the maximum rate comes from the south-central section and the minimum comes from the north-central section. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Comments

The fault zone has four sections, and the section lengths and vertical offsets appear to increase from north to south. Along all sections, the faulted deposits are middle Pleistocene that are 130-500 ka (Collins and Raney, 1993). The preferred vertical slip rate is the average of the maximum and minimum slip rates from the two middle sections; the maximum rate comes from the south-central section and the minimum comes from the north-central section. 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. Collins, E.W., and Raney, J.A., 1993, Late Cenozoic faults of the region surrounding the Eagle Flat study area, northwestern trans-Pecos Texas: Technical report to Texas Low-Level Radioactive Waste Disposal Authority, under Contract IAC(92-93)-0910, 74 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.
Collins, E.W., and Raney, J.A., 1993, Late Cenozoic faults of the region surrounding the Eagle Flat study area, northwestern trans-Pecos Texas: Technical report to Texas Low-Level Radioactive Waste Disposal Authority, under Contract IAC(92-93)-0910, 74 p.