2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Helvetia fault	Oregon

GEOMETRY
Dip (degrees)	60
Dip direction	NE
Sense of slip	reverse
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	90
Length (km)	14

MODEL VALUES
Probability of activity	1
Minimum magnitude	n/a
Maximum magnitude	6.40
b-value	n/a

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value
60	0.02	17.3	2.56e-05	n/a

Comments
The assigned vertical slip rate is based on 20 m of vertical separation of the upper part of late Miocene-early Pleistocene sediments considered to be 11 Ma-750 ka (Geomatrix Consultants, Inc., 1995). The characteristic magnitude for this fault is fixed at M6.5 based on Basin and Range Province Earthquake Working Group recommendations documented by Lund (2006) even though the length of the fault would suggest a smaller earthquake.

Comments

The assigned vertical slip rate is based on 20 m of vertical separation of the upper part of late Miocene-early Pleistocene sediments considered to be 11 Ma-750 ka (Geomatrix Consultants, Inc., 1995). The characteristic magnitude for this fault is fixed at M6.5 based on Basin and Range Province Earthquake Working Group recommendations documented by Lund (2006) even though the length of the fault would suggest a smaller earthquake.

Selected References
Geomatrix Consultants, Inc., 1995, Seismic design mapping, State of Oregon: Technical report to Oregon Department of Transportation, Salem, Oregon, under Contract 11688, January 1995, unpaginated, 5 pls., scale 1:1,250,000. 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.

Selected References

Geomatrix Consultants, Inc., 1995, Seismic design mapping, State of Oregon: Technical report to Oregon Department of Transportation, Salem, Oregon, under Contract 11688, January 1995, unpaginated, 5 pls., scale 1:1,250,000.
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.