2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Happy Camp fault	Oregon

GEOMETRY
Dip (degrees)	60
Dip direction	N
Sense of slip	reverse
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	90
Length (km)	20

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	6.58
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value
60	0.03	17.3	3.55e-05	0.842

Comments
The Happy Camp fault was misidentified as the Netarts Bay fault in 1996. We follow the established usage of the name as summarized in the Quaternary fault and fold database for Oregon. The fault is known only from its 3-km-long exposure in coastal sea cliffs. The observed offset of Quaternary sediments on the fault is inconsistent with its being as short as 3 km. Accordingly, we followed Geomatrix Consultants, Inc. (1995) in assigning a length of 20 km. The assigned vertical slip rate is based on 9-m offset of Pleistocene channel deposits that are probably 200 ka to 1.6 Ma (Geomatrix Consultants, Inc., 1995).

Comments

The Happy Camp fault was misidentified as the Netarts Bay fault in 1996. We follow the established usage of the name as summarized in the Quaternary fault and fold database for Oregon. The fault is known only from its 3-km-long exposure in coastal sea cliffs. The observed offset of Quaternary sediments on the fault is inconsistent with its being as short as 3 km. Accordingly, we followed Geomatrix Consultants, Inc. (1995) in assigning a length of 20 km. The assigned vertical slip rate is based on 9-m offset of Pleistocene channel deposits that are probably 200 ka to 1.6 Ma (Geomatrix Consultants, Inc., 1995).

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.