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Late Quaternary slip rate and seismic hazards of the West Klamath Lake fault zone near Crater Lake, Oregon Cascades

Geology

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Abstract

Crater Lake caldera is at the north end of the Klamath graben, where this N10??W-trending major Basin and Range structure impinges upon the north-south-trending High Cascades volcanic arc. East-facing normal faults, typically 10-15 km long, form the West Klamath Lake fault zone, which bounds the graben on its west side. The fault zone terminates on the south near the epicentral area of the September 1993 Klamath Falls earthquakes. It continues north past Crater Lake as the Annie Spring fault, which is within ~1 km of the west caldera rim, and Red Cone Spring fault. We have determined a long-term vertical slip rate of 0.3 mm/yr for these two faults using high-precision K-Ar and 40Ar/39Ar age measurements on offset lava flows ranging in age from ca. 35 to 300 ka. Holocene offset reported by Hawkins et al. and epicenters of eight MW 2 earthquakes in 1994 and 1995 indicate that the West Klamath Lake fautl zone is active. Empirical relations between earthquake magnitudes and scarp heights or fault lengths suggest that the fault zone is capable of producing earthquakes as large as MW 7 1/4 . Earthquakes on these or other faults of the zone could trigger landslides and rockfalls from the walls of the caldera, possibly resulting in large waves on Crater Lake.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Late Quaternary slip rate and seismic hazards of the West Klamath Lake fault zone near Crater Lake, Oregon Cascades
Series title:
Geology
Volume
27
Issue:
1
Year Published:
1999
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
43
Last page:
46