Holocene slip rate for the western segment of the Castle Mountain fault, Alaska

Willis, J. B.; Haeussler, P. J.; Bruhn, R. L.; Willis, G. C.

Abstract:

The western segment of the Castle Mountain fault poses a significant seismic hazard to the most populated region of south-central Alaska. We identify a previously unrecognized margin of a postglacial outwash channel that is offset right laterally 36 ?? 4 m across the western segment of the Castle Mountain fault. This offset occurred after glaciers withdrew from the lowland 11,300-15,380 cal yr B.P. and after outwash channel margins were cut and stabilized 11,210-13,470 cal yr B.P. Using these ages and the measured separation, we obtain a maximum slip rate of 3.0 ?? 0.6 mm yr-1 and a minimum slip rate of 2.8 ?? 0.7 mm yr-1. These are the first lateral slip rates for the Castle Mountain fault established by a field measurement. Based on timing of the most recent earthquake, 670 ?? 60 yr B.P., the Castle Mountain fault could have accumulated an average single-event slip of about 1.9 m (extremes range from 1.3 to 2.6 m). The fault consists of two segments; a surface-rupturing earthquake likely will be limited to the 62-km-long western segment. Area-magnitude regression calculations suggest that such an earthquake on the western Castle Mountain fault would have a moment magnitude of 6.9 to 7.3.

Genre:

Article

ProdID:

70029749

Citation Author:

Willis, J. B.; Haeussler, P. J.; Bruhn, R. L.; Willis, G. C.

Citation Contributing Office:

Citation Datum:

Citation Day:

Citation Edition:

Citation Editor:

Citation End Page:

1024

Citation Issue:

Citation Keywords:

Citation Language:

English

Citation Larger Work Title:

Bulletin of the Seismological Society of America

Citation LatN:

Citation LatS:

Citation LonE:

Citation LonW:

Citation Month:

Citation No Pagination:

Citation Number Of Pages:

Citation Online Only Flag:

Citation Phsyical Description:

Citation Projection:

Citation Public Comments:

Citation Publisher:

Citation Series:

Citation Series Code:

Citation Series Number:

Citation Search Results Text:

Holocene slip rate for the western segment of the Castle Mountain fault, Alaska; 2007; Article; Journal; Bulletin of the Seismological Society of America; Willis, J. B.; Haeussler, P. J.; Bruhn, R. L.; Willis, G. C.