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A mass failure model for the initial degradation of fault scarps, with application to the 1959 scarps at Hebgen Lake, Montana

Lewis Kogan and Rebecca Bendick
A mass failure model for the initial degradation of fault scarps, with application to the 1959 scarps at Hebgen Lake, Montana
Bulletin of the Seismological Society of America (February 2011) 101 (1): 68-78

Abstract

Calculation of earthquake scarp ages from scarp morphology usually assumes that scarp materials reach their angle of repose immediately after a rupture. However, observations of the 1959 Hebgen Lake, Montana, earthquake scarp and similar features worldwide confirm that scarps require a finite period of mass failure to reach the initial conditions for hillslope diffusion, so the age of features less than 1000 yr old cannot be accurately estimated with methods based only on the linear diffusion equation. We apply a numerical model of this interval of mass failure degradation to vertical initial-angle scarps from the 1959 rupture at Hebgen Lake, Montana. The mass failure rate coefficient, R (sub M) , ranges from 1.0X10 (super -2) to 1.2X10 (super -1) m.yr (super -1) for young scarps at Hebgen Lake and nine other locations, and has little or no dependence on climate conditions such as annual temperature range or average rainfall. Including an interval of mass failure gives more accurate age estimates where a scarp age is of the same order as the characteristic mass failure relaxation time of 10-1000 yr.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 101
Serial Issue: 1
Title: A mass failure model for the initial degradation of fault scarps, with application to the 1959 scarps at Hebgen Lake, Montana
Affiliation: University of Montana, Department of Geosciences, Missoula, MT, United States
Pages: 68-78
Published: 201102
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 46
Accession Number: 2011-026445
Categories: Quaternary geologySeismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N44°45'00" - N44°45'00", W111°15'00" - W111°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201115
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