The Susitna Glacier thrust fault: Characteristics of surface ruptures on the fault that initiated the 2002 Denali fault earthquake

Bulletin of the Seismological Society of America
By: , and 

Links

Abstract

The 3 November 2002 Mw 7.9 Denali fault earthquake sequence initiated on the newly discovered Susitna Glacier thrust fault and caused 48 km of surface rupture. Rupture of the Susitna Glacier fault generated scarps on ice of the Susitna and West Fork glaciers and on tundra and surficial deposits along the southern front of the central Alaska Range. Based on detailed mapping, 27 topographic profiles, and field observations, we document the characteristics and slip distribution of the 2002 ruptures and describe evidence of pre-2002 ruptures on the fault. The 2002 surface faulting produced structures that range from simple folds on a single trace to complex thrust-fault ruptures and pressure ridges on multiple, sinuous strands. The deformation zone is locally more than 1 km wide. We measured a maximum vertical displacement of 5.4 m on the south-directed main thrust. North-directed backthrusts have more than 4 m of surface offset. We measured a well-constrained near-surface fault dip of about 19° at one site, which is considerably less than seismologically determined values of 35°–48°. Surface-rupture data yield an estimated magnitude of Mw 7.3 for the fault, which is similar to the seismological value of Mw 7.2. Comparison of field and seismological data suggest that the Susitna Glacier fault is part of a large positive flower structure associated with northwest-directed transpressive deformation on the Denali fault. Prehistoric scarps are evidence of previous rupture of the Sustina Glacier fault, but additional work is needed to determine if past failures of the Susitna Glacier fault have consistently induced rupture of the Denali fault.

Study Area

Publication type Article
Publication Subtype Journal Article
Title The Susitna Glacier thrust fault: Characteristics of surface ruptures on the fault that initiated the 2002 Denali fault earthquake
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120040619
Volume 94
Issue 6B
Year Published 2004
Language English
Publisher Seismological Society of America
Contributing office(s) Alaska Science Center
Description 18 p.
First page S5
Last page S22
Country United States
State Alaska
Other Geospatial Susitna Glacier thrust fault
Google Analytic Metrics Metrics page
Additional publication details