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Documentation of seven earthquakes over the past approximately 7000 years on the west-central Denali Fault at the Nenana River, Alaska

J. Kade Carlson, Sean P. Bemis, Nathan Toke, Bradley Bishop and T. Patrick Taylor
Documentation of seven earthquakes over the past approximately 7000 years on the west-central Denali Fault at the Nenana River, Alaska
Bulletin of the Seismological Society of America (February 2018) 108 (1): 84-100

Abstract

The Denali fault in south-central Alaska is a major right-lateral strike-slip fault that parallels the Alaska Range for much of its length and represents the largest seismogenic source for interior Alaska. The fault system is over 1200 km in length, and identification of paleoseismic sites that preserve more than 2-3 paleoearthquakes has proven challenging due to its remote location and difficulty of access. In 2012 and 2015, we developed the Dead Mouse site, which provides the first long paleoearthquake record west of the 2002 Mw 7.9 Denali fault earthquake sequence rupture extent. This site is located on the west-central segment of the Denali fault near the southernmost intersection of the Parks Highway and the Nenana River. We hand-excavated three fault-perpendicular trenches and documented new evidence for seven surface-rupturing paleoearthquakes from deformation in the upper 2.5 m of stratigraphy. Evidence for these events includes offset units, filled fissures, upward fault terminations, and an angular unconformity. Chronological constraints from Bayesian sequence modeling of radiocarbon ages and one tentative tephra correlation indicate these seven earthquakes occurred at 388 cal B.P. (442-319; E1), 807 cal B.P. (853-764; E2), 1282 cal B.P. (1392-1160; E3), 2652 cal B.P. (2805-2460; E4), 3402 cal B.P. (3790-3010; E5*), 5673 cal B.P. (6676-4632; E6*), and 6987 cal B.P. (7281-6668; E7*). Although there are likely missing earthquakes in our chronology prior to E4, the intervals between E1 and E4 suggest significant variability in recurrence period at the Dead Mouse site. Additional paleoearthquake chronologies at neighboring sites are required to make reliable estimates of the spatial and temporal rupture history for the west-central Denali fault, but our data demonstrate the potential for recurrence periods as short as 300-600 yrs, well within range of the current open interval for the Denali fault at the Nenana River.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 108
Serial Issue: 1
Title: Documentation of seven earthquakes over the past approximately 7000 years on the west-central Denali Fault at the Nenana River, Alaska
Affiliation: University of Kentucky, Department of Earth & Environmental Sciences, Lexington, KY, United States
Pages: 84-100
Published: 201802
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 48
Accession Number: 2018-052095
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 4 tables, sketch maps
N62°00'00" - N64°00'00", W149°00'00" - W146°00'00"
Secondary Affiliation: Utah Valley University, USA, United StatesBrigham Young University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2018
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