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Glacier Effects of the M7.9 Denali Fault Earthquake of November 3, 2002
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Avalanches cover 13 sq. km. of lower Black Rapids Glacier. Photo
on Nov. 7, 2002 by R. March, USGS. |
On November 3, 2002 a magnitude 7.9 earthquake struck the Denali Fault in
central Alaska. It was the largest earthquake in the United States since 1986 and ties for the
9th largest earthquake in the United States in the last 200 years (top 15 list). The earthquake
ruptured 260 kilometers of the Denali Fault with measured offsets as much as 8 meters as of
this writing. The fault is of interest to glaciologists because 130 kilometers, or about
half, of the rupture lies under glaciers. The fault rupture crosses the West Fork, Susitna, Black
Rapids, Canwell, Gakona, Chistochina, and numerous smaller glaciers. |
November 7 Flight Observations
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Double fault trace running down upper West Fork
Chistochina Glacier. Photo on Nov. 7, 2002 by R. March, USGS. |
On November 7, 2002
Dennis Trabant and
Rod March (US Geological Survey,
Fairbanks, AK), and Dr. Martin Truffer
(University of Alaska, Geophysical Institute, Fairbanks, AK) flew by fixed wing Cessna 206 to document the effects of the Nov. 3, 2002
magnitude 7.9 Denali Fault earthquake. We were able to fly and photograph the fault trench
from near Cantwell to just NW of Mentasta Lake and additionally south of the fault trench
between the Richardson Highway and Susitna Glacier to observe the areas around Eureka,
Maclaren, and East Fork Glaciers. The north flank of the central and eastern Alaska Range was
obscured by clouds and was not investigated. Deep shadows due to low sun angles made some
areas difficult to see and photograph. Features observed and photographed
included numerous rock, snow, and ice avalanches, single linear faults, sub-parallel linear
fault pairs, shear zones with multiple sub parallel faults, long curved faults that appear to
follow glacial structures, zigzag faults, at least one significant fault perhaps 1 km south of
the Denali Fault that was not parallel to the Denali Fault trench, odd looking holes on a
glacier surface along the main fault that may be surrounded by blast debris, avalanche-debris
dammed lakes both on and off glaciers, numerous small glacier surficial lakes that had
drained, cracking in lake ice, glacier cracks that indicate drainage of subglacial lakes
(these may be pre-quake features), dark rims around lakes that may have been evidence of
seiches. The most dramatic features by far were the very large, mostly rock avalanches onto
Black Rapids and the very large glacier collapse/avalanche onto Gakona Glacier.
Map and Photo galleries arranged by 8 regions along
the fault rupture.
Detailed chronological description of
flight observations.
Reports
Truffer, M., Craw, P., Trabant, D., March, R. , Effects of the M7.9 Denali Fault Earthquake on
glaciers in the Alaska Range, Eos Trans. AGU, 83(47), Fall Meet. Suppl., Abstract S72F-1334
Poster [abstract and poster]
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Other sites about this earthquake:
State of
Alaska, Division of Geological and Geophysical Surveys
University of Alaska, Geophysical Institute,
Alaska Earthquake Information Center
US Geological Survey
Earthquake Hazards Program
Maintainer: Rod
March
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Last update:
Wednesday, January 03, 2007 12:46 PM
URL: http://ak.water.usgs.gov/glaciology/m7.9_quake/index.htm
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