The largest inland earthquake in North America in almost 150 years struck Alaska on November 3, 2002. It ruptured three different faults ending with a total rupture length of ~330 km. It started on the previously unrecognized Susitna Glacier Thrust fault, a splay fault south of the McKinley strand of the Denali fault system (DFS). Then the rupture transferred onto the main strand of the DFS and continued as a right-lateral strike-slip event for ~220 km until it reached the Totschunda fault near 143oW longitude. At that point, it right-stepped onto the more south-easterly trending Totschunda fault and stopped after rupturing nearly 70 km of it. A team of geologists surveyed the total length of the ruptured faults and reported maximum vertical offsets on the Susitna Glacier Thrust of 4 m and maximum horizontal offsets of 8.8 m west of the Denali and Totschunda fault junction. The estimated magnitude of this earthquake ranges from the body wave magnitude mb of 7.0 to the moment magnitude MW of 7.9 to the surface wave magnitude MS of 8.5. While the fault rupture lasted for approximately 100 sec from its initiation to the arrest, its distal effects were felt for many days. Of the population centers, the hardest hit were the villages of Mentasta and Northway, located at the eastern end of the rupture zone. This event caused significant damage to the transportation systems in central Alaska. The Trans-Alaska Pipeline suffered some damage, but no oil spills occurred. Multiple land slides and rock avalanches occurred in the Alaska Range with the largest slide on the Black Rapids Glacier. The Denali Fault event was felt as far as Washington and caused seiches in pools and lakes as far as Texas and Louisiana. There were reports of triggered seismicity in volcanic and geothermal centers in Washington and California and regional seismicity in Utah. The M 7.9 Denali Fault event was preceded by the magnitude 6.7 Nenana Mountain event on October 23, 2002. Its epicenter was located on the Denali fault 22 km east of the M 7.9 event epicenter. In response to the magnitude 6.7 and 7.9 events, the Alaska Earthquake Information Center (AEIC) staff installed a network of temporary instruments for the aftershock monitoring. The temporary network was dismantled in June, 2003.
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This high-altitude view shows the approximate locations of the earthquake epicenters. The view is eastward along the main strand of the Denali fault, which is marked here by a prominent linear valley along the southern edge of the Alaska Range. In the left foreground, the Nenana River marks the eastern boundary of Denali National Park. The Parks Highway, which connects Anchorage and Fairbanks, lies immediately east of the river north of the fault, but diverges from the river to the south. The epicenter of the November 3 earthquake was approximately 42 miles (68 km) east of the highway. In the distance, the rugged peaks of Mts. Deborah and Hess rise to about 12,000 feet (3650 m) just north of the epicenters and the bend in the Denali fault. (Photo and interpretation by Wesley K. Wallace, Geophysical Institute, University of Alaska Fairbanks)
Follow this link to see the full resolution version of this photo.
Earthquake parameters:Origin Time (UT): 11/03/2002 22:12:41.52
Depth: 4.20 km
Magnitude: MW 7.9, MS 8.5, ML 7.2, mb 7.0
First motions focal mechanism:Paz=335; Ppl=0; Taz=244; Tpl=72
strike1=262; dip1=48; rake1=115; strike2=47; dip2=48; rake2=65
The Nenana Mountain and Denali Fault earthquakes generated a vigorous aftershock sequence. The AEIC located over 1,000 aftershocks of the M 6.7 event prior to the M 7.9 mainshock and over 35,000 aftershocks through the end of 2004. Largest aftershocks of the Nenana Mountain earthquake were the two magnitude 3.8 events. A magnitude 4.4 foreshock preceded the Denali Fault mainshock by 3.5 hours. The largest aftershock (M 5.8) occurred 20 minutes after the main shock and was located 95 km east of the mainshock's epicenter (~10 km east of the Richardson highway crossing). Following the Denali Fault earthquake, the analyst processing load increased from an average of 40 events per day in September to an average of over 400 events per day in November. The onslaught of the data has created processing delays. Additional delays have been caused by the necessity of reviewing the earthquake locations a second time when the data from the temporary Denali network were brought back from the field and merged with the bulk of AEIC data. Four month of data remain unprocessed at this time (January-April, 2003). The magnitude of completeness mc of the aftershock catalog varies along the rupture zone. While on average for October-December data mc is 1.4, it is as low as 1.1 at the western end of the rupture and as high as 2.2 at the eastern end .
||white line - mapped rupture;
red lines - fault traces;
dashed black line - Trans-Alaska Pipeline;
black lines - roads;
blue lines - major rivers
A GPS crew visiting earthquake site on Nov.4 observed sand blows on a baseball field in Northway (photos).
Bill Perkins from Shannon & Wilson, Seattle and S&W Fairbanks office have been visiting sites damaged during M7.9 earthquake. You can find photos from this post-earthquake reconnaissance on this website.
Road offset, Richardson Hwy. Milepost 215.5 on the Richardson Highway. The direction of view is approximately from north to south. The fault trace is running almost NW-SE direction. The horizontal offset is approximately 2-2.5m. Photo courtesy: Akihiko Ito Dr.Sci, Associate professor, Utsunomiya University, Japan.
Photos from Alaska DGGS reconnaissance works.
Photos along the Denali and Totschunda faults by Wes Wallace, Professor of Geology at the UAF.
Photos from Peter Haeussler, Geologist at the Anchorage office of the U.S. Geological Survey.
In December, 2002, scientists gathered for a special session on the Denali Fault earthquake sequence at the Fall Meeting of the American Geophyscial Union in San Francisco, CA. Fourty three papers were presented regarding different aspects of the M7.9 earthquake.
Seismological Society of America published BSSA Dedicated Issue: The 2002 Denali Fault Earthquake Sequence, V.94, N.6B, 2004.
A. Bilich, J.F. Cassidy, and K.M. Larson, GPS seismology: Application to the 2002 Mw 7.9 Denali Fault earthquake, Bull. Seism. Soc. Am., 98(2), 593-606, doi:10.1785/0120070096, 2008.
B.-Ye. Liao and H.-Ch. Huang, Rupture process of the 2002 Mw 7.9 Denali earthquake, Alaska, using a newly devised hybrid blind deconvolution method, Bull. Seism. Soc. Am., 98(1), 162-179, doi:10.1785/0120050065, 2008.
Bufe, C.G., Coulomb stress transfer and tectonic loading preceding the 2002 Denali Fault earthquake, Bull. Seism. Soc. Am., 96(5), 1662-1674, doi:10.1785/0120050007, 2006.
Barberopoulou, A., A. Qamar, T.L. Pratt, and W.P. Steele, Long-period effects of the Denali earthquake on water bodies in the Puget lowland: Observations and modeling, Bull. Seism. Soc., 96 (2), doi:10.1785/0120050090, 519-552, 2006.
Hreinsdottir, S., J.T. Freymueller, R. Burgmann, and J. Mitchell, Coseismic deformation of the 2002 Denali fault earthquake: Insights from GPS measurements, J. Geophys. Res., 111 (B03308), doi:10.1029/2005JB003676, 2006.
Asano, K., T. Iwata, and K. Irikura, Estimation of source rupture process and strong ground motion simulation of the 2002 Denali, Alaska, earthquake, Bull. Seism. Soc., 95, 1710-1715, doi:10.1785/0120040154, 2005.
Barberopoulou, A., A. Qamar, T.L. Pratt, K.C. Creager, and W.P. Steele, Local amplification of seismic waves from the Mw 7.9 Alaska earthquake and damaging water waves in Lake Union, Seattle, Washington, Geophys. Res. Lett., 31 (L03607), doi:10.1029/2003GL0185690, 2004.
Anderson, G., and C. Ji, Static stress transfer during the 2002 Nenana Mountain-Denali Fault, Alaska earthquake sequence, Geophys. Res. Lett., 30 (6), 1310, doi:10.1029/2002GL016724, 2003.
Ducic, V., J. Artru, and P. Lognonne, Ionospheric remote sensing of the Denali Earthquake Rayleigh surface waves, Geophys. Res. Lett., 30 (18), 1951, doi:10.1029/2003GL017812, 2003.
Ebehart-Phillips, D., P.J. Haeussler, J.T. Freymueller, A.D. Frankel, C.M. Rubin, P. Craw, N.A. Ratchkovski, G. Anderson, A.J. Crone, T.E. Dawson, H. Fletcher, R. Hansen, E.L. Harp, R.A. Harris, D.P. Hill, S. Hreinsdottir, R.W. Jibson, L.M. Jones, D.K. Keefer, C.F. Larsen, S.C. Moran, S.F. Personlus, G. Plafker, B. Sherrod, K. Sieh, and W.K. Wallace (2003). The 2002 Denali Fault earthquake, Alaska: A large magnitude, slip-partitioned event, Science, 300, 1113-1118.
Hreinsdottir, S., J.T. Freymueller, H.J. Fletcher, C.F. Larsen, and R. Burgmann, Coseismic slip distribution of the 2002 MW 7.9 Denali fault earthquake, Alaska, determined from GPS measurements, Geophys. Res. Lett., Vol. 30, No. 13, 1670, doi:10.1029/2003GL017447, 2003.
Larson, K.M., P. Bodin, and J. Gomberg, Using 1-Hz GPS data to measure deformation caused by the Denali Fault earthquake, Science, 300, 1421-1424, 2003.
Lu, Z., T. Wright, and C. Wicks, Deformation of the 2002 Denali Fault ertahquakes, Alaska, mapped by Radarsat-1 interferometry, EOS, 2003.
Ozacar, A.A., S.L. Beck, and D.H. Christensen, Source process of the 3 November 2002 Denali fault earthquake (central Alaska) from teleseismic observations, Geophys. Res. Lett., 30 (12), 1638, doi:10.1029/2003GL017272, 2003.
Ratchkovski, N.A., Change in stress directions along the central Denali fault, Alaska after the 2002 earthquake sequence, Geophys. Res. Lett., Vol. 30, doi:10.1029/2003GL017905, 2003.
Ratchkovski, N.A., R.A. Hansen, J.C. Stachnik, T. Cox, O. Fox, L. Rao, E. Clark, M. Lafevers, S. Estes, J.B. MacCormack, and T. Williams, Aftershock sequence of the Mw 7.9 Denali Fault, Alaska, earthquake of 3 November, 2002 from the regional seismic network data, Seism. Res. Lett., Vol. 74, No. 6, 2003.
Wright, T.J., Z. Lu, and C. Wicks, Source model for the Mw 6.7, 23 October 2002, Nenana Mountain Earthquake (Alaska) from InSAR, Geophys. Res. Lett., Vol. 30, No. 18, 1974, doi:10.1029/2003GL018014, 2003.
Masayuki KIKUCHI & Yoshiko YAMANAKA from the Earthquake Information Center, Earthquake Res. Inst., Univ. of Tokyo, JAPAN, obtained the source rupture processes of the 7.9 earthquake of Nov. 3, 2002, infered from the teleseismic body waves. Follow this link to see results of their inversion.
USGS fact sheet on the 7.9 event.
Macroseismic Survey of the Denali Fault Earthquake.