Mw 7.9 Denali Fault Earthquake

South face, Mt. Hayes. For more photos, see our photo slide show page...

The Denali fault earthquake that struck central Alaska area on November 3, 2002 ranks among the largest strike-slip ruptures of the past two centuries. Its length and slip magnitudes are comparable with those of the great California earthquakes of 1906 and 1857 and last year's Kokoxili earthquake along the Kunlun fault, Tibet.

 2003 field season photographs
 Press release: Mw 7.9 Denali Fault
 Photo slide show
 Geologic and geodetic slip distribution
 Alaska hazard map
 Science article

Earthquake Information

Our helicopter-supported reconnaisance investigations over a week-long period revealed three large ruptures with a total length of about 320 kilometers. The principal rupture was a 210-kilometer-long section of the Denali fault, with horizontal shifts of up to nearly 9 meters (26 feet). The epicenter of the main shock was located about 135 km south of Fairbanks.

Fault surface rupture in snow. For more photos, see our photo slide show page...

The rupture pattern is complex, with surface rupture beginning in the west along the Denali fault and extending to southeast on the Totschunda fault. Our initial observations reveal three distinct surface breaks with a combined rupture length of about 320 km.

Measuring surface offset. For more photos, see our photo slide show page...

The westernmost surface rupture is along 40 km of a previously unknown north-dipping thrust fault, named the Susitna Glacier fault. Here, vertical displacements average about 1.5 m and peak at 4-5 m.

Along the 210 km-long stretch of the Denali fault, dextral offsets average about 4 m and reach values as high as about 9 m, 170 km from the epicenter. Right-lateral slip drops dramatically from about 5 m to about 2 m across the broad stepover between the Denali and Totschunda faults; rupture continues to the southeast for about 75 km.

Additional Earthquake Information

The November 3rd earthquake was preceded by a Mw 6.7 foreshock on October 23, 2002 (Nenana Mountain earthquake) along the Denali fault. No surface rupture was associated with the October 23rd event. Sub-event 1 occurred along the newly recognized Susitna Glacier fault.

In 1932, three earthquakes (magnitude 6.0, 6.9 and 6.0) occurred on western part of the Denali fault. The largeset historic earthquake along the Denali fault occurred about 100 km east of the November 3rd earthquake. The Denali fault is characterized by infrequent large earthquakes, similar to the southern segments of the San Andreas fault in California.