Magnitude 1.4 - 25 miles N of Koyukuk

Tectonic Setting of Interior Alaska

Interior Alaska seismicity reflects transpression and block rotation. Three different types of tectonic structures contribute to generating seismicity in this region: right-lateral strike slip faults (Denali, Tintina, Kaltag), north-northeast-trending seismic zones (Minto, Fairbanks, Salcha, Dall City, Rampart), and thrust faults in the northern foothills of the Alaska Range. The largest event recorded in the Interior was the 1937 M7.3 Salcha earthquake. It produced extensive ground failures in the epicentral area, but there was no documented evidence of surface rupture. Other notable events include the 1968 M7.1 Rampart, 1985 M6.1 Dall City, and 1995 M6.0 Minto Flats earthquakes. The Fairbanks Seismic Zone was the site of three M5-6 earthquakes in 1967. A M7.2 thrusting event occurred in 1947 at the front edge of the northern foothills of the Alaska range and south of the Salcha Seismic Zone. This event along with current seismic activity is indicative of ongoing thrusting deformation on the north side of the central Alaska Range. East of longitude 146°W, the seismic activity between the Tintina Fault to the north and the Denali Fault to the south decreases considerably.