A field report on the Alaska earthquakes of April 7, 1958

The Alaska earthquake at 0530 on April 7, 1958 (150° WMT) was the largest (Richter scale $7−712$⁠) of a series of shocks centered in an area near Huslia, Alaska. The field epicenter located at 65° 45'N, 155° 45'W lies in the Koyukuk Basin where arrested sand dune deposits cover a part of the near-level alluvium deposited by the Koyukuk River. Extensive fracturing occurred in the lake and river ice in the epicentral area and the sand dune deposits were heavily fissured. The most severe damage occurred in a zone approximately 10 miles wide by 40 miles long trending northeast from Huslia. Associated with the sand dunes in this zone were large deposits of silt and sand which flowed to the surface from the alluvium beneath the dunes. Because of the distinctive characteristics of these flows they have been termed sand flows to distinguish them from mud flows and sand blows. Associated with the sand flows were surface collapses resulting in near-conical pits as much as 30 feet deep and up to 120 feet in diameter. The earthquakes caused little monetary damage, although the main shock registered a Modified Mercalli intensity V or more over an area in excess of 100,000 square miles.