U.S. Geological Survey Photographic Library
ID. Alaska Earthquake no. 43ct
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Alaska Earthquake March 27, 1964. A subsidence trough (or graben) formed at the head of the L Street landslide in Anchorage during the earthquake. The slide block, which is virtually unbroken ground to the left of the graben, moved to the left. The subsidence trough sank 7 to 10 feet in response to 11 feet of horizontal movement of the slide block. A number of houses were undercut or tilted by subsidence of the graben. Note also the collapsed Four Seasons Apartment Building and the undamaged three-story reinforced concrete frame building behind it, which are on the stable block beyond the graben. Figure 18-A, U.S. Geological Survey Circular 491.
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