Puget Sound area, Washington
1965 04 29 15:28:43.7 UTC
This earthquake caused about $12.5 million in property damage and killed seven people. This shock was characterized by a rather large area of MM intensity VII and small pockets of MM intensity VIII in Seattle and suburbs and southeast of Seattle, in Issaquah. Pockets of high earthquake intensity, as typified by damage such as fallen chimneys, almost always were associated with variations in the local geology.
Chimneys were damaged extensively in West Seattle, and two schools were damaged severely. The low-lying and filled areas along the Duwamish River and its mouth settled, causing considerable building damage. Harbor Island, at the mouth of the Duwamish River, was severely damaged. Slumping occurred along a steep slope near Admiral Way. A brick garage partly collapsed at Issaquah; one school was damaged extensively; and chimneys in the area sustained heavy damage. Many instances of parapet and gable failure occurred. Damage to utilities in the area was not severe.
In general, damage patterns repeated those observed in the April 1949 shock, although the 1949 event was more destructive. Buildings apparently damaged in 1949 often sustained additional damage in 1965. An example is the Alki Beach section of West Seattle, where almost every chimney was knocked down in 1965. Similar damage occurred there in the 1949 earthquake.
Buildings having unreinforced brick-bearing walls with sand-lime mortar were damaged most severely. Multistory buildings, however, generally had slight or no damage. Performance of wood frame dwellings almost always was excellent, and, where damage occurred, it was confined mainly to cracks in plaster or to failure of unreinforced brick chimneys at or above the roofline. Also felt in Idaho, Montana, Oregon, and in British Columbia, Canada. Little aftershock activity was observed.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.