Effects of the Earthquake of March 27, 1964, at Valdez, Alaska

Abstract

Valdez is situated on the seaward edge of a large outwash delta composed of a thick Section of saturated silty sand and gravel. The earthquake of March 27, 1964, triggered a massive submarine slide, involving approximately 98 million cubic yards of material that destroyed the harbor facilities and nearshore installations. Waves generated by the slide and subsequent strong seiches did additional damage in the downtown area. Stresses generated by the seismic shocks and the slide developed an extensive system of fissures throughout the unconsolidated deposits at the head of the fiord. These fissures plus the shocks caused structural damage to many of the buildings in Valdez and destroyed the sewer and water systems. Removal of support from the face of the delta by submarine sliding allowed some of the material to move seaward and caused parts of the shore area to subside below high-tide level.

A site for relocating the town of Valdez has been designated. It is situated on the Mineral Creek fan—an area underlain by coarse alluvial gravel. This relocation site is protected from sea waves by a series of bedrock ridges and islands that also provide a resistant buttress retaining and protecting the toe of the fan from danger of sliding or slumping. The absence of evidence of ground breakage on the Mineral Creek fan indicates that the coarse subsoils at the relocation site react favorably under seismic conditions.

First posted October 17, 2012
Revised August 19, 2013