Reassessment of seismically induced, tsunamigenic submarine slope failures in Port Valdez, Alaska, USA

The M9.2 Alaska earthquake of 1964 caused major damage to the port facilities and town of Valdez, most of it the result of submarine landslide and the consequent tsunamis. Recent bathymetric multibeam surveys, high-resolution subbottom profiles, and dated sediment cores in Port Valdez supply new information about the morphology and character of the landslide deposits. A comparison of pre- and post-earthquake bathymetry provides an estimate of the net volume of landslide debris deposited in the basin and the volume of sediment removed from the source region. Landslide features include (1) large blocks (up to 40-m high) near the location of the greatest tsunamiwave runup (~50 m), (2) two debris lobes associated with the blocks, (3) a series of gullies, channels and talus, near the fjord-head delta and badly damaged old town of Valdez, and (4) the front of a debris lobe that flowed half-way down the fjord from the east end.