The 1964 Tsunami in Crescent City, California: A 40-year retrospective

摘要

The March 1964 Alaska tsunami caused major damage in Alaska and also impacted the west coast of North America. Crescent City, 3000 km away from the source region, suffered the greatest damage outside Alaska. At least four observable waves hit the area and peak tsunami run-up was 6.7 m relative to Mean Lower Low Water ((MLLW). Thirty blocks of the downtown and harbor areas were inundated and nearly 300 homes and businesses damaged or destroyed. We reexamine pre- and post-tsunami air photos, damage assessments and personal accounts to describe tsunami flow characteristics, inundation and structural damage. Eyewitnesses generally described the incoming water as a gentle flow with water elevation increasing at the rate of about 0.3 meters/minute. The peak water elevation in the developed parts of the City reached about 3 meters above the land surface. In areas where the water depth was one meter or greater, the most common cause of structural damage was floating wooden houses off foundations. Other structures were damaged by the impact of debris and moving structures, and/or walls buckling from internal water pressure after the water receded. Fires ignited gasoline tanks and spread to neighboring structures. Most of the buildings within the inundation zone were subsequently demolished through the Crescent City Redevelopment Project. In the forty years since the tsunami, Crescent City has established a siren-based tsunami warning system and developed tsunami evacuation maps, posted signs along evacuation routes and is the only city in California currently designated "Tsunami Ready" by the National Weather Service's TsunamiReady program. However offsetting these mitigation efforts is the increased exposure caused by new commercial development within the 1964 inundation zone and recognition of the Cascadia subduction zone as a source of significantly larger tsunamis than the 1964 event.