IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Oral Presentation 1773
Tsunami damage in Crescent City, California from the November 15, 2006
Kuril event
Prof. Lori Dengler
Geology Department Humboldt State University
Annabel Kelly, Burak Uslu, Aggeliki Barberopoulou, Solomon Yim
On November 15, the harbor at Crescent City in Del Norte County, California was hit by a series of
tsunami surges generated by the Mw = 8.3 Kuril Islands earthquake. The surges caused an estimated
$5.9 million in losses to the small boat basin, damaging the floating docks and several boats. The event
highlighted the vulnerability of harbors from a relatively modest tsunami, problems in with the tsunami
warning system for a marginal event, and the particular vulnerability of the Crescent City harbor area. It
also illustrated a persistent problem for tsunami hazard mitigation a lack of awareness of both
government officials and the public of the duration of tsunami hazard. Crescent City is particularly
susceptible to tsunami events. Twenty-four tsunamis have been recorded since 1938, nine with
amplitudes of 0.5 meters or larger including two previous events originating from the Kuril Islands. On
November 15, tsunami alert bulletins were issued by the North American Tsunami Warning Center in
Palmer, Alaska. When the alerts were cancelled at 6:40 AM PST, Crescent City had never been placed in
a warning or watch situation. Projections for tsunami amplitudes on the order of a meter prompted the
warning center to initiate an informal dialog with State Warning Centers and resulted in a local decision
to clear beaches and harbor areas in Humboldt and Del Norte Counties, California before the arrival of
the first expected wave at 11:48 AM PST. However there was no direct contact with the regional
weather forecast offices and no advice directly conveyed to local jurisdictions. Water level data from the
two previous Kuril events was not readily available to county emergency managers. There was
confusion at the local level about what amplitude meant, the duration of the event and the appearance
of a moderate tsunami in a harbor environment. Two people were on the docks believing the event was
over when the strongest surges (1.8 m peak to trough) arrived around 2:15 PM. They were fortunately
able to get to safety as the docks began breaking up. Wave activity continued with amplitudes on the
order of 0.5 m for more than 8 hours, through the next high tide cycle. As a result of the November 15
event, interim procedures were adopted by the Tsunami Warning Center to provide advice if forecasts
indicate that tsunami water heights may approach warning- level thresholds. On January 13, 2007 a
similar Kuril event occurred and hourly conferences between the warning center and regional weather
forecasts were held with a considerable improvement in the flow of information to local coastal
jurisdictions.
Keywords: tsunami, crescent city, mitigation