WEST-COAST TIDES DURING CASCADIA SUBDUCTION ZONE TSUNAMIS

Low, neap tides occurred along the West Coast of the United States and Canada around 0500 UT January 27, 1700, a time for the last major Cas cadia earthquake/tsunami based on teletsunami arrival times in Japan [ Satake et al., 1996]. However, high-range perigean spring tides occurr ed only a week later, illustrating how accurately occurrence times mus t be known to constrain the region's background water levels during su ch events. The ranges of background water levels increase northward fr om 3 m at Monterey to 8.5 m at Queen Charlotte, as estimated from the amplitudes of perigean spring tides and subtidal winter fluctuations.