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 Cascadia earthquake/tsunami based on teletsunami arrival times in Japan [Satake et al., 1996]. However, high-range perigean spring tides occurred only a week later, illustrating how accurately occurrence times must be known to constrain the region's background water levels during such events. The ranges of background water levels increase northward from 3 m at Monterey to 8.5 m at Queen Charlotte, as estimated from the amplitudes of perigean spring tides and subtidal winter fluctuations.