Expected tsunami amplitudes and currents along the North American coast for cascadia subduction zone earthquakes

ABSTRACT

Tsunamis are numerically modeled using the nonlinear shallow-water equations for three hypothetical Cascadia subduction zone earthquakes. Maximun zero-to-peak tsunami amplitudes and currents are tabulated for 131 sites along the North American coast. Earthquake source parameters are chosen to satisfy known subduction zone configuration and thermal constraints. These source parameters are used as input to compute vertical sea-flood displacement. The three earthquakes modeled are moment magnitude 8.8, 8.5 and 7.8. Maximun zero-to peak tsunami amplitude for the Mw=8.8 earthquake is near 6 m normal to the fault break and maximum current is near3.5 m/s. Maximum amplitudes decrease by about one-half north and south of the fault break in the source region. Tsunami amplitudes vary along yhe Alaskan coast from less than 0.5 to 1.6 m. The modeled amplitudes for the Mw=8.8 quake decrease to less than 0.4 m south of Point Conception, CA. The Mw=7.8 earthquake generates a tsunami with a maximum amplitude of less than 1 m normal to the source (AU)