Tsunamis in the Pacific Northwest Tsunamis in the Pacific Northwest Tsunami triggers Tsunamis can be triggered by a variety of mechanisms. In the Pacific Northwest seismic triggers include subduction zone and crustal earthquakes. Earthquakes may also trigger submarine landslides producing local tsunamis. Crustal earthquakes Crustal earthquakes are more frequent and smaller in magnitude than subduction zone earthquakes, but may still produce tsunamis.
Earthquakes are common in the continental crust in the Pacific Northwest.
However, no earthquakes have been detected on the subduction thrust fault. Tsunami simulations have been made for large Cascadia subduction zone earthquakes. Documented examples from British Columbia include the collapse of a Maplegard Spit during the 1946 earthquake on Vancouver Island, a failure and tsunami at Tasu Inlet, Queen Charlotte Islands. Active fans and deltas are high-energy fluvial systems that are subject to continuous and progressive sediment loading. Where these deposits are underlain by soft muds they may be prone to large-scale slumps, earthflows, or flowslides.