 As the largest earthquake in California since the 1989 Loma Prieta event several years earlier , the mainshock caused a non @-@ destructive tsunami that quickly reached the coast , and eventually Alaska and Hawaii several hours later . The tsunami was significant not because of its run @-@ up , but because of the speed with which it reached the coast and for how long the waves persisted . Other strong earthquakes have affected the same area , with some that were clearly associated with the ( interplate ) Mendocino Fracture Zone , and others ( like the two shocks on April 26 ) were intraplate earthquakes that ruptured within the Gorda Plate , but events that are unequivocally associated with the Cascadia subduction zone are very infrequent . 
