This wave was caused by a magnitude 7.1 submarine earthquake. In 1964 there was a magnitude 9.2 quake in Alaska. Four hours later the first waves arrived in Crescent City, California. Within six hours even bigger waves arrived. Ten people were killed.
Tidal waves are actually misnamed.
They are not caused by tides. Not all submarine earthquakes cause tsunami. The January 13th Pacific Ocean earthquake off the coast of San Salvador, registering 7.6 on the Richter scale, did not cause any ocean disturbance. Tsunami are very hard to detect, since they cannot be seen when they are in the deep ocean. As the tsunami reaches shallow water, its speed decreases, but the energy it contains remains about the same.