The most powerful recorded earthquake in North American history struck Alaska on March 27, 1964, with a moment magnitude of 9.2. The earthquake and the multiple tsunamis it generated caused widespread damage in Alaska and beyond. In Alaska alone, tsunamis caused over $80 million in damage and were responsible for over 90 percent of earthquake-related deaths.

Tsunamis are formed by the sudden displacement of a large volume of water. In the case of the 1964 earthquake, the main tsunami was generated by the vertical displacement of water caused by the movement of the North American plate over the Pacific plate. The sudden upward movement of the seafloor generated powerful tsunami waves that carried tremendous destructive energy. Tsunamis can travel long distances without losing much energy and can therefore cause destruction far from their point of origin. The 1964 tsunami that originated in Alaska caused considerable damage in western Canada, Oregon, Washington, and California; its effects were also felt in other parts of the Pacific (including Hawaii and Japan).

In addition to this ocean-wide tsunami created by displacement along the plate boundary, the 1964 earthquake also resulted in local tsunamis at Valdez, Seward, Whittier, and Kachemak Bay in Alaska that were generated by local events such as landslides (both underwater landslides and coastlands that fell into the sea). For example, the shaking earth caused a large section of the Seward coast to fall into Resurrection Bay and produced a tsunami that destroyed much of the waterfront. These types of tsunamis are destructive locally, but do not travel across the ocean.

Many conditions can affect the severity of damage from a tsunami. For instance, the effects of tsunami waves increase when the waves coincide with storm surges or high tides. Local geography also plays a role in the severity of the tsunami. The 1964 tsunamis were especially damaging in Prince William Sound because the waves were confined to the relatively narrow body of water and reverberated in the region for hours; maximum inundation occurred at high tide several hours after the earthquake. Tsunami warning centers in coastal communities constantly monitor the oceans and seismic events in an effort to minimize damage by predicting when and where a tsunami could strike. Countless lives are saved by tsunami warning systems and evacuation plans that rapidly and safely move local residents to higher ground.

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