TIME AND MAGNITUDE
This earthquake has been recognized for its destructiveness, its duration and its extraordinary range of damages inflicted. On that Good Friday evening at approximately 30 kilometers beneath the surface, the largest earthquake of that time struck Prince william Sound. It was triggered by massive fracturing of the sinking edge of the Northeastern Pacific Ocean plate where it descends beneath the rocky slab carrying the North American Continent.
Photo modified courtesy of Tilling, Heliker, and Wright, 1987 and Hamilton, 1976. --Topinka, USGS/CVO 1999
The earthquake and the rupture in those rocks extended horizontally nearly 800 kilometers, roughly parallel to the Aleutian Trench. Measurements of the wave amplitudes put the magnitude of this quake at between 8.0 and 8.6 on the Richter Scale, making it one of the largest earthquakes ever recorded. Few, if any earthquakes of this magnitude have existed. Within minutes, thousands became homeless, and over 100 people lost their lives. Tsunamis raced across the Pacific Ocean to Antartica, British Columbia, California and Hawaii.