House displaced by compressional ridge formed at toe of L Street landslide Anchorage district. Cook Inlet region, Alaska. 1964. The 1964 Alaskan earthquake, also known as the Great Alaskan Earthquake, the Portage Earthquake and the Good Friday Earthquake, was a megathrust earthquake that began at 5:36 P.M. AST on Good Friday, March 27, 1964. Lasting nearly four minutes, it was the most powerful recorded earthquake in US and North American history, and the second most powerful ever measured by seismograph. This shock generated a tsunami that devastated many towns along the Gulf of Alaska, and left serious damage at Alberni and Port Alberni, Canada, along the West Coast of the United States (15 killed), and in Hawaii. The maximum wave height recorded was 220 feet at Valdez Inlet. It had a magnitude of 9.2, at the time making it the second largest earthquake in recorded history.