50th Anniversary of Largest Earthquake in US History

Anchorage, Alaska, 1964. At 5:30 PM on March 27th, Good Friday, the ground began to shake. Eyewitness Patrick Sanford’s father stopped his car to see what was wrong with his steering. Airman Patrick Hames thought the rumbling he heard was the thump of footsteps at shift change, while James Midlothian assumed it was a pilot revving his airplane engines; another airman suggested it was a bomb. Easter lilies began to fall off the shelves on top of Merry-Rae Brook and her fellow Girl Scouts, who were selling cookies in a grocery store. The cups in Patrick Keulan’s cupboards began to shake against each other, and a moment later the china hutch fell over.

It would not be a good day for dishes.

The quake’s epicenter was in Prince William Sound, east of Anchorage. All around the Sound, in Anchorage, at Elmendorf Air Force Base, in Seward and Kenai and a dozen other small settlements, cupboards disgorged their contents onto kitchen floors, parked cars crashed into each other, powerlines danced and refrigerators were toppled. The shaking lasted several minutes, a rare situation, as most earthquakes are of fairly short duration – about 30 to 40 seconds for a magnitude 6 quake. But this was no magnitude 6 – this was a magnitude 9.2, the second largest earthquake ever recorded and the largest in North America. The degree of shaking was so strong that the seismographs in the College, AK measuring station could not record the waves, leaving the seismogram blank until the earth finally calmed down and the needle, stuck on an unrecordable extreme, could be reset.

At Fort Richardson, Patrick Keulan’s mother thought the world was ending and refused to leave the house. Over the sound of breaking glass and masonry, the rumble of moving plates could be heard. Eyewitness Clark Jillson said the roar of the earthquake “sounded to me like I was standing next to a railroad track with a train roaring past.” The shaking continued violently, seeming to go on forever. Rocky Plotnick, another survivor, described it “like being on a small boat in confused and stormy seas.” Many people who lived through the quake described the trees swaying so violently they seemed to be “laying on the ground one minute and upright the next”. Witness Robert Williams said, “The ground in the front yard looked like water waves.” In Valdez, a babysitter had to throw her charges across a fissure that opened in the floor of the house she was working at, then jumped herself, falling and breaking a rib but making it out alive; the children’s father was swept away with the town’s docks by a massive mudslide triggered by the quake.

When it was over, the neighborhood of Turnagain had been swallowed by a 130-acre landslide, and the waterfronts of Valdez and Seward had collapsed into the sea. Around 130 to 140 people died as a result of the quake, but only about ten of those were killed thanks to the immediate damage of the earthquake itself; the vast majority died due to the tsunami waves produced by the quake and the resultant subsea landslides. These casualties included beachwalkers in California and Oregon as well as over a hundred Alaskans. The tsunami was recorded throughout the Pacific, as far south as New Guinea, and remains the second largest tsunami ever recorded – larger even than the 2004 Indonesian tsunami, though thankfully far less deadly. The wave at Valdez reached 67m, or almost 220 feet high.

In an age before cell phones, with the phone lines down, messages of “we’re okay” were relayed between family members over the local radio station. Because the water mains had burst, families had to melt snow for drinking water and to flush their toilets. With powerlines down and gas lines broken, cooking was done on barbecues or camp stoves. People whose homes were still safe took in those whose homes had been destroyed. Roads had turned into mazes of cracks and fissures and many bridges had collapsed, leaving people entirely cut off from civilization for several days. The National Guard was brought in to prevent looting, but there was no need; no one attempted to take such advantage of the tragedy.

Aftershocks continued for over a year after the quake, with eleven over magnitude 6.0 on the first day alone and another nine in the following weeks. The whole geography of the area had been reworked. Vertical displacements as a result of the quake ranged from two meters of subsidence to fifteen meters uplift (almost fifty feet), all of it instantaneous. The Pacific plate, in four minutes of rupture, moved about nine meters forward under North America. The normal rate of motion is 5-7 cm/yr, meaning the earthquake accommodated about 120 years’ worth of movement in a single brief event.

Large plate-boundary earthquakes such as this – specifically, at a subduction zone – tend to be of greater magnitude and depth than other earthquakes, and occur much less frequently that shallower quakes along local faults. The 1964 rupture was 25 kilometers deep and will probably not be repeated for 500 years or more. This is not unusual for a subduction zone. Nine out of the ten largest earthquakes in the last century were at subduction zones, including the Indonesian earthquake in 2004, the Japanese earthquake of 2011, and the largest earthquake ever recorded, which happened in Chile in 1960 and was of magnitude 9.5.

Today, the Turnagain Heights landslide area is a park. “Ghost forests”, standing dead trees drowned by subsidence caused by the earthquake, can still be seen around the area. For the many other seismically-active places along the Pacific coast of the US, this earthquake serves as a reminder never to discount the possibility of the “Big One”. It may not come today… but it will come, and when it does, people had best be ready.

On a lighter note, many of the witnesses of the Alaska quake were living and working on the military bases in the area. One Navy man recalled that many of his comrades were showering in preparation for a night on the town when the quake hit. All of them raced outside in a panic, many buck naked, falling over each other on the stairs. They emerged from the building only to find a group of screaming women – almost the only time he had ever seen a woman on the base.