Later Tuesday, state seismologist Michael West heard a text alert. His phone alerted him to a major earthquake under the ocean, just south of the Alaska Peninsula, about 60 miles southeast of the village of Sand Point.
His first thought was that this – the largest earthquake on the planet to date in 2020 – would cause a devastating tsunami. His second thought was that a long-term earthquake mystery has just been solved.
To the relief of West, the magnitude 7.8 earthquake that occurred at 10:12 a.m. Alaska time did not cause a devastating tsunami. Reports of 6-inch waves at the edge of Sand Point were one of the highest recorded for the event.
West and his colleagues at the University of Alaska Fairbanks Geophysical Institute were still awake in data a day after the incident. But he was soon shown a scientific article written by the first Alaska seismologist, John Davies, in 1981.
All major recent earthquakes in the Aleutian Subduction Zone, including the magnitude 7.8 in the “Shumagin Gap” that occurred on July 21, 2020. (Graph with courtesy Alaska Earthquake Center)
In it, Davies and his colleagues proposed a “seismic hole” just south of Sand Point. There, she wrote, was an arch from one of the great subduction zones of the world that had not broken in a long time. It was often thanks to.
Davies made his prediction after field campaigns in the 1970s, in which he and his colleagues installed seismometers at Popof Island, on which the village of Sand Point (population 1,140 population) sits.
“From 1938 to 1965, almost the entire portion of Alaska’s subduction area broke,” West said. “There were only two places that did not ripen – one in the Yakutat area and another in the Shumagin Islands (where the earthquake occurred on July 21).
“Here, you have this 1981 paper that says you have ruptured everything except these sections, and that is where you should expect the next major earthquake.”
Subduction zone earthquakes are the largest and most devastating on Earth, West said, citing Good Friday 1964 and Tohoko earthquakes as examples. He described the Aleutian Subduction Zone, which is responsible for the existence of the Aleutian Islands, as follows:
“The Pacific Plate feeds a few inches northwest each year into the stronger North American plate,” he said. “This forces the Pacific Plate to drift below Alaska. Major earthquakes occur at the border where these two plates rub together. ”
John Davies, who wrote the paper predicting an earthquake like the one that occurred Tuesday night, was elected to the Alaska State Legislature in 1993. He then had to resign from his position at the Geophysical Institute, where, like West, the state was seismologist.
Davies’ doctoral dissertation, conducted in Skwentna, Alaska, helped prove the latest theory of plate tectonics, in which scientists such as his mentor David Stone claimed that the earth’s crust is made up of colossal blocks that slide into each other. Davies showed that the Pacific Plate did indeed dive deep beneath Anchorage, reaching almost as far as Denali.
After turning to politics, Davis never returned to seismology.
The day after the 2020 earthquake, he and his wife, Linda Schandelmeier, made kimchi from Napa cabbage that they harvested from their garden in Fairbanks.
Telephone reached Davies saying he was pleased to hear that his research from decades ago was suddenly relevant.
“That would be really gratifying if this turned out to be true,” Davies said.
West said the shadow of aftershocks of the earthquake was enough for him to believe that a significant portion of the Shumagin Gap was broken, and was perhaps not just a peculiar section that slipped silently without major earthquakes.
Davies, who as a state seismologist had a duty to find the areas with the greatest risk of earthquake and advise on building codes and warn of tsunami dangers, said that major earthquakes remind him somewhat of the present times.
“Earthquakes are like viruses – the really big ones come with it once in a lifetime, if at all,” he said. ‘We have these dangers that occur with such a long time between them. It’s hard to get people to pay attention. ”
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