Sci-Friday: UAF Seismologist is on the hunt for the source of the great 1900 earthquake

Published: Apr. 16, 2021 at 5:14 PM AKDT
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FAIRBANKS, Alaska (KTVF) -Sometimes the best way to make predictions about the future is to look to the past. In 1900, Alaska experienced the largest earthquake on Earth recorded that year.

Seismologist Carl Tape set out to discover just how big this earthquake was, and if it could happen again. “There was a hint from some old records from 1900 in Kodiak that a large earthquake had occurred - and by large I mean it was talking about people getting thrown from beds, being felt in the western Aleutians, all the way east to Yakutat. o it was felt across a huge area. There’s been damage [reported], aftershocks for days and months.... so a big earthquake needs kind of a story. When did it happen? When did it start? Where was it?”

To answer these questions Tape tracked down many sources of historical information, from seismometer readings of the time to personal accounts from people who experienced the quake.

“It was a 1912 paper on some even larger earthquakes in Yakutat that happened in 1899. So there’d been two there, and these geologists went in and studied it. In that process they sent letters all over Alaska to ask about who had felt earthquakes in this time, and they found a lot of people had felt this 1900 earthquake. In their accounts basically they found that these stories about damage that had been caused, the wharf in Kodiak had been destroyed, chimneys were destroyed... there’d been enough reports like that where that’s pretty strong shaking,” said Tape.

Unusually, despite the extent of reported damage and the earthquake’s apparent magnitude, it did not generate a tsunami. “That’s an interesting question ‘cause in a lot of cases with big earthquakes it’s natural to generate a tsunami. We had records from federal ships that were in Kodiak, someone that was camping out, a biologist that was near sea level, and the lack of tsunami gives us a clue of where this occurred,” said Tape.

Based these and many other clues, Tape and his co-authors in a recent paper wrote that the earthquake’s epicenter was under the ocean floor, possibly 60 miles southeast of Kodiak, with a magnitude between 7.6 and 8.0.

According to Tape another earthquake like the 1900 event is going to happen again. “This 1900 earthquake is different from everything that we’ve seen. We don’t have a modern analogue, or a more recent recording to have an idea that this can happen in this part of Alaska. We sometimes need to look back in time at these historical events to get an idea of what’s active. Just because it’s quiet right now, does not mean that nothing’s ever gonna happen. So it’s very important in the vicinity of southern Alaska offshore, where we have earthquake faults that can create tsunamis, we need to understand these hazards both for people far away but also for Alaskans.”

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