World news – Slow-motion precursors give earthquakes their quick slip

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February 16, 2021

by Blaine Friedlander, Cornell University

On a glacier near the South Pole, earth scientists have found evidence of a low-level, slow-motion bug that causes powerful, rapid-slip earthquakes many miles away. This is evident from research by Cornell University published in Science Advances.

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During an earthquake, a rapid slip occurs when energy builds up underground and is quickly released in the event of a failure. Earth blocks slide quickly against each other.

However, on an Antarctic glacier called Whillans Ice Plain, earth scientists show that « slow slip » precede dozen of magnitude 7 earthquakes. « We have found that there is almost always a preliminary ‘slow slip’ before an earthquake, » said lead author Grace Barcheck, an earth and atmospheric research fellow at Cornell University.

Barcheck said that slow Slip precursors – which occur up to 20 miles from the epicenter – are directly involved in the start of the earthquake. « These slow slip-ups are remarkably common, » she said, « and they migrate to where the rapid earthquake slip begins. » Observations prior to several large tsunami-causing 8- and 9-magnitude earthquakes at subduction zone faults suggest that a A similar process could have taken place, said Patrick Fulton, assistant professor and Croll Sesquicentennial Fellow in the Department of Earth and Atmospheric Sciences.

Since these errors mostly occur offshore and deep underwater, and it’s difficult to know when or where to get one Large earthquakes will occur, the onset of large earthquakes is generally difficult to observe.

To address these challenges, scientists placed GPS sensors over an icy glacial fault in the Whillans Ice Plain, where magnitude 7 earthquakes almost twice a day occur on a 60 mile wide area of ​​the glacier.

In two months in 2014, the group experienced 75 earthquakes captured at the bottom of the Antarctic glacier. Data from GPS stations showed that 73 – or 96% – of the 75 earthquakes exhibited a preliminary slow-motion period.

Using the data from the GPS tracking stations and surface seismometers, the team was able to determine how slow preliminary slip was fast earthquake slip .

« In some cases, we can actually see the precursor migrating to where the earthquake begins. »

« Before we got into the data, I thought if we would see precursors before the earthquake , these would be rare and in the same location as the earthquake epicenter, « she said. « Instead, we found many slow-slip precursors – from epicentres to migration across the fault. »

Fieldwork and analysis for this research were supported by the National Science Foundation.

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Related titles :
Slow motion precursors give earthquakes the quick slip
Slow motion precursors give earthquakes a quick slip

Ref: https://phys.org

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