News – ITHACA, NY- At a glacier near the South Pole, earth scientists have found evidence of a slow, slow slide triggered by strong, slow earthquakes many miles away, according to a Cornell University study published in Science Advances.
During an earthquake, a rapid slope occurs when energy builds up underground and is quickly released next to a fault. Blocks of ground quickly slide against each other.
However, at the Antarctic glacier known as the Whillans Ice Plain, earth scientists show that “slow slugs” span dozens of 7 large earthquakes. “We found that there is almost always a‘ slow slip ’before an earthquake,” said lead author Grace Barcheck, a research researcher in Earth and Atmospheric Sciences at Cornell University.
Barcheck said these slow precursors – occurring as far as 20 miles away from the center – are directly involved in the onset of the quake. “These slow ditches are very common,” she said, “and they migrate to where the rapid earthquake begins. ”
Observations before several major earthquakes generated by magnitudes 8 and 9 on transmission zone faults suggest a similar process could have occurred, according to Patrick Fulton, assistant professor and Sesquicentennial Croll Fellow in Department of Earth and Atmospheric Sciences.
Because these cracks are usually offshore and deep underwater, and because it is difficult to tell when or where a major earthquake will occur, it is usually difficult to see large earthquakes.
To overcome these challenges, the scientists placed GPS sensors over a frozen glacial fault at the Whillans Ice Plain, where magnitude 7 earthquakes occur nearly twice a day over a 60-ice area. -stream of the glacier.
Within two months of 2014, the group captured 75 earthquakes at the base of the Antarctic glacier. Data from GPS stations showed that 73 – or 96% – of the 75 earthquakes showed a period of slow movement beforehand.
The data from the GPS tracking stations and surface seismometers let the team identify how the slow slope triggers a rapid earthquake.
“Our group was amazed to see so many pre-runs,” said Barcheck.
“In some cases, we can actually see the migration of the earthquake to where the earthquake begins.”
“Before we looked at the data, I thought that if we saw predators before the earthquakes, they would be rare and in the same place as the epicenter of the earthquake,” she said. “Instead, we found a lot of slow precursors – starting miles from the high-level messengers and migrating over the flaw.”
In addition to Barcheck and Fulton, co-authors of the research, “Dominant Migration Earthquake Precursors on Ice Stream Fracture,” were Emily Brodsky, a professor, Department of Earth and Planning Sciences, University of California, Santa Cruz, who formerly a visiting professor at Cornell; Matt King, professor, Geography and Spatial Sciences, University of Tasmania, Hobart, Tasmania; Matthew Siegfried, Department of Geophysics, Colorado School of Mines, Golden, Colorado; and Slawek Tulaczyk, professor, Department of Earth and Planning Sciences, University of California, Santa Cruz.
Fieldwork and analysis for this research was supported by the National Science Foundation.