As rescuers race to dig through the rubble left by Saturday’s 7.2-magnitude earthquake in Haiti, they will have to contend with aftershocks, landslides and potentially heavy wind and rain from a tropical storm triggering dangerous mudslides.
Already, several magnitude 5 or greater aftershocks have been recorded along with hundreds of landslides, by the U.S. Geological Survey.
“There's going to be aftershocks and USGS scientists have been working to get forecasts out,” said USGS seismologist Susan Hough, the agency’s event coordinator for the earthquake who also worked on the country’s 2010 earthquake that killed up to 300,000. “That's important for the response, to know what the odds are.”
Saturday’s quake occurred along the same fault system running through Hispaniola’s southern region, she said, and was likely set in motion by the 2010 event.
“You can think about dominoes falling, but you just don't know which is going to be the next one,” she said.
Named the Enriquillo-Plantain Garden fault zone, the zone forms the southern boundary of a smaller, micro plate between the massive North American and Caribbean plates.
As earthquakes occur, she said, they can nudge neighboring faults, although not always in strict sequence. A gap occurred between Saturday’s earthquake and the 2010 quake. She says a much smaller earthquake may have occurred in the 18th century that released some pressure and explains the gap.
“We can understand patterns after the fact, but what we want to do is know what's coming next,” she said.
Around the Earth, tectonic plates fit together like a puzzle. Just before 8:30 a.m. Saturday, the quake was recorded along the Enriquillo-Plantain Garden zone — about 78 miles west of Port-au-Prince and 60 miles west of the 2010 quake. It extended 6.2 miles deep and could be felt across Haiti and the Dominican Republic along with Jamaica, Cuba, and Puerto Rico, according to the USGS.
While earthquakes can’t be predicted, monitoring aftershocks can help predict activity in the days after a quake and guide rescue efforts. In 2010, that information was largely absent since the U.S. only monitors magnitude 4 quakes or greater.
“There was essentially no seismic monitoring in the country,” Hough said. “There was one educational seismometer that got blown off-scale. So there was no useful data.”
Getting teams into the heavily damaged country also delayed collecting the information, she said.
“I led one of them and it took a while,” she said.
Now that data is already flowing thanks to local scientists and an international team that established a monitoring network following the 2010 earthquake able to detect much smaller activity and improve the precision of forecasting hazards like landslides, she said.
“For a situation like this, we really want to know what part of the fault broke, what's the rate of aftershocks and what rate have we seen?” she said. “All of those forecasts are fine-tuned based on the observed aftershocks.”
The pandemic, and issues with security following the assassination of President Jovenel Moïse last month, is also complicating getting teams to the country. Those concerns, Hough said, will likely prevent a USGS team from going to Haiti.
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