Friday Dec 02, 2022

Citizen Seismologists Track Haiti’s Earthquakes – The New York Times

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When a magnitude-7.0 earthquake hit Haiti in 2010 and killed an estimated 200,000 people, there was only one working seismometer in the country. The shaking quickly overwhelmed the seismometer, an education instrument installed at a high school, and it recorded little useful data.

Weeks passed before foreign seismic experts could travel to the disaster area, and then months passed before the portable seismometers they installed recorded enough of the fading aftershocks to shed light on the fault that had ruptured.

Last August, a magnitude-7.2 earthquake struck Haiti. Conventional seismometers installed after the 2010 quake were not functioning at the time. But several small, inexpensive instruments run by citizen scientists managed to capture the seismic waves, giving researchers a much quicker view of where the Earth had broken deep underground and demonstrating the value of enlisting the enthusiasm of curious nonexperts for science. (The earthquake’s death toll was about 2,200 people, much lower than the one in 2010, largely because the epicenter was in a more rural part of the country.)

“In 2021, we had that information in real time,” said Eric Calais, a geophysicist at the École Normale Supérieure in Paris who has studied the tectonics of the Caribbean for more than 30 years. “So that’s a big difference.”

Writing in an article published on Thursday in the journal Science, Dr. Calais and his colleagues described what the citizen science seismometers revealed about the August earthquake. About 40 miles of the same fault that caused the devastating 2010 earthquake ruptured, but farther to the west. The data also revealed some surprises, Dr. Calais said: At the eastern end of this segment, the fault was not vertical, where two tectonic plates are sliding past each other. Instead, the two plates were also being pushed together, with the northern one sliding on top of the southern one.

“If we hadn’t had the aftershock distribution, then we would not have been able to put in our models the proper full geometry,” Dr. Calais said. “Then our assessment of what went on would have been wrong.”

The Caribbean is sometimes a zone of overlooked seismic dangers with active volcanoes and earthquake faults. “The Caribbean is its own small-scale Ring of Fire,” said Susan E. Hough, a seismologist with the United States Geological Survey. “It’s like the Pacific Rim on a smaller scale.”

But the tectonic plates are crashing together at a slower pace, and major earthquakes occur less often. The second half of the 20th century was pretty quiet in the region. “People got kind of complacent about it,” Dr. Hough said. “The 2010 earthquake didn’t surprise any earthquake professionals in the world, but it surprised a lot of people that weren’t aware of the scientific results.”

Dr. Hough and Dr. Calais were two of the earthquake experts who traveled to Haiti in 2010. In the aftermath of the quake that year, international organizations provided financing to set up conventional seismometers, which cost tens of thousands of dollars each, in Haiti. When the magnitude-7.2 earthquake hit on Aug. 14, none of Haiti’s conventional seismometers were working, although a seismometer at the United States embassy was gathering data.

“It turns out to just be difficult, if not impossible, to run …….

Source: https://www.nytimes.com/2022/03/10/science/haiti-earthquake-seismometer.html

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