MEXICO CITY — Late one night in September, Victor Cruz, a geophysicist at Mexico’s National Autonomous University, submitted an article to a scientific journal describing progress on a network of underwater seismic sensors to be deployed off Mexico’s Pacific coast.
The network, focusing on a seismically active area known as the Guerrero Gap, would track seafloor deformation and so-called silent slips, he wrote, with the goal of mitigating the human risks of earthquakes and tsunamis.
About an hour after Dr. Cruz sent his article, an 8.2 magnitude earthquake rocked the southern part of the country — the strongest to hit Mexico in more than a century. Two weeks later, a second quake killed hundreds around Mexico City.
As this country recovers, one of Latin America’s largest seismologic research projects is also feeling a jolt.
“We want to have a better understanding and go faster with our research,” said Josue Tago, a seismologist working to build the sensor network. “The research that we do can help save lives, and that’s a different kind of motivation.”
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All along Mexico’s west coast, the Cocos and North American tectonic plates meet, the former sliding under the latter. This so-called subduction zone yields periodic earthquakes, which release the energy building up as the plates push against each other.
The Guerrero Gap, just offshore, is of particular concern to scientists because of its proximity to Mexico City — about 200 miles to the southwest. The new network, which relies on GPS, pressure and seismic data, will analyze tectonic plate movement.
To do that, researchers will install sensors and take preliminary measurements in November. Then, over the next four years, a group of more than 50 scientists based in Japan and Mexico will gather data, create computational models of earthquakes and tsunamis, and generate maps of coastal areas near the gap at risk for the next big one.
But the two recent quakes have also highlighted differing scientific opinion about which parts of Mexico are now the most likely to yield the next earthquake. The zone along the coast of the state of Michoacan, which produced the giant quake of 1985? Somewhere southeast of the Guerrero Gap? The gap itself?
On one hand, one segment of the Guerrero Gap has not seen significant seismic activity in over a century, suggesting accumulated stress there could produce a large earthquake in the near future.
Recent quakes may have triggered a tectonic tremor there, but researchers do not know if any energy was released. “We’ll have to evaluate how much those processes could accelerate the movement,” Dr. Cruz said.
But the gap´s seismic silence is not totally convincing to all scientists. Some look at the 143-mile stretch and shrug, saying future quakes now appear even less likely to occur there, compared with other places along the coast.
”People get excited when earthquakes occur within or near a gap, but of course earthquakes occur elsewhere as well,” said David Jackson, a geophysics professor at the University of California, Los Angeles, who is not involved with the new network in Mexico.
”I’d follow the earthquakes, rather than the gaps,” he added. But “I’d rather have somebody instrument a gap than not instrument anything.”
Researchers trace the current focus on the Guerrero stretch of Mexico’s subduction zone to Japan’s 9.0 magnitude Tohoku quake and tsunami in 2011. It caught Japanese scientists by surprise, despite the nation’s highly sophisticated seismic network.
“That was an eye-opener for us,” said Vala Hjörleifsdóttir, a geophysicist at the National Autonomous University in Mexico City. “We think that we know what earthquakes could happen here. Is that it, or is there more?” she said.
Mexico, she noted, has not seen a large tsunami since 1932.
The Tohoku quake was preceded by a so-called slow-slip event, in which energy is released over a period of weeks or months. The Guerrero Gap has recorded some of the largest slow-slip events in the world, which intrigued Japanese seismologists.
Researchers at Kyoto University formally joined with scientists at Mexico´s National Autonomous University to study the area in 2013. The network they are starting to build will not only help detect earthquakes, but also offer data about plate tectonics and such slow-slip events.
If Mexico were a wealthier country, scientists say, a detection network might be extended, with seismometers blanketing the long stretch of ocean bottom between the Middle American trench — where the edge of the Cocos plate dives beneath the North American — and the shore.
But unlike other countries such as the United States, Japan, and New Zealand, which have used similar geophysical techniques to measure plate movements, Mexico is mostly dependent on the largess of others for its large-scale geophysics research.
About $6 million is dedicated to the current network, with about $2 million contributed by Mexico and the rest by Japan’s Science and Technology Research Partnership for Sustainable Development. Instruments supplied by Japan will be left in Mexico after the project is completed.
”There are so many priorities in Mexico that it’s difficult that a seismology geophysics project gets financing this big,” said Dr. Cruz of the new network.
A general lack of funding, combined with the general guesswork inherent in seismology, means scientists in Mexico must carefully pick locations to monitor. Because of the two recent quakes, resources are stretched even more thinly.
”The nature of the problem is that were never going to be right,” Dr. Hjörleifsdóttir said. “We’ve sort of been waiting for this big earthquake in Guerrero, but it’s not the only place.”
She compares the country’s monitoring efforts to those once focused on an area of the San Andreas fault in California, which produced earthquakes roughly every 20 years for about a century.
”In order to study the earthquakes, they instrumented it very well. And then once they put the instruments there, they just waited and waited, and it didn’t happen until like 35 years later,” Dr. Hjörleifsdóttir said.
Scientists can gather information about the earth’s movement that can contribute to disaster preparation, Dr. Cruz said. But they cannot predict earthquakes.
”Even though we, nor anyone else in the world, cannot know when an earthquake will happen,” he said, “we can generate knowledge that reduces the risk.”
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