A major earthquake struck Panama on Friday afternoon, but how many people have been affected remains unclear.
The quake struck at 12:56 P.M. local time and was initially measured as an 8.0 magnitude by the U.S. Geological Survey, but that was later downgraded slightly to a 7.7. The quake struck around nine miles (14 kilometers) southwest of Pitaloza Arriba, a small village in Panama’s Herrera Province. Around 4.6 million people experienced moderate to severe shaking, according to the USGS, and potentially strong aftershocks could follow.
On social media, Panamanian President José Raúl Mulino said he had given instructions to mobilize personnel, resources and aid to the area.
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No statistics on injuries or deaths have yet been released. The affected area has a relatively low population density.
While the U.S. National Oceanic and Atmospheric Administration’s Tsunami Warning System had initially warned that the quake could pose a tsunami threat in Costa Rica, El Salvador, Peru, Mexico, Guatemala, Nicaragua, Colombia and Ecuador as well as Panama, as of Friday afternoon the alert was no longer in effect.
The threat of tsunami has likely largely receded, says USGS seismologist Susan Hough, as the quake occurred on land and happened at a relatively shallow depth.
“Because this was on land and shallow, you’re not on the seafloor, so it didn’t move the seafloor underneath the water column, and that’s what you need to generate a tsunami,” she says.
Shallow earthquakes do lead to more shaking being felt at the surface, though. USGS modeling put the likely casualties in the range of dozens to hundreds of fatalities and damages in the hundreds of millions dollars.
The U.S. embassy in Panama did warn U.S. citizens in the area to avoid damaged structures, as well as the coast, and to monitor local emergency broadcasts for updates.
Panama is located near the intersection of several major tectonic plates. To the south are the Cocos and Nazca plates, with the Caribbean plate to the north and the South American plate to the east.
“It was a shallow lateral fault, what we call strike-slip, so similar to the San Andreas,” Hough says.
While the meeting place of tectonic plates can lead to the formation of subduction zones, areas where the denser plate is forced underneath the light plate into Earth’s mantle, which can lead to powerful earthquakes as pressure builds, Hough said the subduction zones near Panama don’t meet, which is why the country usually experiences less powerful quakes.
“There’s a complicated zone of faulting that’s at that juncture, and so this earthquake was on one of those faults,” she says. “It was quite large compared to other earthquakes that have been seen in that area.”
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