With a total solar eclipse set to pass through the United States on Monday, it is easy to imagine a linkage between unusual events in the heavens and on Earth. But geoscientists were cautious about making such a connection.
Earthquakes happen along fault lines, or cracks between two blocks of rock on Earth’s crust. Tides stretch and squish the land on Earth just as they contribute to waves in the ocean, and those tidal forces grow as the sun, moon and Earth begin to align — a configuration that sometimes creates a solar eclipse.
One theory is that this may introduce additional stress along Earth’s fault lines.
“We do know that the relative position of the Earth and the moon and the sun does exert tidal forces,” said William Frank, a geophysicist at the Massachusetts Institute of Technology. “And we know that changes the stress that can be on a fault that can host an earthquake.”
But the results of several studies of the relationship between earthquakes and tides are inconclusive, according to Seth Stein, a geophysicist at Northwestern University. “If there’s any effect, it would be incredibly weak,” he said.
Earthquakes are driven most often by the motion between two tectonic plates making up Earth’s crust — either when two plates slide along each other in opposite directions, or when one slides under the other.
Both types of movements introduce strain at the junction, which often gets relieved by an earthquake.
But at the moment, it’s difficult to say that plate motion was responsible for the quake that shook the Northeast Friday morning.
“It’s not quite as obvious, because there is no tectonic plate boundary that is active,” Dr. Frank said.
Still, he added, fault lines from past activity are everywhere on Earth’s crust.
“Some of these faults can still be storing stress and be closure to failure,” he said. “And it can just require a little bit more to push it over the edge.”
