What causes earthquakes? The science behind why seismic events happen
Multiple notable earthquakes have struck the United States this year, including a powerful quake in California and a historic event on the East Coast earlier in 2024.
Strong earthquakes can lead to damage, tsunami warnings and more. People can also be injured or killed by damage caused by a quake.
Here's what to know about earthquake activity and what causes the phenomenon.
What causes earthquakes?
Earthquakes occur when the plates that make up the Earth's crust move around. These plates, called tectonic plates, can push against each other.
Earthquakes are most common along fault lines, which are fractures that allow the plates to move.
Earthquakes occur when two plates suddenly slip past each other, setting off seismic waves that cause the planet's surface to shake, according to the USGS.
What is an earthquake, scientifically speaking?
An earthquake is what happens when the seismic energy from plates slipping past each other rattles the planet's surface.
Those seismic waves are like ripples on a pond, the USGS said.
The earthquake will be strongest at its epicenter, the point on the surface directly above where the quake started, and the effects will be diminished as they spread further.
Where are earthquakes common?
Earthquakes are common on the West Coast, with multiple plate boundaries like the San Andreas fault making geologic activity more likely. They are rarer on the East Coast, but they do happen. Moderately damaging earthquakes strike between New York and Wilmington, Delaware, about twice a century, the USGS said, and smaller earthquakes are felt in the region roughly every two to three years.
On the West Coast, it can be possible to determine exactly which fault line a quake originated along, the USGS said, because of how well-studied some of those plate boundaries are. But on the East Coast, the nearest plate boundaries are in the center of the Atlantic Ocean, making it harder to study the area.
While East Coast earthquakes are less common than their counterparts on the West Coast, they tend to be felt over a wide area, the USGS said, as evidenced by a April 2024 quake centered outside New York City that rattled much of the East Coast. A 4.0 magnitude quake could be felt more than 60 miles from its epicenter, the agency said.
Will earthquakes happen more frequently?
In January, the USGS estimated that nearly 75% of the U.S. could experience a damaging earthquake in the next century. The prediction is based on research done by dozens of scientists and engineers using seismic studies, historical geological data and new information to identify nearly 500 additional fault lines that could produce damaging quakes.
It is possible that the central and northeastern Atlantic Coastal region could see more temblors, researchers said. Earthquakes are also likely in California and Alaska, which are historically seismically active regions.