Explainer: What is an aftershock?

The earthquakes that rattled Italy on Wednesday were aftershocks of the deadly magnitude-6.2 temblor that struck the same region Aug. 24, U.S. Geological Survey (USGS) geophysicist John Bellini told Paste BN.

In the past two months, 32 aftershocks of magnitude-4.0 and greater have struck the area, he said.

So what exactly is an aftershock? And how does one differ from regular earthquakes?

“Aftershocks are just regular earthquakes, which happen in the neighborhood right after another larger earthquake,” John Vidale, a seismologist at the University of Washington in Seattle, told Paste BN after Japan quake in 2011.

The USGS says aftershocks can continue over a period of weeks, months or even years. In general, the larger the main earthquake, the larger and more numerous the aftershocks, and the longer they will continue.

There is, however, a difference between “aftershocks” and “triggered earthquakes,” Harley Benz of the USGS, said in 2011.

Benz said that while aftershocks occur on the same fault line as the original earthquake, the phenomena called “triggered earthquakes” occur on different fault lines — even though they’re related to the first quake.

The August quake in Italy killed nearly 300 people and destroyed the village of Amatrice. Wednesday’s temblors were felt in that town as well as L’Aquila, where a 2009 quake killed more than 300 people.

No injuries or serious damage were reported in Amatrice or L’Aquila in the wake of the latest quakes Wednesday.