On September 7, 2017, a magnitude 8.2 earthquake struck southern Mexico, killing dozens and injuring hundreds. While earthquakes are common enough in the region, this powerful event wasn’t any run-of-the-mill tremor.

That’s because part of the roughly 37-mile-thick tectonic plate responsible for the quake completely split apart, as revealed by a new study in Nature Geoscience. This event took place in a matter of tens of seconds, and it coincided with a gargantuan release of energy.

“If you think of it as a huge slab of glass, this rupture made a big, gaping crack,” says lead author Diego Melgar, an assistant professor of earthquake seismology at the University of Oregon. “All indications are that it has broken through