The deepest earthquake ever, which occurred off Japan in 2015, reached into Earth's lower mantle, a staggering 467 miles (751 kilometers) below the Earth's surface.
Scientists have detected the deepest earthquake ever, a staggering 467 miles (751 kilometers) below the Earth's surface.
That depth puts the quake in the lower mantle, where seismologists expected earthquakes to be impossible. That's because, under extreme pressures, rocks are more likely to bend and deform than they are to break with a sudden release of energy.
But minerals don't always behave precisely as expected, said Pamela Burnley, a professor of geomaterials at the University of Nevada, Las Vegas, who was not involved in the research. Even at pressures where they should transform into different, less quake-prone states, they may linger in old configurations.
"Just because they ought to change doesn't mean they will," Burnley told. What the earthquake may reveal, then, is that the boundaries within Earth are fuzzier than they're often given credit for.