by Rasha Aridi/Smithsonianmag.com
Between 1976 and 2020, nearly 57,000 earthquakes rattled our planet. The bulk of them were shallow, and only a mere four percent occurred beyond 186 miles deep, which was thought to be the maximum depth for what scientists call “deep earthquakes,” reports Maya Wei-Haas for National Geographic.
Now, a team of researchers has zeroed in on what could be the deepest earthquake ever detected, shaking up scientists’ understanding of them. In 2015, a 7.9 magnitude earthquake struck beneath Japan’s Bonin Islands. One of the aftershocks occurred deeper than the original earthquake itself, at 467 miles. It’s so deep that it nears the layer of Earth known as the lower mantle, reports Andrei Ionescu for Earth.com.
“This is by far the best evidence for an earthquake in the lower mantle,” Douglas Wiens, a seismologist at Washington University in St. Louis who was not involved in the study, tells National Geographic.
The study, published in the journal Geophysical Research Letters, used measurements collected by the High Sensitivity Seismograph Network, a string of stations across Japan that record seismic data. They were able to trace the origin of the seismic waves produced by the 7.9 magnitude earthquake and its aftershocks, according to a press release.