The powerful earthquake that jolted the Tohoku region late Wednesday was likely an intraslab earthquake in which a tectonic plate under the sea ruptured internally, according to experts.
Tohoku University Prof. Shinji Toda said that although intraslab earthquakes occur deep underground, such temblors generate short-period seismic waves and can often produce strong shaking. The earthquake's epicenter was close to the coast, which resulted in strong jolts being felt widely in the Tohoku and Kanto regions.
Toda, an expert in seismology, added that the earthquake occurred in a location close to the epicenter of the powerful earthquake that struck off the Fukushima Prefecture coast in February 2021. That earthquake registered upper six on the Japanese seismic intensity scale of seven. Toda suggested the quakes might be linked.
According to Nagoya University Prof. Koshun Yamaoka, a seismology expert, the latest earthquake's epicenter was included in a region that includes the focal area of the March 2011 Great East Japan Earthquake and has been seismically active even after that disaster. Wednesday's temblor appeared to be a reverse fault type in which an upper block, above the fault plane, moves up and over a lower block it is pushing against.
University of Tokyo Prof. Emeritus Naoshi Hirata, a seismology expert, said, "After a big earthquake happens, quakes of similar strength could occur again. I urge people living in houses that are not earthquake-resistant to quickly evacuate to a safe place."
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