Panel: Japan quake caused no large tsunami because of deep seismic center

The Yomiuri Shimbun

There were no large tsunami as a result of the quake that struck off Fukushima Prefecture late Saturday night due to the quake’s relatively deep seismic center, a government panel has announced.

The Earthquake Research Committee said at an extraordinary meeting on Sunday that the quake occurred inside the Pacific plate, and its seismic center was estimated at a depth of about 55 kilometers. As a result, the seabed was not drastically deformed and no large tsunami occurred.

The quake recorded a maximum of upper 6 on the Japanese earthquake intensity scale of 7. According to the committee, it took place where an oceanic plate slipped under the continental plate.

The epicenter of the quake was located about 110 kilometers southwest of the epicenter of the Great East Japan Earthquake, within the aftershock area of the 2011 disaster.

The committee said a tsunami about 20 centimeters high was recorded at Ishinomaki Port in Miyagi Prefecture, and tsunami of 10 centimeters at Sendai Port, in Soma, Fukushima Prefecture, and elsewhere. There were 54 aftershocks after the Saturday quake, three of which measured at least 3 on the Japanese seismic scale, as of 10 a.m. Monday.

The Meteorological Agency has issued a warning of earthquakes with a maximum seismic intensity of upper 6 for about a week. Naoshi Hirata, a professor emeritus at the University of Tokyo and a member of the panel, said: “A large tsunami might have occurred if the quake was larger in scale with a slightly shallower epicenter. It was barely avoided.”

“Even a 30-centimeter inundation from a tsunami can sweep an adult off their feet. People living in coastal areas should take precautions against tsunami,” Hirata said.

Strong tremors were observed over a wide area in the latest quake. According to Tohoku University Prof. Ryota Hino, a seismology expert, earthquakes of this type are less likely to cause tsunami because of deep epicenters, but they tend to be felt over a wider area than earthquakes with shallow epicenters.

Hino said such quakes also tend to cause quick “rattling” tremors that people easily can feel.

“The seismic intensity of the latest earthquake was strong partly because the epicenter was close to land,” he said.