Experts weighs in on powerful quake in Japan, urges vigilance against bigger ones

TOKYO - Several experts have weighed in on the powerful earthquake Monday night that triggered some tsunami along the Pacific coast in Japan's northeast, urging vigilance against future temblors.

Yoshihiro Hiramatsu, a professor at Kanazawa University and an expert on earthquake studies, said the latest quake may be attributed to a tectonic plate that had yet to break during the massive, magnitude-9.0 quake that hit the same region in 2011.

"Judging from the depth of the quake's origin and the angle of the fault, it is believed to have occurred at the border area where the ocean-side plate sinks beneath the land-side plate on which the Japanese archipelago lies," he said.

It could be described as having been caused by a tectonic plate that had yet to break because Monday's quake occurred north of the area where the Mar 11, 2011, quake originated, Hiramatsu said.

Noting that quakes of magnitude eight or greater have occurred in the region previously, including in 1968 off Tokachi, Hokkaido, the professor urged continued caution. 

He said the latest temblor may have shifted the balance in the ground, possibly laying the groundwork for a larger earthquake.

Takuya Nishimura, a professor at Kyoto University's Disaster Prevention Research Institute, said there is no question that the latest temblor was a so-called subduction zone earthquake, such as occurs at the boundary between two plates in the Pacific.

He said strong shaking was observed because the quake occurred near the land, even though it was far below the surface.

Hiroaki Takahashi, a professor at Hokkaido University on earthquake studies, also speculated that the movements of the tectonic plates caused the latest quake, urging caution against tsunami swells and strong shaking for the time being. - BERNAMA-KYODO