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May 5, 2013

Active seabed faults spanning 100 km found off Izu Peninsula: study

Kyodo

http://www.japantimes.co.jp/news/2013/05/05/national/active-seabed-faults-spanning-100-km-found-off-izu-peninsula-study/#.UYYL_EpsFEs

Active faults stretching over 100 km in total have been identified near the coast of the Izu Peninsula, Shizuoka Prefecture, and could generate a major quake affecting areas from Tokyo to the major industrial hub around Nagoya, a new study has shown.

The faults mostly lie in the Pacific seabed southeast of the peninsula, and the nearest one is only 2 km from the coast, according to the recent survey conducted by a team of researchers.

If all of the faults were to move at once, they could trigger an earthquake with a magnitude of 8.0 or higher whose effects would be felt over a wide area from Tokyo to the north and Aichi Prefecture to the south, the researchers said.

Geologists have long suspected that an active fault lies off the eastern coast of the Izu Peninsula.

After studying ocean floor topographical and other data provided by the coast guard, the researchers concluded that bulges in the seabed around the peninsula may have resulted from past movements of these faults.

The faults can roughly be grouped in five blocks and a movement in a single block could generate a magnitude 7.0 temblor. Areas around the peninsula are highly prone to quakes, with magnitude 5.0 or more powerful tremors repeatedly rocking the area, the researchers said.

The team that conducted the study included researchers from Kanagawa Prefecture’s Hot Springs Research Institute, which carries out geological surveys and monitors seismic activity.

Researchers find active seabed faults near central Japan coast

http://mainichi.jp/english/english/newsselect/news/20130505p2g00m0dm004000c.html

TOKYO (Kyodo) -- Researchers have found active faults stretching over 100 kilometers in total near the coast of a central Japan peninsula which could cause a powerful quake affecting Tokyo and a major industrial region centering on Nagoya.

The faults mostly lie in the Pacific seabed southeast of the Izu Peninsula in Shizuoka Prefecture and the nearest one is only about 2 km from the coast, according to their recent study.

The faults could cause a quake with a magnitude of 8 or stronger if they all move at once, the researchers said.

A research team concluded after studying the government's ocean floor topography and other data that bulges in the seabed around the peninsula resulted from fault movements.

The faults can roughly be grouped in five blocks and a movement in a single block can cause a powerful temblor with a magnitude of around 7, they said.

Areas around the peninsula are prone to quakes, with those with a magnitude of 5 or larger occurring repeatedly.

Researchers have long suspected an active fault lies off the eastern coast of the Izu Peninsula.

The researchers taking part in the study included those from the Hot Springs Research Institute of Kanagawa Prefecture, an organization conducting geological surveys and monitoring seismic activities.