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


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.

  • Phillip HOLLIS-WATTS

    How many nuclear reactors would be affected in the area of concern?
    Do they have suitably high walls for possible tsunamis? Are there contingency plans as yet for this possibility?

    • phu

      Those are all serious questions. It’s likely a panel of inquiry will be formed for each one, ignored, dissolved, and re-formed. All of this is likely to take at least three to four years and repeat itself… I would not wait for answers. You’ll find old age first.

  • Interesting findings that had me quizzing how would a major movement affect the Marianas just south of Tokyo.

  • I remember years ago writing to an eminent seismologist in Japan now sadly passed away. He was really keen on getting people in the Tokyo area to move to less quake zone areas. I am sure that the capital will survive, but when the next big one strikes wonders if all the precautions are up to standard. I remember that several buildings received approval but the ratio of materials was not to standard. Corruption and organized crime has meant short cuts were taken. Today government should be honest and transparent and rigously check structures. Also if possible a greater decentralisation is needed.