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.