(2)The earthquake near the coast of Amami Oshima Island (June 15, 1911, M 8.0)
This earthquake occurred near the plate boundary off the east coast of Amami Oshima. This was the largest earthquake in the Kyushu-Okinawa region. The seismic ground motion is estimated to have corresponded to a seismic intensity of 6 in JMA scale at Amami Oshima and Kikaijima Island, and 5 at Okinawa Island. The earthquake could be felt over an extremely wide area, and the seismic ground motion was estimated at a seismic intensity of 2 to 3 even in the Kinki region (Fig.9-13). This earthquake caused the small tsunami and could be felt over a wide area. Therefore, the consensus is that this earthquake occurred in a somewhat deep location inside a subducted plate. Some also maintain that, based on the location of the focal region, it was an interplate earthquake that occurred in a shallow area. On Kikaijima Island, one person died, nine were injured, and 401 of the 2,500 houses on the island were totally collapsed. A total of 11 houses were completely collapsed on Amami Oshima (Fig.9-14), and many houses were flooded. Five people also died on Tokunoshima Island. On the southern part of Okinawa Island, about 300 km from the hypocenter, stone walls collapsed in 598 locations, one person died, and 11 were injured. The aftershocks steadily decreased (Fig.9-15). A later earthquake in this area occurred on August 8 (M 6.2), but it is not known whether this occurred in the aftershocks area.