Publication of calculation results for the probability of large-scale earthquakes around the Nansei Islands Earthquake Research Commission

Regarding the probability of large-scale earthquakes occurring around the Nansei Islands, the government's Earthquake Research Commission has released a calculation result that a magnitude 8 class large earthquake may occur.

It is pointed out that sufficient caution is required, as there are cases where a huge tsunami occurred in the Maejima Islands of Okinawa Prefecture compared to the magnitude of the earthquake.

The government's Earthquake Research Committee reviewed the long-term evaluation of the scale and probability of earthquakes occurring in the trenches of the Nansei Islands and around Yonaguni Island in Okinawa for the first time in 18 years, and announced the results of the study.

According to it, the Kikaijima earthquake of magnitude 8.0 that occurred in the sea near Amami Oshima in Kagoshima prefecture in 1911 111 years ago is known around the Nansei Islands, but the epicenter is shallower than the previous evaluation from the latest research results. It is pointed out that it is considered to be.

On top of that, due to the uncertainty in the data, we conclude that the probability of an earthquake of magnitude 8 in this area within the next 30 years is "unknown", but that a huge earthquake of the same magnitude can occur anywhere. ..

In addition, the probability of a major earthquake with a magnitude of 7.0 to 7.5 within the next 30 years is "unknown" around the Nansei Islands, about 90% or more around Yonaguni Island, and a slightly deep place in the subducting plate off the northwest coast of the Nansei Islands. The earthquake that occurs in Japan is estimated to be about 60%.

In addition, in the Maejima Islands, it is thought that tsunamis of the same scale as the "Yaeyama Earthquake Tsunami" that occurred in 1771 and reached a maximum of 30 meters during the Edo period are repeatedly occurring, but the mechanism is unknown and the earthquake occurs. It is difficult to evaluate the activity.

It is pointed out that in such cases, a huge tsunami may occur compared to the magnitude of the earthquake.

Naoshi Hirata, chairman of the Earthquake Research Committee and a member of the National Research Institute for Earth Science and Disaster Prevention, said, "We reviewed our assumptions based on the idea that what actually happened in the past will happen in the future. We need to be very careful, remembering that there is a risk of an outbreak or a high tsunami. "