A regular review meeting was held to assess the possibility of a huge earthquake occurring in the Nankai Trough, and the opinion was summarized that "no particular changes have been observed."
A study group made up of experts analyzed data observed in and around the hypothetical source area of the Nankai Trough.
There has been no noticeable seismic activity since last month in areas that are assumed to be focal regions of large earthquakes.
Small-scale earthquakes called "deep low-frequency earthquakes," which frequently occur in and around the hypothetical focal region, were not observed.
On the other hand, in the central part of Shikoku, crustal movements different from the previous trends have been continuously observed since spring 2019.
This is thought to be caused by "long-term slow slip," in which the plate boundary slowly shifts on a yearly basis, and has been observed frequently so far.
For this reason, the study group has summarized the view that ``no particular changes have been observed that are considered to have relatively increased the possibility of a large-scale earthquake occurring compared to normal times.''
Tadashi Hirata, chairman of the study group and professor emeritus at the University of Tokyo, said, "Observation of data indicating that the Philippine Sea plate is subducting under Japan and that strain is accumulating continues. A large earthquake will occur in the Nankai Trough. It is not surprising that the situation continues, so I would like people to be prepared for an earthquake at any time."