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.
Since last month, there has been no noticeable seismic activity in the hypothetical focal region of a large earthquake.
On the other hand, in and around the hypothetical focal region, a small earthquake called a "deep low-frequency earthquake" was observed in western Shikoku from 14th to 19th last month.
Along with this, slight crustal movements were observed with multiple "strain gauges" in the surrounding area, and it is believed that the cause is "short-term slow slip" where the plate boundary in the hypothetical focal region slowly shifts at a deep location.
In addition, in central Shikoku, crustal movements different from the trends up to that time have been continuously observed since around the spring of 2019, and it is thought to be caused by "long-term slow slip," in which the plate boundary slowly shifts on an annual basis. increase.
Since such phenomena have been observed many times in the past, the investigative committee said, ``We have not observed any particular change that would indicate that the possibility of a large-scale earthquake occurring has risen relative to normal.'' I have summarized my views.
Tadashi Hirata, chairman of the study group and professor emeritus at the University of Tokyo, said, "Observations of data showing that the Philippine Sea plate is subducting beneath Japan and accumulating force continue. Since the Showa Tonankai earthquake, Nearly 80 years later, the fact that a large earthquake could occur in the Nankai Trough has not changed, so I want people to be prepared for an earthquake at any time."