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 conspicuous seismic activity since last month in the hypothetical focal region of a large earthquake.
On the other hand, small-scale earthquakes called "deep low-frequency earthquakes" occurred in and around the hypothetical focal region, in
western Shikoku from the 8th to the 14th of last
month, in central Shikoku from the 23rd to the 30th of last month, and
in eastern Shikoku on the 15th of last month.
Each was observed
from the 20th to the 20th .
Along with this, slight crustal movements were observed with multiple "strain gauges" in the surrounding area, and it seems that the cause is "short-term slow slip" where the plate boundary in the hypothetical focal region slowly shifts at a deep place.
Since deep low-frequency earthquakes and short-term slow slips have been frequently observed in and around the hypothetical focal region, the investigative committee said, ``The possibility of a large-scale earthquake occurring is relatively high compared to normal times. It is thought that there was no particular change observed.”
Naoshi Hirata, chairman of the study group and professor emeritus at the University of Tokyo, said, "At the plate boundary of the Nankai Trough, seismic activity was relatively quiet in August, but the subduction of the Philippine Sea plate did not stop. The state of preparations for the next earthquake continues.It will not be surprising if a huge earthquake occurs at any time, so I would like you to continue to make sufficient preparations and prepare for the occurrence of an earthquake.” I called.