A regular study group was held to evaluate the possibility of a large earthquake in the Nankai Trough, and summarized the view that "no particular changes have been observed."
A study group made up of experts analyzed the data observed in and around the hypocenter area of the Nankai Trough.
In the area corresponding to the hypocenter of a huge earthquake, a magnitude 5.0 earthquake occurred in Hyuga-nada on the 2nd of last month, and tremors with a seismic intensity of 3 were observed in Miyazaki and Kagoshima prefectures.
This earthquake occurred at the boundary between the Philippine Sea plate subducting from the sea side and the plate on the land side, and earthquakes of magnitude 3 occurred one after another around it, but due to the scale of the earthquake, between the plates. It is considered that there is no particular change in the sticking state of.
In the hypocenter area and its surroundings, small-scale earthquakes called "deep low-frequency earthquakes" were observed from April 30 to 11 in eastern Shikoku and from 18 to 31 in the northern and central parts of the Kii Peninsula. It means that it was done.
Along with this, slight crustal movements were observed by multiple "strain meters" in the vicinity, and it is thought that the cause is "short-term slow slip" that slowly shifts at the deep boundary of the plate in the hypocenter area.
Deep low-frequency earthquakes and short-term slow slips are frequently observed in and around the hypocenter area, and the study group said, "The possibility of large-scale earthquakes is relatively high compared to normal times. No particular changes were observed that were thought to have occurred. "
Professor Emeritus Naoshi Hirata of the University of Tokyo, the chairman of the study group, said, "Although no unusual phenomenon has been observed to indicate that a large earthquake will occur, the Philippine Sea Plate continues to exert force on the Japanese archipelago in the Nankai Trough. Therefore, there is no change in the recognition that a huge earthquake will occur with an extremely high probability. Even in normal times, various preparations are being made for the next earthquake, so be prepared for an earthquake at any time. I want you to proceed. "