11 August 2024, Yo Fukushima

 

In May 2019, the Japanese Government introduced a new alert scheme against forthcoming great Nankai megathrust earthquakes (M8 or larger earthquakes that occur on the plate interface in the Nankai subduction zone). Under this scheme, the Japan Meteorological Agency alerts the public when the probability of a great Nankai megathrust earthquake increases to a level exceeding the norm. An earthquake of Mw 7.0 or larger around the megathrust and an abnormal slow slip on the megathrust can trigger these alerts.

There are two levels of alert: “warning” (higher level) and “advisory” (lower level). The terminology is from a White Paper on Disaster Management, published by the cabinet office of Japan. The one issued on 8 August 2024 was “advisory”, based on pre-determined criteria (that is, an earthquake of Mw 7.0 or larger and smaller than Mw 8.0 within the anticipated source region).

 

Here are some learning resources/papers written in English:

1)     White Paper on Disaster Management (2019). Cabinet Office of Japan, https://www.bousai.go.jp/en/documentation/white_paper/2019.html.
Chapter 3 describes the alert scheme.

2)     Goltz, J. D., Yamori, K., Nakayachi, K., Shiroshita, H., Sugiyama, T., & Matsubara, Y. (n.d.). Operational Earthquake Forecasting in Japan: A Study of Municipal Government Planning for an Earthquake Advisory or Warning in the Nankai Region. Seismological Research Letters. https://doi.org/10.1785/0220230304.
You can find the descriptions on an early attempt of “earthquake prediction” in Japan, and on the landscape of operational earthquake forecasting (OEF) in the world and in the Nankai region.

3)     Fukushima, Y., Nishikawa, T., & Kano, Y. (2023). High probability of successive occurrence of Nankai megathrust earthquakes. Scientific Reports, 13(1), 63, https://www.nature.com/articles/s41598-022-26455-w.
Table 1 of this paper gives the probability and probability gain for having a subsequent M8+ earthquake after an M8+ earthquake occurs, taking into account both the Nankai earthquake history and global statistics. Table S3 (Supplementary Material) gives the probability and probability gain for having a subsequent M8+ earthquake after an M7-level earthquake occurs based on the global statistics (which is applicable to the case that occurred on 8 August 2024).

4)     Hirano, K., Fukushima, Y., Maruya, H., Kido, M., & Sugiura, M. (2023). The Anticipated Nankai Trough Earthquake and Tsunami in Japan: Determinant Factors of Residents’ Pre-Event Evacuation Intentions. Journal of Disaster Research, 18(3), 233–245, https://www.fujipress.jp/jdr/dr/dsstr001800030233/.

5)     Maruya, H., Torayashiki, T., Sasaki, H., & Imamura, F. (2023). Proposal of a Recommended Correspondence Method for Companies and Organizations in Case of Partial Rupture of the Nankai Trough Earthquake. Journal of Disaster Research, 18(3), 217–232, https://www.fujipress.jp/jdr/dr/dsstr001800030217/.

6)     Sugiyama, T., & Yamori, K. (2022). Analysis of regional response and development of disaster prevention teaching materials for “Nankai Trough Earthquake Extra Information.” Journal of Integrated Disaster Risk Management, 12(1). https://doi.org/10.5595/001c.36180.

 

Return to Top Page of Yo Fukushima’s website