About the Nankai region

Scientists have identified the Nankai region, which includes 707 local jurisdictions in 29 prefectures, as having a 70-80% chance of experiencing a major earthquake and tsunami within the next 30 years.

What is Special Earthquake Warning Information for the Nankai Region?

If significant seismic activity in the Japan Trough (the subduction zone on the Pacific Ocean side of Japan) occurs, the Japan Meteorological Agency (JMA) may issue a short-term (5-10 day) warning or advisory for the region. Events that will trigger an alert:

The occurrence of a M8 would result in a warning
The occurrence of a M7 would result in an advisory
A “slow slip” event, indicating slip on the fault, would result in an advisory

Your local government should plan for receipt of a warning or advisory! We can help.

Why would one or more of the scenario events enhance concern?

Several of the recent earthquakes in Japan have been preceded by foreshocks or other seismic activity.

1. In 1854 there were two M8 earthquakes in the Nankai Region, 32 hours apart

2. In 1944 and 1946 there were two M8 Earthquakes two years apart

Left: Nankai trough setting of the 1944 and 1946 earthquakes.
Source: Fukushima, Y., Nishikawa, T. & Kano, Y. High probability of successive occurrence of Nankai megathrust earthquakes. Sci Rep 13, 63 (2023). https://doi.org/10.1038/s41598-022-26455-w

Right: Damage caused by the Showa Tonankai Earthquake in Owase Town, Kitamuro District, Mie Prefecture.
Source: https://www.wikidata.org/wiki/Q1049838#/media/File:昭和東南海地震による被害(1).jpg

3. Between March 9 and March 11, 2011, there were both slow slip events and foreshocks in the M6 and M7 ranges

Left: Japan's tectonic setting, illustrating the three subduction zones (Nankai Trough, Sagami Trough, and the Japan Trench) based on plate boundaries from Bird (2003); the rupture zone of the 2011 Tohoku event is shown along the Japan Trench.
Source: Apel, Trey, Williams, Chesley and Patricia Grossi. The M9.0 Tohoku, Japan Earthquake: Short Term Changes in Seismic Risk: RMS Special Report, Moody's RMS, 2012.

Right: Photo of March 2011 tsunami damage at a skilled nursing facility near Sendai.
Source: James D. Goltz, 2013 reconnaissance August, 2013; used with permission.