Authorities in Kumamoto Prefecture are urging strict vigilance against landslides as Typhoon No. 13 [1] approaches the region on Tuesday.
The warning follows a July 28 [1] earthquake that loosened ground stability in the area. This combination of seismic damage and incoming heavy rain creates a high-risk environment where slopes may fail more easily than they would under normal conditions.
Professor Tsuyoshi Sato of Tokyo City University said that slopes are currently in an unstable state. He said that because of this, there is a higher possibility of collapses occurring even with smaller amounts of rain compared to the period before the earthquake [1].
Local officials are particularly concerned about Ueki City and its surrounding areas [1]. The Meteorological Agency has already lowered the landslide-warning criteria for Ueki City to account for the precarious state of the terrain [1]. This adjustment means that warnings will be issued sooner and at lower rainfall levels to provide residents with more time to seek safety.
Residents are being advised to monitor weather reports closely and evacuate early if conditions deteriorate. The instability caused by the July 28 [1] quake means that traditional rainfall thresholds may no longer be reliable indicators of safety, making immediate response to official alerts critical.
Sato said, "(Because the slopes are) in an unstable state, it is thought that the possibility of collapsing even with a small amount of rain has increased compared to before the earthquake [1]."
“The July 28 earthquake has left slopes unstable and even light rain could trigger landslides.”
The lowering of warning thresholds indicates a shift from standard meteorological forecasting to a risk-mitigation strategy based on geological vulnerability. Because the seismic event of July 28 fundamentally altered the soil structure in Kumamoto, the region is now experiencing a 'compounded disaster' scenario where the secondary threat (landslides) is amplified by the primary event (earthquake), regardless of the typhoon's absolute intensity.
