What does the 2024 M 7.5 Noto Hanto, Japan, quake tell us about short-term forecasting and long-term hazard?

Earthquake Science Center Seminars

Shinji Toda, Tohoku University

The 1 Jan 2024 Noto Hanto earthquake launched a plethora of ills on the Noto Hanto population, taking 200 lives, and causing $25B in damage, only $5B of which was insured. These ills include a tsunami that arrived within a few minutes of the mainshock, as well as unexpectedly strong shaking throughout the Noto peninsula. In addition to direct shaking damage, the shaking triggered massive landslides in steep terrain, and caused extensive liquefaction in coastal marshes and estuaries. Coastal uplift of up to 4 m also lifted fishing harbors out of the water. Because the affected population locates nearly on top of the epicenter, neither the earthquake early warning nor the tsunami warning were effective. The earthquake was preceded by an extremely intense 3-year-long seismic swarm, and so efforts are under way to discern if the swarm triggered the earthquake, and if so, how. Whether swarms can trigger great quakes is a key question with which we must now grapple, as swarms are common in California, and elsewhere in Japan, as well. Sadly, the previously mapped offshore fault that ruptured was not used in the Japanese HERP hazard assessment, and so the Noto peninsula hazard had been greatly underestimated.