New research reveals that megathrust earthquakes change seismic risk for decades: Insurance implications for Japan, Chile and Cascadia
In a study published in Nature Geoscience in June, Temblor scientists discovered that megathrust (M≥9) earthquakes fundamentally alter seismic hazard in the ensuing decades to centuries.
Shinji Toda and Ross Stein showed that following historic megathrust quakes, aftershocks ceased on the ruptured surfaces within several years of the mainshocks, and they argue that seismicity will remain shut down in this ‘core’ for more than 300 years. In contrast, abundant aftershocks persist in a ‘corona’ around the mainshock for up to half a century, raising the coastal hazard. Insurance markets in Japan (M 9.0 in 2011), Chile (M 8.8 in 2010) and Cascadia (M~9 in 1700), are all affected. Each has a current seismicity hole brought about by the recent megathrust quakes, and in Japan and Chile, the coastal hazard is still much higher than before the mainshock struck. Traditional earthquake risk models do not account for such dynamic hazard changes.
Corona aftershocks can be highly destructive if they strike close to shore. This was apparent in March of 2022, when a magnitude-7.3 aftershock shook harder and caused more damage in nearby Fukushima, Japan, than its 2011 Tohoku mainshock, which was 350 times larger.
“Any risk model that does not take these effects into account cannot gauge the true hazard,” says Stein, Temblor’s CEO and co-author of the study. Temblor’s Realtime Risk model captures this phenomenon, enabling short-term and renewal-year forecasts.
Stein will talk about the study and its impact on the catastrophe insurance market
Temblor will be hosting a livestreamed webinar
Presented by Ross Stein, Ph.D.
Monday, July 11 at
8 am Los Angeles
11 am New York
4 pm London
5 pm Zurich