The most powerful earthquakes can occur in places where classical theory suggests they are unlikely, and the cause lies in the orientation of tectonic stresses, which current models fail to consider. This was reported by specialists from the University of Tokyo, whose work was published in the journal Geophysical Research Letters.
According to Anderson’s theory of faulting, in zones where one plate subducts beneath another at a shallow angle, not enough energy should accumulate to generate strong tremors. Yet in practice, such areas often become the source of the most catastrophic events.
To understand the reason for this discrepancy, researchers analyzed the global earthquake catalog for 1976–2024. They focused primarily on the b-value—a parameter that indicates the ratio between small and large tremors. The lower this value, the higher the risk of a destructive event.
It was found that faults with shallow dips, where the plate descends almost horizontally, tend to have much lower b-values. This means they have a greater potential to produce a major earthquake.
The scientists concluded that the traditional model misses a crucial detail: the direction of the tectonic stress field. Calculations showed that, under certain stress orientations, even shallow faults can accumulate a critical amount of energy.
According to the authors, accounting for stress orientation could help more accurately identify areas with elevated seismic hazard. This could improve natural risk assessment and the operation of monitoring systems in the most vulnerable regions.
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