Heat flow as a primary control factor on global earthquake magnitude distribution

The earthquake magnitude distribution, commonly described by the Gutenberg-Richter law, is governed by the b-value, a parameter that quantifies the relative frequency of large versus small earthquakes. Variations of the b-value have been attributed to different physical factors, such as tectonic setting, focal mechanism, lithology, fault geometry, and differential stress. Here we contribute to increase the understanding of the b-value variations analyzing the global correlation with the heat flux.

Our analysis reveals a specific trend: globally, we find a positive correlation between high b-values and high heat flux mostly driven by the peculiar seismicity at oceanic spreading ridges, independent of the focal mechanisms of seismic events. More interesting is the fact that, even removing from the analysis the seismicity at these spreading ridges, the significant correlation persists, independently from other local factors such as tectonic regime, or lithological composition.

These findings align with prior localized studies on thermally induced microfracturing and volcanic seismicity, where heat has been observed to influence fracture mechanics. Our results extend these observations to a global context, establishing heat flow as an important control on earthquake magnitude distribution.