Global seismic energy scaling relationships based on the type of faulting

Abstract. We derived scaling relationships for different seismic energy metrics for earthquakes with M_W > 6.0 from 1990 to 2022. The seismic energy estimations were derived with two methodologies, the first based on the velocity flux integration and the second based on finite-fault models. In the first case, we analyzed 3331 reported seismic energies derived by integrating far-field waveforms. In the latter methodology, we used the total moment rate functions and the approximation of the overdamped dynamics to quantify seismic energy from 231 finite-fault models (E_mrt, and E_O, E_U, respectively). Both methodologies provide compatible energy estimates. The radiated seismic energies estimated from the slip models and integration of velocity records are also compared for different focal mechanisms by deriving converting scaling relations among the different energy types. Additionally, the behavior of radiated seismic energy (E_R), energy-to-moment ratio (E_R/M₀), and apparent stress (τ_α) for different rupture types at a global scale is examined by considering depth variations of mechanical properties, such as seismic velocities and rock densities, and rigidities. For this purpose, we used a 1-D global velocity model. In agreement with previous studies, our results exhibit a robust variation of τα with the focal mechanism. These parameters are, on average largest for strike-slip earthquakes, followed by normal-faulting events, with the lowest values for reverse earthquakes for hypocentral depths < 180 km. On the contrary, at depths in the range of 180–240 km, τ_α for reverse earthquakes is higher than for normal-faulting events. Regarding the behavior of apparent stress with depth, our results agree with the existence of a bimodal distribution with two depth intervals where the apparent stress is maximum for normal-faulting earthquakes. Finite-fault energy estimations also support focal mechanism dependence of apparent stress, but only for shallow earthquakes (Z < 30 km). The population of slip distributions used was too small to conclude that finite-fault energy estimations support the dependence of average apparent stress on rupture type at different depth intervals.