Correlation between seismic activity and tidal stress perturbations highlights growing instability within the brittle crust

Abstract

Faults become more and more responsive to stress perturbations as instability mounts. We utilize this property in order to identify the different phases of the seismic cycle. Our analysis provides new insights about the features of impending mainshocks, which are proposed to emerge from a large-scale crustal-weakening preparation process whose duration depends on their seismic moments, according to the power-law T $$\propto$$ ∝ M$$_{0}^{1/3}$$ 0 1 / 3 for M$$_{0}$$ 0 $$\le$$ ≤ 10$$^{19}$$ 19 N m. Moreover, further studies are performed about the impact of tidal stress perturbation on seismicity; in particular, the relationship between frequency-magnitude scaling and perturbations is discussed, showing that the sensitivity of earthquakes to solid Earth tides decreases as their magnitudes increase.

Variable seismic responsiveness to stress perturbations along the shallow section of subduction zones: The role of different slip modes and implications for the stability of fault segments

“…Tidal stress is calculated following the procedure described in Zaccagnino et al (2021). Starting from displacements induced by tidal potential W (r, θ, ϕ)…”

“…LFEs represent a peculiar class of seismic events featured by smaller slip rate and longer duration than regular earthquakes of equivalent magnitude, while non-volcanic tremors are weak events diffuse along subduction zones connected with reduced friction at slipping faults associated with fluid circulation (Beroza and Ide, 2011). In this respect, it may be interesting to evaluate how stress perturbations act on the system as silent and seismic events head fault dynamics, so that unstable or critical states may be highlighted (Zaccagnino et al, 2022a). A widely used approach consists in perturbing a system placed in an energy state H 0 and studying how it reacts to a small perturbation εH.…”

Earth’s gradients as the engine of plate tectonics and earthquakes

“…Once more, this effect highlights the critical component of seismic phenomena and their intrinsic non-linearity. Perturbation analysis also provided evidence that locked faults tend to become more and more sensitive to stress perturbations as they reach the breaking point [333]. The response of seismicity to perturbations also depends on the tectonic setting because of the different rheological profile, according to Eq.…”

“…C Histogram of energy nucleated by earthquakes with M L ≥ 1.0 (blue bars) and plot of the number of recorded seismic events (red line). After [333] as "large" if its magnitude is almost the maximum observed or possible to be nucleated within a fault system according to the concept of "soft cut-off" of the Gutenberg-Richter law introduced in [266]. However, the Gaussian-like roll-off introduces an additional degree of freedom in the frequency-size distribution, or, if the width of the filter is assumed on a priori grounds, such a choice cannot be rigorously justified and a more general framework should be invoked (e.g., [28]).…”

“…C Histogram of energy nucleated by earthquakes with M L ≥ 1.0 (blue bars) and plot of the number of recorded seismic events (red line). After[333]…”