Subduction age and stress state control on seismicity in the NW Pacific subducting plate

Abstract

Intermediate depth (70–300 km) and deep (> 300 km) earthquakes have always been puzzling Earth scientists: their occurrence is a paradox, since the ductile behavior of rocks and the high confining pressure with increasing depths would theoretically preclude brittle failure and frictional sliding. The mechanisms proposed to explain deep earthquakes, mainly depending on the subducting plate age and stress state, are generally expressed by single parameters, unsuitable to comprehensively account for differences among distinct subduction zones or within the same slab. We analyze the Kurile and Izu–Bonin intraslab seismicity and detail the Gutenberg–Richter b-value along the subducted planes, interpreting its variation in terms of stress state, analogously to what usually done for shallow earthquakes. We demonstrate that, despite the slabs different properties (e.g., lithospheric age, stress state, dehydration rate), in both cases deep earthquakes are restricted to depths characterized by equal age from subduction initiation and are driven by stress regimes affected by the persistence of the metastable olivine wedge.

Evaluation of the b Maps on the Faults of the Major (M > 7) South California Earthquakes

“…Some authors weight each earthquake based on the distance from the node. This method, first introduced by Tormann et al (2014), has been modified and applied to several regions of the world by many authors (see among the others Kamer and Hiemer (2015), Taroni et al (2021), García-Hernández et al (2021), and Pino et al (2022)). In all these cases, the most widely used approach is to grid the space into equal-sized cells and select the earthquakes according to certain rules (minimum number of events, maximum distance from the center of the cell, etc.).…”

“…(2021), and Pino et al. (2022)). In all these cases, the most widely used approach is to grid the space into equal‐sized cells and select the earthquakes according to certain rules (minimum number of events, maximum distance from the center of the cell, etc.).…”

Statistical Analysis of Mt. Vesuvius Earthquakes Highlights Pitfalls in Magnitude Estimation

“…The b parameter of the Gutenberg-Richter (GR) distribution [8] represents one of the most important parameters in the characterization of seismic occurrence because (i) it is crucial in the evaluation of the seismic hazard and (ii) it is inversely correlated to the stress state [9][10][11][12]. The spatial distribution of the b-value has been largely used to characterize stress regimes [13] and the spatial variations of the stress intensity in different seismogenic areas [14][15][16], including intermediate and deep seismic zones [17]. Several studies have also investigated the distribution of the b-value to individuate asperities on active faults [14,15,18], to characterize the complexity of the fault geometry [19], or to discriminate between distributed and on-fault seismicity [20].…”