Fig. 4

Model for the alternate subduction-related explosive volcanic eruptions as a function of the LOD variability. The variation of the shear stress during LOD oscillation determines an increase or a decrease of the horizontal stresses acting on the crust (illustrated by Mohr’s circles). Along E-directed subduction zones, the volcanic arc is located in volumes undergoing contraction, since the subduction hinge is approaching the upper plate. The LOD increase determines a higher σ ₁, a lower hoop stress (σ _H) and a consequently larger differential stress favouring rupture. Along W-directed subduction zones, where the subduction hinge migrates away relative to the upper plate, the volcanic arc is rather erupting in the extensional back-arc setting. There, the LOD decrease rather generates a smaller σ ₃, a higher σ _H and a larger differential stress, favouring rupture