Spatial distribution of the contemporary stress field in the Kurile Wadati-Benioff zone by inversion of earthquake focal mechanisms

The results obtained indicate that the main geodynamic forces that drive the presently active processes at different depths along the Kurile Wadati-Benioff zone are the slab pull and ridge push at shallow depths, unbending of the slab at intermediate depths causing the observed two-planar stress pattern, and the mantle resistance in the central and northern deep-seated slab segments. The stress inversion results indicate also additional forces that participate in the contemporary dynamics within several WBZ subvolumes: lateral tension that modifies the σ3 orientation from slab-parallel into strike-aligned, trending NNE and NE in the lower plane of segment K1-2, in the intermediate-depth subvolume beneath Iturup island, and in the deep subvolume V2; forces modifying the orientation of σ1 within the subvolumes V1, V3 and V5 from slab-parallel into strike-aligned, trending SW, W and SW, respectively. The origin of these forces remains unsolved thus posing open questions for further investigations into the dynamics of the Kurile Wadati-Benioff zone.