Abstract
The geometries of trenches vary worldwide due to continuous plate boundary reorganization. When two trenches intersect to generate a corner, a subduction cusp is formed. Although subduction cusps are frequently observed throughout historical plate movement reconstructions, few studies have been conducted to explore the controlling factors of trench migration and slab morphology along subduction cusps. Here, we use a 3-D dynamic subduction model to explore the influence of the overriding plate strength, initial slab-pull force, and initial cusp angle on the evolution of subduction cusps. Our numerical model results suggest the following: 1) subduction cusps have a tendency to become smooth and disappear during the subduction process; 2) the slab dip angle is smallest in the diagonal direction of the subduction cusp, and a larger cuspate corner angle leads to a larger slab dip angle; 3) the asymmetric distribution of the overriding plate strength and initial slab-pull force determine the asymmetric evolutionary pathway of subduction cusps. Our results provide new insights for reconstructing the evolution of subduction cusps from seismological and geological observations.
Highlights
During the evolution of plate tectonics, trenches located at the junction of subducting and overriding plates can develop various kinds of geometries (Schellart et al, 2007; Müller et al, 2016)
We explore the evolution of subduction cusps using a 3-D dynamic subduction model
The cuspate corner angle at the Kurile Islands was approximately 90° at 40 Ma and it became increasingly larger during the subduction of the Pacific plate (Figures 1A–C), which is consistent with our model results (Figures 5B–D)
Summary
During the evolution of plate tectonics, trenches located at the junction of subducting and overriding plates can develop various kinds of geometries (Schellart et al, 2007; Müller et al, 2016). When two trenches intersect with each other to form a corner, we define it as a subduction cusp. At 40 Ma, the trenches along the Kurile Islands and northeast Japan intersected and formed a subduction cusp (Figure 1A) (Vaes et al, 2019). At 35 Ma, the Pacific plate subducted beneath the Eurasian and Philippine Sea plates, and the trenches along the Eastern Japan and Izu-Bonin arc were generally perpendicular to each other, forming a subduction cusp (Figure 1D) (Hall, 2002; Ma et al, 2019). It is possible that the cusps linking the Kurile Islands and northeast Japan trenches and the Izu-Bonin arc and East Japan trenches (Figure 1) were generated by the subduction of oceanic plateaus that have since been entirely consumed (Rosenbaum and Mo, 2011)
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