Three-dimensional visualization of a near-vertical slab tear beneath the southern Mariana arc

Abstract

The use of a three-dimensional ray-tracing inversion algorithm has greatly enhanced the resolution of gradients and strong variations in wave speeds to create improved P wave tomographic images of the Mariana arc region. The images obtained from the Mariana arc region show relatively low amplitudes of heterogeneity due to the limited number of seismic stations in the area. Despite these limitations, detailed interpretations of the three-dimensional geometry and morphology of the Pacific Plate subducting beneath the Philippine Sea Plate have provided a three-dimensional model of the steep dip of the Pacific plate and the curvature of the slab beneath the Mariana arc in unprecedented detail. The new P wave tomography and seismicity depict a previously unidentified E-W trending near-vertical tear in the subducting plate at the southern end of the Mariana arc that divides the arc into two distinct segments: a steeply dipping curved slab penetrating the lower mantle and a short (∼250 km depth) slab along the Challenger Deep segment of the arc. The slab tear is likely to be the result of the need to accommodate the reduced volume the slab must occupy as it is subducted beneath the Philippine Sea plate along a curved arc. Show more