Abstract
The shape of a subducting slab varies as a function of trench motion. Two end-members of subduction modes are geodynamically possible: roll-back mode underneath neighboring plates and roll-over mode underneath the plate itself. Whereas most of major slabs seem to roll back while the Pacific plate shows a slab piling behavior down to ∼1,000 km depth under the Mariana trench, no clear evidence of slab roll-over in nature has been reported so far. Here we show a possible roll-over slab beneath the Caroline microplate, revealed from its three-dimensional seismic velocity structure derived by analyzing teleseismic reverberating SS phases. We suggest that slab roll-over is driven by at least two factors: 1) the overall buoyancy and fragility of the Caroline microplate at the surface, induced by a thin hot mantle plume that rises from depths ≥800 km; and 2) the pushing force of the Pacific plate acting on the trailing edge of the Caroline plate.
Highlights
Seismic tomographic studies have imaged various subduction patterns (e.g., Okino et al, 1989; Fukao and Obayashi, 2013; French and Romanowicz, 2015; Hosseini et al, 2020)
The dating of the CHT could be the trace of the Caroline plume from the core-mantle boundary (CMB), which might have been a source for the Caroline ridge, and probably the Sorol trough
Individual double-difference traveltime (DDTT) values show that SS phases arrive much faster than Preliminary Reference Earth Model (PREM) prediction and S phases arrive as predicted by PREM (Supplementary Figure S4A)
Summary
Seismic tomographic studies have imaged various subduction patterns (e.g., Okino et al, 1989; Fukao and Obayashi, 2013; French and Romanowicz, 2015; Hosseini et al, 2020). The Caroline plate has a complex and discussed geologic history, that includes tectonic rotations, protracted and recent subduction, former rift jumping and abortion, young spreading centers, plate boundaries of unknown geometry and kinematics, and hotspot and volcanic activity (Gaina and Muller, 2007) This microplate is roughly hexagonal (approximately 1,800 km × 1,000 km) and is trapped among three major converging plates (Figure 1): the Australian (south), Philippine (west and north-west), and Pacific (east and northeast) plates (Weissel and Anderson, 1978). The dating of the CHT could be the trace of the Caroline plume from the core-mantle boundary (CMB), which might have been a source for the Caroline ridge, and probably the Sorol trough
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