Deformation of a weak subducted slab and variation of seismicity with depth

摘要: OCEANIC lithosphere is assumed to possess platelike properties whether it lying at the Earth's surface or descending deep into mantle; yet geometries of subducting slabs indicate significant deformation as they descend through mantle1–4, suggesting that lithospheric plates might be so weakened during subduction act not a rigid solid, but viscous fluid. Numerical and laboratory experiments have shown fluid 'slabs' can indeed take on realistic profiles5–7; however, has been clear 'weak' model slab dynamics account for earthquakes, which are usually ascribed 'strong' slab. Here we show, using numerical simulations evolution, weak in fact consistent with seismic observations. Assuming earthquakes occur rate proportional rate, reproduce observed variation depth seismicity focal mechanisms, cessation 670 km depth. Provided sinking material encounters resistance (here modelled viscosity jump km), pattern explained by any mechanism strain