Excess pore pressures within subducting sediments: Does the proportion of accreted versus subducted sediments matter?

摘要

Although previous numerical modeling studies have examined pore pressures in both accretionary and non-accretionary subduction zones, they have not addressed the question of whether the proportion of accreted versus subducted sediments significantly affects pore pressures. This modeling study used consistent parameters to compare excess pore pressures directly below the decollement for varying proportions of accreted sediment. Within the initial 5 to 12 kilometers arcward of the deformation front, subduction zones with lesser accretion thickness show lower simulated excess pore pressures than those with greater accretion thickness due to the ease of fluid escape when overlying wedge sediments are thin. However, at greater distances arcward of the deformation front, the magnitude of excess pore pressures significantly increases and the excess pore pressures peak further arcward as the proportion of underthrust sediments increases. This difference suggests that the proportion of accreted versus subducted sediment could potentially affect seismogenesis.