Investigating Fluid Release and Aftershock Activity in Subduction Zones: A Numerical Study Using MDOODZ and Perple_X

Fluid plays a pivotal role in the dynamics of subduction zones and earthquake activity. Recent observations have revealed that some megathrust earthquakes (Mw > 6.8) are followed by abundant aftershocks (Mw > 4), while others of similar magnitude produce few or none. We conducted a series of numerical simulations using MDOODZ 7.0, a geodynamic modeling framework, to systematically investigate the factors controlling subduction zone geometries. By varying key parameters, including plate convergence velocity, the thicknesses of continental and oceanic lithospheres, and the age of the oceanic plate, we identified the conditions that lead to the development of contrasting subduction regimes, specifically flat versus steep subduction geometries. To gain insights on the pore-fluid dynamics in different subduction geometries, we explored the variations in fluid release by coupling the geodynamic models with Perple_X calculations, which allowed us to model the interaction between the evolving fault zones and the dehydration reaction boundaries under varying pressure-temperature conditions. Furthermore, we quantified the amount of fluid released during these reactions and determined their depth within the subduction zone. Our preliminary results suggest that the depth of serpentinite dehydration occurs around ~60 km. These findings will be correlated with regions of increased seismic activity and higher aftershock density.