Global Analysis of Seismogenic Zone Temperatures at Convergent Margins

Knowledge of the controls on temperature distribution at subduction zones is critical for understanding a wide range of seismic, metamorphic, and magmatic processes. Recent studies at the Nankai, Middle America, and Cascadia margins suggest the thermal effects of fluid circulating in a highly permeable upper oceanic crust aquifer significantly redistributes heat in the subducting plate over large horizontal distances and widens the rupture area for great earthquakes. Here we present the results of ~220 2-D finite element model simulations covering the majority of known convergence rates, incoming plate ages, and plate dips. These simulations quantify the thermal effects of fluid circulation in the oceanic crust by comparing results with and without the effects of advective heat transfer in the aquifer. We find that fluid circulation has a large effect on subduction zone temperatures for scenarios with a small thermal parameter φ = Avsin(θ), where A is plate age, v is convergence rate, and θ is plate dip (at 40 km depth). Incoming plate age is the primary control on the effectiveness of advective heat transfer in the aquifer, and the greatest temperature effects occur with incoming plate <20 Ma. The thermal effects of fluid circulation drop off rapidly with increasing incoming plate age. The maximum temperature differences between cases with and without fluid circulation occur at ~40 - 55 km depth in all simulations. For incoming crust with the same φ value, steeper slab dip increases the thermal effect of fluid circulation. For most subduction zones with an incoming plate >20 Ma, the thermal effects of fluid circulation in the oceanic crust aquifer are small, and simple thermal models without fluid circulation are likely adequate.haded contour plot of the maximum temperature difference between no fluid flow and fluid flow cases for simulations with an average slab (θ = 26° at 40 km depth). Subduction zones recently modeled in detail with upper crust aquifer effects and subduction zones being considered for modeling are labeled with error bars.