The Significance of Heat Transport by Shallow Fluid Flow at an Active Plate Boundary: The Southern Alps, New Zealand

Fluid flow can influence fault behavior. Here we quantify the role of groundwater heat advection in establishing the thermal structure of the Alpine Fault, a major tectonic boundary in southern New Zealand that accommodates most of the motion between the Australian and Pacific Plates. Convergence on the Alpine Fault has rapidly uplifted the Southern Alps, resulting in high geothermal gradients and a thin seismogenic zone. A new equilibrium temperature profile from the 818 m‐deep Deep Fault Drilling Project 2B (DFDP‐2B) borehole has been interrogated using one‐dimensional analytical models of fluid and rock advection. Models indicate a total heat flux of 720 mW·m‐2 results from groundwater flow with Darcy velocities approximating to 7.8×10‐10 m·s‐1. Groundwaters advect significantly more heat than rock advection in the shallow orogen (<6 km depth) and are the major control on the subsurface temperature field.