Crustal Heat Flow and Thermal Modeling of the Hikurangi Trough, New Zealand

Graduation date: 2017Measuring surface heat flow at the Hikurangi Trough is key toward characterizing the local thermal regime and the influence of thermally sensitive processes such as fluid flow and slow slip. Marine heat flow data were collected during May– June 2015 in the northern Hikurangi Trough at sites seaward and landward of the deformation front, giving mean and one standard deviation values of 58 ± 16 and 46 ± 15 mW m⁻² respectively. A 3.5 m violin-bow style probe was used to measure thermal conductivity and temperature gradient of the seafloor, and heat flow is calculated using Fourier’s law. Two-dimensional steady-state, finite element modeling was undertaken to analyze the influence of subduction parameters on surface heat flow and temperature along the subduction thrust. Heat flow values seaward of the deformation front have been found to be sensitive to the structure of buried and outcropping extrusive crust, but the mean heat flow is within the range of expected values for lithosphere this age (120 Myr) according to the GDH1 cooling model. Landward of the deformation front, measured heat \ud flow is in excess of preferred modeled values. I interpret these observations as evidence for fluid flow within a crustal aquifer system and through splay faults within the forearc. A heat flow discontinuity of 40 mW m⁻² landward of the deformation front supports the presence of compaction sourced fluid along the subduction thrust, which is consistent with previous evidence for excess pore pressure and the occurrence of shallow slow slip