The Thermal Regime of Shallow and Deep Slow Slip associated with the Hikurangi Trough, New Zealand

Harris, Robert

The Thermal Regime of Shallow and Deep Slow Slip associated with the Hikurangi Trough, New Zealand

Tuesday, 23 February 2016

Robert N Harris¹, Anson Antriansian¹, Anne M Trehu², Stuart A Henrys³, Andrew R Gorman⁴, Rachel M Lauer⁵, Benjamin J Phrampus⁶, Harmony Colella⁷, Dylan Baker⁴ and Nicole Rocco², (1)Oregon State University, Collage of Earth, Oceanic and Atmospheric Sciences, Corvallis, OR, United States, (2)Oregon State University, Corvallis, OR, United States, (3)GNS Science, Lower Hutt, New Zealand, (4)University of Otago, Department of Geology, Dunedin, New Zealand, (5)Organization Not Listed, Washington, DC, United States, (6)Southern Methodist University, Dallas, TX, United States, (7)Arizona State University, Tempe, AZ, United States

Abstract:

The Hikurangi Trough, formed by the subduction of the Hikurangi Plateau beneath New Zealand’s North Island, exhibits strong along-strike changes in the distribution and characteristics of slow slip events (SSEs). SSEs associated with the northern Hikurangi Trough occur at shallow depths (< 15 km) and last approximately 1-2 weeks. SSEs associated with the southern Hikurangi Trough occur at deeper depths (> 20-30 km) and have longer durations. These variations are associated with along strike changes in the character of basement relief and sediment thickness.

To better understand the thermal regime of both of these areas we collected seafloor heat flow values along a series of transects consisting of closely-space measurements with a 3.5 m “violin-bow” type probe. Our measurements confirm that the background heat flow on the incoming plate in both regions is approximately 50 mW/m² consistent with cooling plate models for 120 Ma oceanic crust. In regions of bathymetric relief and relatively thin sediment cover that characterize the northern region, heat flow values show clear evidence of crustal fluid flow. Heat flow values in the southern area, characterized by smooth basement relief and relatively thick sediment, do not require crustal fluid flow. We are developing 2D thermal models for each region to understand the thermal and hydrologic regimes.