Lithospheric Structure of the Hikurangi Subduction Margin

Manusha Pasan Sanjaya Herath Herath Mudiyanselage

doi:10.26686/wgtn.14653491.v2

Abstract

Lithospheric Structure of the Hikurangi Subduction Margin

Highlights

1.1 Context and RationaleNew Zealand straddles the tectonic plate boundary between the Pacific and Australian Plates (Figure 1.1)
We infer that it is a result of hydration through bending-induced normal faults and/or the enhancement of crack porosity originally formed by thermal cracking
The upper and lower bands of seismicity in the double seismic zone observed in the southern Hikurangi margin are likely to be due to dehydration of the altered gabbroic crust and the mantle serpentinite, respectively

Summary

Introduction

1.1 Context and RationaleNew Zealand straddles the tectonic plate boundary between the Pacific and Australian Plates (Figure 1.1). The southern segment of the Hikurangi margin is characterised by frontal accretion whereas the northern segment is characterised by subducting seamounts and tectonic erosion [Wallace, 2020] These variations in character make the Hikurangi margin an ideal location to understand the subduction dynamics associated with an oceanic plateau and the full spectrum of fault slip modes of a subduction thrust. Subduction zones have the capacity to recycle water back into the mantle [Cai et al, 2018; Ranero et al, 2003; Shillington et al, 2015] because bending of the subducting plate at the outer rise and trench creates avenues for hydration down to ∼30 km into the mantle [Cai et al, 2018; Emry and Wiens, 2015; Faccenda et al, 2009] Seismic evidence from both passive and controlled-source studies show that a low-velocity region is created in the crust and upper mantle at the point of maximum bending in subduction zones. S-wave velocity information is more important than P-waves when performing dynamic rupture simulations of earthquakes and predicting associated ground shaking [e.g. Joyner, 2000; Kaneko et al, 2019]

Objectives

Methods

Results

Discussion

Conclusion