EGU24-6837, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-6837
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Neotectonic stress characterization of New Zealand along the Australia–Pacific plate boundary 

Mojtaba Rajabi1, Moritz Ziegler2,3, Oliver Heidbach2, and Malte Ziebarth2,3
Mojtaba Rajabi et al.
  • 1The University of Queensland, School of the Environment, Brisbane, Australia (m.rajabi@uq.edu.au)
  • 2Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany
  • 3Technical University of Munich, Munich, Germany

The complex interplay between the Pacific and Australian plates in New Zealand offers a unique opportunity to investigate the present-day stress field in a tectonically active area. This study examines the present-day stress pattern of New Zealand through the analysis and compilation of data from 289 boreholes, 4291 earthquake focal mechanism solutions, and 72 neotectonic geological structures. Utilizing the Moho depth of New Zealand, we developed both crustal and mantle stress maps. Stress data above the Moho depth is categorized as the crustal stress map, while data below the Moho is classified as the mantle stress map.

The crustal stress map reveals a consistent ESE-WNW orientation of the maximum horizontal stress (SHmax) across much of the South Island, presenting a high angle to the strike of major active strike-slip faults. In the North Island, the crustal SHmax pattern is variable, highlighting the predominant role of the Pacific Plate subduction beneath the Australian Plate along the Hikurangi Margin. Within the Hikurangi Subduction Zone, both the crustal and mantle SHmax orientations are variable. However, the Taupo Rift Zone exhibits completely different stress pattern in mantle and crust, highlighting the Moho as a strong decoupling horizon in this region.

An examination of neotectonic stress regimes, derived from the neotectonic fault database, in comparison with the present-day stress regime from our stress database across 28 tectonic domains in New Zealand indicates a correlation between observed faults, faulting styles, and the stress field. Nevertheless, discrepancies emerge in certain domains, where the acting stress field diverges from the one expected according to the observed faults, suggesting non-optimal fault orientations.

How to cite: Rajabi, M., Ziegler, M., Heidbach, O., and Ziebarth, M.: Neotectonic stress characterization of New Zealand along the Australia–Pacific plate boundary , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6837, https://doi.org/10.5194/egusphere-egu24-6837, 2024.