Balancing the plate motion budget in the South Island, New Zealand using GPS, geological and seismological data

Abstract

SUMMARY The landmass of New Zealand exists as a consequence of transpressional collision between the Australian and Pacific plates, providing an excellent opportunity to quantify the kinematics of deformation at this type of tectonic boundary. We interpret GPS, geological and seismological data describing the active deformation in the South Island, New Zealand by using an elastic, rotating block approach that automatically balances the Pacific/Australia relative plate motion budget. The data in New Zealand are fit to within uncertainty when inverted simultaneously for angular velocities of rotating tectonic blocks and the degree of coupling on faults bounding the blocks. We find that most of the plate motion budget has been accounted for in previous geological studies, although we suggest that the Porter's Pass/Amberley fault zone in North Canterbury, and a zone of faults in the foothills of the Southern Alps may have slip rates about twice that of the geological estimates. Up to 5 mm yr−1 of active deformation on faults distributed within the Southern Alps <100 km to the east of the Alpine Fault is possible. The role of tectonic block rotations in partitioning plate boundary deformation is less pronounced in the South Island compared to the North Island. Vertical axis rotation rates of tectonic blocks in the South Island are similar to that of the Pacific Plate, suggesting that edge forces dominate the block kinematics there. The southward migrating Chatham Rise exerts a major influence on the evolution of the New Zealand plate boundary; we discuss a model for the development of the Marlborough fault system and Hikurangi subduction zone in the context of this migration.

Shear behavior of DFDP-1 borehole samples from the Alpine Fault, New Zealand, under a wide range of experimental conditions

“…No large earthquake has occurred in the past 300 years, suggesting that a hazardous, large-magnitude earthquake on the Alpine Fault may be imminent (Sutherland et al 2007(Sutherland et al , 2012Townend et al 2009Townend et al , 2013. Geodetic measurements along the central segment of the fault indicate that the Alpine Fault is fully locked at depths of 5-8 km and partially locked up to ~18 km, and is loaded from below by the lower crust at a rate representing 50-70 % of the plate convergence rate (Beavan et al 1999Norris and Cooper 2000;Wallace et al 2007). The lack of measurable historic creep at the surface indicates that tectonic strain is balanced by earthquake slip (Beavan et al 1999).…”

Changes in hot spring temperature and hydrogeology of the Alpine Fault hanging wall, New Zealand, induced by distal South Island earthquakes

“…1). Contemporary deformation is dominated by deep-seated slip on the Alpine Fault and locking from depths shallower than approximately 13-18 km (see also Beavan et al 2007;Wallace et al 2007). During the Mw7.8 Dusky Sound earthquake, there were clear offsets *Estimated-PGV max times the shear modulus (3 9 10 10 Pa), divided by shear wave velocity (3.5 km sec À1 ).…”

Holocene rupture of the Repongaere fault, Gisborne: Implications for Raukumara Peninsula deformation and impact on the Waipaoa Sedimentary System

“…The Repongaere Fault lies within the uplifted forearc portion of the northern Hikurangi Subduction Margin, where the Pacific plate is being obliquely subducted beneath the australian plate at c. 47 mm/yr (Wallace et al 2007) (Fig. 1a).…”

“…hollow triangles represent volcanoes of the Taupo volcanic Zone (TvZ). Numbers by arrows are plate convergence rates (mm/yr) from Wallace et al (2007). B, major structural domains of the northern hikurangi margin.…”