New Zealand-Wide Geodetic Strain Rates Using a Physics-Based Approach

Abstract

We present a new strain rate map for New Zealand, based on geodetic data acquired from 1995 to 2013. We use a physics-based approach, which inverts the horizontal GPS velocities for Vertical Derivatives of Horizontal Stress (VDoHS) rates, relying on using elasticity theory and the horizontal force balance equations at the Earth's surface. The VDoHS rates are then integrated to obtain horizontal strain rates. Strain rates derived using this new approach are less spatially smoothed than previous results using conventional methods. In addition to the major plate boundary features in New Zealand, low-rate zones of deformation are resolved by the strain and VDoHS rates, which bodes well for the utility of this method to reveal processes on hidden or ill-characterized fault zones. Application of this new method to obtain strain and VDoHS rates provides the highest resolution view to-date of contemporary deformation in New Zealand.