Contemporary ground deformation in the Taupo Rift and Okataina Volcanic Centre from 1998 to 2011, measured using GPS

Abstract

The Taupo Volcanic Zone (TVZ) is one of the world's most productive regions of rhyolitic volcanism and contains the highly active Okataina Volcanic Centre (OVC). Within the TVZ, intra-arc extension is expressed as normal faulting within a zone known as the Taupo Rift. The OVC is located within a complex part of the rift, where volcanism and deformation is considered influenced by rift structure and kinematics. There has been significant research on the structural, volcanic and geophysical properties of the rift and OVC, but less focus on deformation using geodetic data. The limited studies that have utilized geodetic data do not clearly resolve the distribution of deformation and strain rates within the rift and OVC. This is essential to ensure that deformation signals from volcanic processes at the OVC are correctly identified and distinguished from those related to regional tectonic or local hydrothermal processes within the rift. In this paper, we present a picture of contemporary deformation at the OVC and within the surrounding rift in detail, using existing and new GPS campaign and continuous GPS (cGPS) data collected between 1998 and 2011. The results show a highly heterogeneous deformation and strain rate field (both extension and shortening) through the study area, partitioned into different parts of the rift. Our results agree well with earlier geodetic studies, as well as identify new features, but some deformation patterns conflict with long-term geological observations. In the OVC, we observe a locally rotated horizontal velocity field, significant vertical deformation and variable strain rates across the caldera. In the Tarawera Rift, we identify elevated extension and shear rates, which may have significant implications for volcanism there. A shortening pattern is identified through the central rift, which is unexpected in an intra-arc rifting environment. We attempt to explain the source/s of shortening and extension and discuss their implications for geodetic monitoring efforts in the OVC.