Feasibility study for geodetic monitoring of Mt Ruapehu volcano, New Zealand, using GPS

Abstract

Global Positioning System (GPS) receivers were installed on Ruapehu volcano for a 10 month experiment to determine their utility for providing continuous real‐time deformation monitoring. Several processing runs were carried out to study the effects of ionospheric and tropospheric modelling and the use of predicted orbits on the noise levels of relative position determinations between receivers in the GPS network. Lowest noise levels were achieved with a system that solved for relative tropospheric delay between stations, and created a local ionosphere model using a dual frequency receiver. The use of predicted orbits rather than more accurate post‐processed orbits did not degrade the solutions for this small‐scale (6 km dimension) network. Our results imply that a real‐time system would detect relative vertical deformation that exceeds 25 mm and relative horizontal deformation that exceeds 10 mm over a several week period. Modelling of expected deformation leading to a small, shallow‐source (c. 1 km) eruption, with an associated pressure change of 106 Pa, indicated maximum vertical displacements of 40–70 mm could be expected at 300–600 m from the conduit centre, with horizontal displacements of 15–45 mm at 300–700 m. Such changes would be detectable by a real‐time GPS monitoring system.