Collaborative Research: Vertical Movement in the Southern Alps Constrained by GPS and Absolute Gravity

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9902981Bilham This is a collaborative project to measure vertical components of motion across the Southern Alps of New Zealand using both GPS geodesy and absolute gravity. The investigators will install seven continuous or semi-continuous GPS instruments along a profile across the Southern Alps where the range is especially high, and rates of vertical movement should also be high. They will measure g, using the FG5 gravity instrument at 10 sites, both to calibrate and supplement GPS measurements. Five years of data collection should allow a quantification of uplift of benchmarks with respect to sea-level, and a test of whether such uplift is compensated by crustal thickening or a response to erosional unloading. Vertical components of deformation should contribute to understanding two basic processes in continental tectonics; 1) how surface deformation is connected to that at depth, and 2) how climate, through erosion, affects tectonics. The combined use of absolute g and GPS geodesy should allow the PIs to distinguish the extent to which uplift results from the isostatic response to 1) the removal of a surface load and the uplift of the entire crust, or 2) to crustal thickening, for which the rate of thickening should be six to seven times the measured rate of uplift. The work involves extensive collaboration and cost sharing with international colleagues in New Zealand and elsewhere.