GPS GEODETIC MONITORING OF SHORT TERM SURFACE DEFORMATION, SOUFRIERE HILLS, MONTSERRAT, LESSER ANTILLES

For nearly two decades, ground breaking geodetic surveys have been conducted on the active volcanic island of Montserrat in the Lesser Antilles island arc. Soufriere Hills Volcano (SHV) became active in 1995, and ever since, continuous GPS data have been gathered and processed using the latest and most advanced geodetic instruments and techniques available. The NSF-funded CALIPSO and SEA-CALIPSO projects have allowed for some of the most in depth studies of the ongoing SHV eruption to date. Data gathered from the early stages of the eruption in 1996 through 2010 from two continuous GPS sites, Hermitage Peak (HERM – located ~1.6 km from the vent) and Montserrat Volcano Observatory 1 (MVO1 – located ~7.6 km away from the vent), have been reprocessed using GIPSY-OASIS II (v. 6.1.2) with final, precise IGS08 orbits, clocks, and earth orientation parameters using an absolute point positioning (APP) strategy. Our study is being conducted to re-examine spatial and temporal changes in surface deformation, constrained by GPS, and to better illuminate the short term (i.e. sub-daily to weekly) deformation signals noted amongst the longer, cyclic deformation signals (i.e. monthly to annually) that have been previously reported and modeled. The reprocessed time-series show lower variance for daily APP solutions over the entire temporal data set; trends in the long-term inflation and deflation patterns are similar to those previously published (e.g. Elsworth et al., 2008; Mattioli et al., 2010; Odbert et al., 2012), but now superimposed, shorter term signals are more clearly visible. New elastic deformation models are being developed and will be presented for these short-term signals.