High Rate GPS data on Augustine volcano (Alaska, USA) during the 2006 eruption

Transient episodes of ground displacement related to the dynamics of magmatic fluids as possible precursors to eruptive activity can be revealed through a careful analysis of high rate GPS (HRGPS) data. In the very first phases of an eruption the real time processing of high rate GPS data can be used by civil protection authorities to monitor the opening of fractures field on the slopes of volcanoes. During eruption, large explosions, opening of vents, migration of fractures fields, landslides and other dangerous phenomena can be monitored and their potential for damage estimated. This technique has already revealed its importance during the 2002-2003 Stromboli Island (Italy) eruption (Mattia et al., GRL, 2004). In this work, we have processed the GPS data of the stations on Augustine volcano spanning from August 2005 to February 2006. The sub-daily time series of the coordinates (15 minute medians) show clear evidences of the dynamic leading to the 2006 eruption and the 15 sec. data time series of some peculiar periods, gives new insights in the fast processes acting before and during the eruption. We also show the first results of a dynamic modelling of the volcanic sources acting during this last eruption of Augustine.