InSAR Observation of surface deformation at Augustine volcano, Alaska, 1992- 2006

Augustine volcano is a conical-shaped, active stratovolcano located southwest of Anchorage, Alaska. Augustine volcano experienced eight explosive eruptions in 1812, 1883, 1908, 1935, 1963, 1976, 1986, and most recently, January 2006. To measure ground surface deformation of the Augustine volcano, we applied satellite radar interferometry with European Remote Sensing Satellite 1 and 2 (ERS-1/2) and Environment Satellite (ENVISAT) Synthetic Aperture Radar (SAR) images acquired from three descending and three ascending satellite tracks. Multiple interferograms were stacked to detect the average deformation rate while reducing the effect of changes in atmospheric condition. To retrieve a temporal deformation sequence, we applied the Least-Squares method and Singular Value Decomposition method to a set of multiple-temporal interferograms. Interferograms before 2006 show about 3 cm/year subsidence, probably caused by the contraction and compaction of pyroclastic flow deposits from the 1986 eruption; no significant (i.e., larger than 2 cm) precursory inflation associated with the 2006 eruption was observed. After the January 2006 eruption, we detect rapid subsidence over the area of the 2006 pyroclastic flow deposits. The observed deformation from satellite radar interferometry agrees with the measurement from the Global Positioning System (GPS) network. This study demonstrates that satellite radar interferometry can be used to study the deformation of Augustine volcano to help understand the magma plumbing system and the characteristics of pyroclastic flows.