RECENT TECTONO-VOLCANIC ACTIVITY IN THE EASTERN SNAKE RIVER PLAIN AND YELLOWSTONE INFERRED FROM SAR INTERFEROMETRY

Synthetic Aperture Radar Interferometric (InSAR) data acquired at the C-band between 1992 and 2007 have been used to detect and measure recent tectono-volcanic activity in the Eastern Snake River Plain (ESRP) and Yellowstone Plateau. InSAR results show that no regionally consistent subsidence or uplift occurred in the Line-Of-Sight direction across the central part of ESRP during the periods of observations. However, local surface movements of 1-3 cm magnitude have been detected in the adjacent Basin-Range province. Slight differential surface movements along three major normal faults (Centennial, Madison, and Hebgen faults) have been also detected between 1993 and 2006. Just southwest of Island Park, along the ESRP axial volcanic zone, the time-series of differential interferograms show a cycle of uplift (+1 cm/yr) between 1993 and 2000. One hypothesis for this uplift is crustal magma injection. Beneath the active Yellowstone caldera, magma chamber activity is observed from independent differential interferograms and is marked by cycles of subsidence (-1 cm/yr) during 1997-2000 and uplift (+3 cm/yr) during 2004-2006. The time-series of differential interferograms show that uplift in the axial volcanic zone near Island Park was coeval with subsidence in the active Yellowstone caldera. The detected interferometric signals may indicate a connection between the driving forces of surface deformation in the three adjacent regions.