CONTEMPORARY INSAR MEASUREMENTS OF GROUND DEFORMATION IN THE SNAKE RIVER PLAIN AND ITS ADJACENT BASIN-RANGE PROVINCE, IDAHO

The Snake River Plain (SRP) is a bow-shaped depression that is about 640-km long and 80-km wide. It covers approximately a quarter of the State of Idaho. SRP can be divided into eastern, central, and western sections. In this study, Synthetic Aperture Radar Interferometric (InSAR) data acquired during 1992-2010 have been used to measure contemporary ground deformation in the eastern SRP (eSRP) and its surrounding Basin-Range province. InSAR observations indicate regional subsidence of varying magnitudes (1-2 mm/yr) across eSRP with local uplift of about 2 mm/yr around some water bodies and agricultural fields. The regional subsidence is interpreted as a result of thermal contraction in the wake of the Yellowstone hotspot, though other interpretations are also possible. The local uplift is attributed to agricultural practices. Results show also local subsidence and uplift features of magnitudes about 2 mm/yr in the Pocatello/Chubbuck area. These features are most likely caused by groundwater processes. However, differential surface motions across unmapped faults are evident as well. Surprisingly, the InSAR measurements imply a rapid rate of ground subsidence (about 3-7 cm/yr) across the entire Raft River Valley (RRV) with a local anomaly of substantial uplift (3 cm/yr) at the location of the Raft River Geothermal Plant. These rapid rates of ground deformation are apparently related to the production of geothermal energy in RRV in southeastern Idaho. More InSAR analysis over the Boise area in the western SRP is currently underway and results will be presented during the meeting.