Yellowstone Volcanic Unrest from GPS and SAR Interferometric Observations between 1992 and 2015

Abstract:

Incorporating geodetic measurements from nine Global Positioning System (GPS) stations and multi-sensor Interferometric Synthetic Aperture Radar (InSAR), six prominent episodes of Yellowstone caldera unrest are identified between 1992 and 2015. Episode 1: 1992–1995, deflation rate of about 2.7 cm/yr, episode 2: 1996–2000, minimal deflation of 0.5 cm/yr with considerable inflation of 1.7 cm/yr at Norris, episode 3: 2000–2004, slight deflation of 0.7 cm/yr with local inflation of 0.6 cm/yr at Norris, episode 4: 2004–2009, extraordinary inflation of 3–8 cm/yr with substantial deflation of 1–4 cm/yr at Norris, episode 5: 2010–2014, notable deflation of about 1–2.4 cm/yr across the entire caldera floor, and ultimately episode 6: 2014–2015, remarkable caldera-wide inflation of about 2-6 cm/yr. During the period of observation (1992–2015), extensive deformation has occurred primarily at three locations; namely, the Mallard Lake resurgent dome, the Sour Creek resurgent dome, and the Norris Geyser Basin that is located nearby the northwestern rim of the caldera. InSAR data acquired during 1992–2015 by ERS-1, ERS-2, ENVISAT, TerraSAR-X, TanDEM-X, and Sentinel-1 are analyzed using the two-pass and the small baseline subset interferometric methods. The created interferograms do not show any alignment of crustal deformation with fault zones across the intermittently active caldera, which indicate that the magma charge and discharge, as well as the widespread hydrothermal activity are responsible for the induced deformation. Fault zones most likely have acted as pathways for the movements of magma and hydrothermal fluids, but they do not have any influence on the measured rates of surface motion. Source modeling of recent GPS and InSAR measurements indicates the existence of two distinct planar sources beneath the caldera (8–12 km) and the Norris Geyser Basin (10–16 km).