DECADAL DEFORMATION PATTERNS OF THE ACTIVE YELLOWSTONE VOLCANIC SYSTEM: INSIGHTS FROM GEODETIC GPS AND MULTI-SENSOR INSAR OBSERVATIONS (1992–2023)

The Yellowstone volcanic system is renowned for its episodic deformation, and this study delves into its intricacies using 10 Global Positioning System (GPS) stations and multi-sensor Synthetic Aperture Radar Interferometry (InSAR) data covering the 1992–2023 period. The research reveals widespread crustal deformation at three distinct locations: the Sour Creek and Mallard Lake resurgent domes within the caldera, and the Norris Geyser Basin (NGB) at the caldera's northwestern rim. Throughout the 31-year observation period, eight discernable episodes of caldera inflation and deflation were identified: Episode 1 (1992–1995): a deflation rate of approximately 2.7 cm/yr across the caldera floor. Episode 2 (1996–2000): minimal caldera deflation (0.5 cm/yr) along with NGB inflation (about 1.7 cm/yr). Episode 3 (2000–2004): slight caldera deflation (0.7 cm/yr) and NGB inflation (0.6 cm/yr). Episode 4 (2004–2009): extraordinary caldera inflation (3–8 cm/yr) accompanied by NGB deflation (1–4 cm/yr). Episode 5 (2010–2014): notable caldera-wide deflation (1–2.4 cm/yr). Episode 6 (2014–2015): remarkable caldera-wide inflation (2–5 cm/yr) and considerable NGB deflation (2–4 cm/yr). Episode 7 (2015–2022): broad caldera deflation (3–4 cm/yr) along with rapid NGB inflation (3–4.5 cm/yr) until 2020, followed by a local pause at NGB until 2022. Episode 8 (2022–2023): a pause in long-term caldera deflation, accompanied by 3-3.5 cm of NGB deflation since October 2022. Data from ERS-1/-2, ENVISAT, and Sentinel-1A/-1B satellites were processed using conventional two-pass and advanced small baseline subset approaches. Inverse modeling of combined GPS and InSAR measurements suggests the presence of two discrete planar sources beneath the Yellowstone caldera and NGB, located at depths of 8–12 km and 10–16 km, respectively. Notably, major fault zones within the intermittently active caldera do not appear to control the observed deformation patterns. Instead, they likely served as conduits for migrating magma and hydrothermal fluids. Consequently, the observed deformation is attributed primarily to magma charge and discharge processes, along with hydrothermal activities. This study enhances our understanding of the volcanic system's dynamics and contributes valuable insights into its geological processes.