Dynamics of episodic magma injection and migration at Yellowstone
caldera: revisiting the 2004-2009 episode of caldera uplift with InSAR
and GPS data
Abstract
The 2004-2009 caldera uplift is the largest instrumentally recorded
episode of unrestat Yellowstone caldera. We use GPS and InSAR time
series spanning 2004-2015, witha focus in the aforementioned event to
understand the mechanisms of unrest. InSARdata recorded∼25 and∼20 cm of
uplift at the Sour Creek (SCD) and Mallard Lake(MLD) resurgent domes
during 2004-2009, and∼8 cm of subsidence at the NorrisGeyser Basin (NGB)
during 2004-2008. The SCD/MLD uplift was followed by sub-sidence across
the caldera floor with a maximum at MLD of∼1.5-2.5 cm/yr and
nodeformation at NGB. The best-fit source models for the 2004-2009
period are two hori-zontal sills at depths of∼8.7 and 10.6 km for the
caldera source and NGB, respectively,with volume changes of 0.354 and
-0.121 km3, and an overpressure of∼0.1 MPa. TheInSAR and GPS time series
record exponentially increasing followed by exponentiallydecreasing
uplift between 2004 and 2009, which is indicative of magma injection
intothe caldera reservoir. However, magma extractionfrom NGB to the
caldera is unable to explain the subsidence coeval with the
calderauplift. Models of magma injection can also explain other episodes
of caldera uplift likethat in 2014-2015. Distributed sill opening models
show that magma is stored acrossthe caldera source with no clear
boundary between MLD and SCD. Since the magmaoverpressure is orders of
magnitude below the tensile strength of the encasing rock,historical
episodes of unrest like these are very unlikely to trigger an eruption.