Temporal Evolution of the Magmatic System at Tungurahua Volcano, Ecuador, detected by geodetic observations

Abstract

Changes in the pathway and timescale of magma ascent can be responsible for variations in eruptive style during long-lived eruptions, but are only documented at a small number of well-instrumented systems. Here we integrate PS-InSAR from high resolution TerraSAR-X radar imagery with continuous GPS data from 4 sites at Tungurahua volcano, Ecuador. Our results show long-term uplift between 2011-2014 associated with a continuously in ating prolate reservoir at a depth of 10 km beneath the summit. Comparisons with eruptive flux, taking compressibility into account, suggest that during this time period slightly over half the magma supplied to the system was erupted. The observations span three distinct phases of eruption and in 2012-2013, an increase in eruptive activity was accompanied by uplift on the volcano's western flank. Similar episodes have previously been observed during large Vulcanian eruptions and we attribute them to intrusions into an area of mechanical weakness. A localised patch of subsidence mid-way up the Tungurahua's western flank is co-located with a swarm of shallow long-period seismicity and may represent a potential site for a development of a lateral vent. This study demonstrates that satellite geodetic techniques are capable of characterising the geodetic signature of transitions in eruptive style during long-lived andesitic eruptions although the deformation is cm-scale of steep volcanic edi fices.