Earthquake Triggering of Volcanic Unrest in Ecuador at Guagua Pichincha and Chiles-Cerro Negro Constrained by InSAR Data

After every significant earthquake there is concern of whether the earthquake may trigger volcanic unrest and/or an eruption. Here we present two case studies of inflation following shallow earthquakes using Sentinel-1 and TerraSAR-X InSAR time series data at Guagua Pichincha and Chiles volcanoes in Ecuador in the Northern Andes. For dacitic Guagua Pichincha volcano we show that the central dome started to inflate after the April 2016 Mw 7.8 subduction earthquake at ~160 km distance. The deformation data are consistent with a shallow hydrothermal source at a ~2 km depth above sea level. Inflation continued until mid 2019. There were periods of inactivity or slight deflation before the 2016 earthquake and then after 2019. In 2014 a swarm of volcano-tectonic seismic events and a shallow earthquake of Mw 5.6 occurred south of Chiles volcano [Ebmeier et al., 2016]. Sentinel-1 time series data show that the volcano inflated through 2020 at a rate of 2-4 cm/yr. The data are consistent with the presence of a magmatic source at the depth of ~9 km below sea level located southeast of Chiles volcano that continuously inflated during the time period of our observations. It is unclear whether the inflation started after the earthquake as we lack InSAR observations for the 2011-2014 period. No inflation was detected during 2007-2011 [Morales-Rivera et al., 2016]. We present stress change calculations to investigate whether the 2014 earthquake could have triggered the inflation of this magmatic source.