Multi-level magmatic system of El Hierro Island (Canary Islands) constrained by multi-satellite radar interferometry measurements during the 2011-2012 eruption

Starting from July 2011, anomalous seismicity was observed at El Hierro Island (Canary Islands, Spain). During the following three months, seismic activity increased both in number of events and in magnitude, while expanding over a large area. In early October 2011 the process led to a submarine eruption, with some uncertainty about the location and timing of vent(s) opening. The site of the eruption was ~10 km from the initial and main earthquake loci, indicative of significant lateral migration. Here, we conduct a multi-frequency, multi-sensor interferometric analysis of space-borne radar images acquired using three different satellites (Radarsat-2, ASAR-ENVISAT and COSMO-SkyMed). Radar interferometry is used to measure the deformation that occurred from December 2009 to July 2012. InSAR data fully captures both the pre-, co- and post-eruptive phases. Subsequently, elastic modeling of the ground deformation is employed to constrain the dynamics associated with the magmatic and eruptive activity. This study represents one of the first geodetically-constrained active magmatic plumbing system model for any of the Canary Islands volcanoes, and one of the few examples of geodetic measurement of submarine volcanic activity to date. It reveals a complex magmatic system with multiple levels of stagnation, a deeper central system (~8.5 km depth) and a shallower magma reservoir at the flank of the southern rift (~4 km depth). Before eruption, magma propagated ~5 km downrift towards the eruption fissure. From mid-November 2011 to early January 2012 the system was continuously recharged from source(s) deeper than 10 km, which contributed to a relatively atypical long duration for a basaltic eruption (~5 months). The submarine eruption finished on early March 2012. However, on June 24, 2012 the seismic activity resumed and intense ground deformation has been recorded. The anomalous seismicity continued for a month depicting a clear, but different migration path with respect to the previous period. At the time of the writing of this abstract (early August 2012), the activity has subsided. The most recently acquired InSAR (Radarsat-2 and COSMO-SkyMed) data will be presented and interpreted. The El Hierro Island magmatic plumbing system is a much more complex system that previously believed. It is composed with at least three main stagnation levels, i) a petrologically-constrained level at 20-26 km depth, ii) a level at the moho, base of the oceanic crust at 8-12 km depth, and iii) a 4 km depth level at the base of the volcanic edifice, coinciding with the typical seafloor depth at El Hierro region. Acknowledgments: Our research was supported by an Ontario Early Researcher Award, the CSRN NSERC Strategic Network Grant, and the NSERC, and the Banting Postdoctoral Fellowship. Additional support was provided by the Spanish MICINN project AYA2010-17448, and the Moncloa Campus of Excellence (UCM-UPM, CSIC). Data was provided by ESA (European Space Agency) through project CAT1:6745; CSA (Canadian Space Agency) by SOAR-E project #28209; and ASI (Italian Space Agency) SAR4Volcanoes project (agreement I/034/11/0).