InSAR and GPS ground deformation measurements along the Kivu segment of the East African Rift System during the 2011-2012 Nyamulagira volcanic eruption.
Abstract
Along the East African Rift System (EARS) lie several active volcanoes characterized by different eruptive styles and magma plumbing systems. Furthermore, along the EARS, magma intrusions represent a major component in continental rifting. In this unique tectonic environment it is very important to study the magma emplacement mechanisms. One of the most active volcanoes along the western branch of the EARS is the Nyamulagira (Democratic Republic of Congo), a basaltic shield volcano with a central caldera and an intermittent lava lake. From 1948 to 2012, Nyamulagira mostly showed a particular eruptive cycle with 1) classical short-lived (i.e. 20-30 days) flank eruptions, sometimes accompanied with intracrateral activity, which occurred every 1-4 years on average, and 2) less frequent long-lived (i.e. several months) distal (>8 km from the central caldera) eruptions usually emitting larger volumes of lava. Here we used InSAR data from different satellite (Envisat, Cosmo SkyMed, TerraSAR-X and RADARSAT) and GPS data from permanent stations in the KivuGNet network to measure ground displacement associated with 2011-2012 Nyamulagira distal eruption. Furthermore, using analytical models we invert the InSAR measured ground displacements to evaluate the deformation source parameters and the mechanism of magma emplacement. GPS data are used to validate the modeled displacements. Both InSAR and GPS observations show that strong ground deformation start two days before the eruption. Furthermore, seismic activity increased since November 4 2011, with long- and short-period earthquakes swarms. These are the evidences that the eruption was preceded by a magma intrusion that correspond to the migration of magma from a shallow reservoir ( 3km) below the caldera to the two eruptive fissures located 11 km ENE of the central edifice. Moreover, GPS, InSAR and seismic data suggest the presence of a deep magmatic source that possibly fed the shallower magmatic system. This mechanism, involving a deep source for this large eruption, contrasts with the usual shallow plumbing system identified during the classical flank eruptions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.V53C3133N
- Keywords:
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- 8419 Volcano monitoring;
- VOLCANOLOGYDE: 8434 Magma migration and fragmentation;
- VOLCANOLOGYDE: 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGYDE: 8486 Field relationships;
- VOLCANOLOGY