Magma Pathways and Their Interactions Inferred from InSAR and Stress Modeling at Nyamulagira Volcano, DR Congo

作者：Wauthier Christelle^*; Cayol Valerie; Smets Benoit; d'Oreye Nicolas; Kervyn Francois

来源：Remote Sensing, 2015, 7(11): 15179-15202.

DOI：10.3390/rs71115179

• radar interferometry
• numerical modeling
• non-linear inversion
• dike
• normal-stress
• Virunga
• East African Rift

A summit and upper flank eruption occurred at Nyamulagira volcano, Democratic Republic of Congo, from 2-27 January 2010. Eruptions at Nyamulagira during 1996-2010 occurred from eruptive fissures on the upper flanks or within the summit caldera and were distributed along the similar to N155E rift zone, whereas the 2011-2012 eruption occurred similar to 12 km ENE of the summit. 3D numerical modeling of Interferometric Synthetic Aperture Radar (InSAR) geodetic measurements of the co-eruptive deformation in 2010 reveals that magma stored in a shallow (similar to 3.5 km below the summit) reservoir intruded as two subvertical dikes beneath the summit and southeastern flank of the volcano. The northern dike is connected to an similar to N45E-trending intra-caldera eruptive fissure, extending to an similar to 2.5 km maximum depth. The southern dike is connected to an similar to N175E-trending flank fissure extending to the depth of the inferred reservoir at similar to 3.5 km. The inferred reservoir location is coincident with the reservoir that was active during previous eruptions in 1938-1940 and 2006. The volumetric ratio of total emitted magma (intruded in dikes + erupted) to the contraction of the reservoir (r(v)) is 9.3, consistent with pressure recovery by gas exsolution in the small, shallow modeled magma reservoir. We derive a modified analytical expression for r(v), accounting for changes in reservoir volume induced by gas exsolution, as well as eruptive volume. By using the precise magma composition, we estimate a magma compressibility of 1.9-3.2 x 10(9) Pa-1 and r(v) of 6.5-10.1. From a normal-stress change analysis, we infer that intrusions in 2010 could have encouraged the ascent of magma from a deeper reservoir along an similar to N45E orientation, corresponding to the strike of the rift transfer zone structures and possibly resulting in the 2011-2012 intrusion. The intrusion of magma to greater distances from the summit may be enhanced along the N45E orientation, as it is more favorable to the regional rift extension (compared to the local volcanic rift zone, trending N155E). Repeated dike intrusions beneath Nyamulagira's SSE flank may encourage intrusions beneath the nearby Nyiragongo volcano.

• 出版日期2015-11