Open AccessEffect of mechanical heterogeneity in arc crust on volcano deformation with application to Soufrière Hills Volcano, Montserrat, West Indies
Author(s) -
Hautmann Stefanie,
Gottsmann Joachim,
Sparks R. Stephen J.,
Mattioli Glen S.,
Sacks I. Selwyn,
Strutt Michael H.
Publication year - 2010
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jb006909
Subject(s) - geology , volcano , crust , seismology , volcanic arc , cabin pressurization , terrane , magma chamber , geodetic datum , basalt , island arc , magma , petrology , subduction , tectonics , geochemistry , geodesy , engineering , aerospace engineering
Analyses of volcano surface deformation are commonly based on models that assume mechanical homogeneity of rocks surrounding the causative pressure source. Here we present a detailed study that shows the differences in deduced surface deformation caused by source pressurization accounting for either mechanical homogeneity or mechanical heterogeneity of encasing rocks in a volcanic arc setting using finite element models. Accounting for crustal heterogeneity from seismic data, we test for a range of source geometries and intermediate crustal depths and explore the misfits of deduced source parameters from the two families of models. In the second part of this study, we test the results from the generic study against cGPS data from two deformation periods (the 2003–2005 ground inflation and the 2005–2007 ground deflation) at Soufrière Hills Volcano, Montserrat, West Indies, to inform on source parameters. Accounting for a variable crustal rigidity with depth as deduced by seismic analysis beneath Montserrat, we find the data to be best explained by pressurization and depressurization of a slightly prolate midcrustal magma chamber that is centered between 11.5 and 13 km below sea level, about 640 m NE of the active vent. Considering source dimension and source pressure changes, we demonstrate that magma compressibility and viscoelasticity of host rocks considerably affect dynamics in the midcrustal magmatic system of Soufrière Hills Volcano and need to be accounted for as first‐order effects in geodetic data analyses and modeling.