Estimating volcanic deformation source parameters with a Finite Element inversion: the 2001-2002 unrest at Cotopaxi volcano, Ecuador
Journal of Geophysical Research. Solid Earth
American Geophysical Union (AGU)
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Deformation at Cotopaxi was observed between 2001 and 2002 along with recorded seismicity beneath the northeast (NE) flank, despite the fact that the last eruption occurred in 1942. We use electronic distance meter deformation data along with the patterns of recorded seismicity to constrain the cause of this unrest episode. To solve for the optimum deformation source parameters we employ inverse finite element (FE) models that account for material heterogeneities and surface topography. For a range of source shapes the models converge on a shallow reservoir beneath the southwest (SW) flank. The individual best fit model is a small oblate-shaped source, approximately 4–5 km beneath the summit, with a volume increase of roughly 20 × 106 m3. This SW source location contrasts with the NE seismicity locations. Subsequently, further FE models that additionally account for temperature-dependent viscoelasticity are used to reconcile the deformation and seismicity simultaneously. Comparisons of elastic and viscous timescales allude to aseismic pressurization of a small magma reservoir in the SW. Seismicity in the NE is then explained through a mechanism of fluid migration from the SW to the NE along fault systems. We extend our analyses to further show that if future unrest crises are accompanied by measurable seismicity around the deformation source, this could indicate a higher magma supply rate and increased likelihood of a forthcoming eruption.
The data informing this paper is available upon request to the lead author. This work was supported by the European Commission, Framework Program 7 (grant 282759, VUELCO, and grant 308665, MEDSUV), the Natural Environmental Research Council (NE/G01843X/1), and the Royal Society (UF090006). We thank reviewers A. Gudmundsson and L. Crescentini, and Editor A. Revil, for their comments which helped to improve the paper. We also thank Mark Jellinek for thoughtful discussions during manuscript preparation.
This is the final version of the article. Available from the publisher via the DOI in this record.
Vol. 120; doi: 10.1002/2014JB011731