Ground deformation in a viscoelastic medium composed of a layer overlying a half-space: a comparison between point and extended sources |
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Authors: | Arnau Folch,José Ferná ndez,John B. Rundle,& Joan Martí |
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Affiliation: | Institute of Earth Sciences 'Jaume Almera' (CSIC), c/Lluís SoléSabarís s/n, 08025 Barcelona, Spain;, Instituto de Astronomía y Geodesia (CSIC-UCM), Facultad de C. Matemáticas, Ciudad Universitária, 28040 ;Madrid, Spain. E-mail: , CIRES, University of Colorado at Boulder, CO 80389, USA, |
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Abstract: | We obtain and compare analytical and numerical solutions for ground displacement caused by an overpressurized magma chamber placed in a linear viscoelastic medium composed of a layer over a half-space. Different parameters such as size, depth and shape of the chamber, crustal rheology and topography are considered and discussed. Numerical solutions for an axisymmetric extended source are computed using a finite element method (FEM). Analytical solutions for a point source are obtained using the dislocation theory and the propagator matrix technique. In both cases, the elastic solutions are used together with the correspondence principle of linear viscoelasticity to obtain the solution in the Laplace transform domain. Viscoelastic solutions in the time domain are derived inverting the Laplace transform using the Prony series method. The differences between the results allow us to constrain the applicability of the point source and the flat surface hypothesis, which are usually implicitly assumed when analytical solutions are derived. The effect of the topography is also considered. The results obtained show that neglecting the topographic effects may, in some cases, introduce an error greater than that implicit in the point-source hypothesis. Therefore, for an adequate modelling and interpretation of the time-dependent displacements, topography must be considered. |
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Keywords: | analytical model ground deformation magmatic intrusion numerical model viscoelasticity. |
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