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Numerical inversion of deformation caused by pressure sources: application to Mount Etna (Italy)
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Abstract
The interpretation of geodetic data in volcanic areas is usually based on analytical deformation
models. Although numerical Finite Element modeling allows realistic features such as topography
and crustal heterogeneities to be included, the technique is not computationally convenient
for solving inverse problems using classical methods. In this paper we develop a general tool to
perform inversions of geodetic data by means of 3D FE models. The forward model is a library
of numerical displacement solutions, where each entry of the library is the surface displacement
due to a single stress component applied to an element of the grid. The final solution is
a weighted combination of the six stress components applied to a single element-source. The
precomputed forward models are implemented in a global search algorithm, followed by an
appraisal of the sampled solutions. After providing extended testing, we apply the method to
model the 1993-97 inflation phase at Mt. Etna, documented by GPS and EDM measurements.
We consider four different forward libraries, computed in models characterized by homogeneous/
heterogeneous medium and flat/topographic free surface. Our results suggest that the
elastic heterogeneities of the medium can significantly alter the position of the inferred source,
while the topography has minor effect