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Numerical Modeling of seismic wave propagation on Etna Volcano (Italy): Construction of 3D realistic velocity structures

Abstract : Understanding the source mechanism of long-period (LP) seismic signals on volcanoes is an important key point in volcanology and for the hazard forecasting. In the last decades, moment tensor inversions have led to various descriptions of the kinematic source mechanism. These inversions suppose a relatively simple structure of the medium. However, the seismic wave propagation in a realistic 3-D volcano model should be taken into account for understanding the complicated physical processes of magma and gas behaviors at depth. We are studying Etna volcano, Italy, to understand the volcanic processes during different stages of activity. We adopt a spectral element method (SEM), a code EFISPEC3D (De Martin, BSSA, 2011), which shows a good accuracy and numerical stability in the simulations of seismic wave propagation. First we construct the geometrical model. As surface strongly distorts waveforms we use a digital elevation model (DEM) to reproduce the free surface with a precision of 50 m. We then want to obtain numerical stability for waves with a frequency content until 3 Htz and for a shallow surface layer with Vs = 430 m/s. The minimal width of hexahedral elements required to obtain stability for such constraints in SEM is ~100 m. with a total number of element n = ~2 106 for the whole model. We then apply different velocity structure configurations. We start with a homogeneous medium and add complexities taking in account for a shallow low velocity structure and then apply a velocity gradient towards depth. Some vertical and horizontal structures can be added to reproduce injected dikes or sills respectively. Simulations performed in the homogeneous medium turn in approximately 20 hours for calculations parallelized on 16 CPUs. Complex velocity models should take approximately the same time of computation. We then try to simulate the ground motion from the LP sources (0.1-1.5 Hz) obtained by the inversion for the Etna volcano in 2008 (De Barros, GRL, 2009 and De Barros, JGR, 2011).
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https://hal-brgm.archives-ouvertes.fr/hal-00969115
Contributeur : Claudio Trovato <>
Soumis le : mercredi 2 avril 2014 - 10:07:31
Dernière modification le : mardi 31 mars 2020 - 09:02:11
Archivage à long terme le : : mercredi 2 juillet 2014 - 11:16:06

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  • HAL Id : hal-00969115, version 1

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Claudio Trovato, Hideo Aochi, Florent de Martin. Numerical Modeling of seismic wave propagation on Etna Volcano (Italy): Construction of 3D realistic velocity structures. EGU General Assembly 2014, Apr 2014, Wiens, Austria. ⟨hal-00969115⟩

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