Source mechanism of long-period events recorded by a high-density seismic network during the 2008 eruption on Mount Etna

Source mechanism of long-period events recorded by a high-density seismic network during the 2008 eruption on Mount Etna De Barros L. auteur aut IRD Lokmer I. auteur aut IRD Bean C. J. auteur aut IRD O'Brien G. S. auteur aut IRD Saccorotti G. auteur aut IRD Métaxian Jean-Philippe auteur aut IRD Zuccarello L. auteur aut IRD Patane D. auteur aut IRD text journalArticle eng One hundred twenty-nine long-period (LP) events, divided into two families of similar events, were recorded by the 50 stations deployed on Mount Etna in the second half of June 2008. During this period lava was flowing from a lateral fracture after a summit Strombolian eruption. In order to understand the mechanisms of these events, we perform moment tensor inversions. Inversions are initially kept unconstrained to estimate the most likely mechanism. Numerical tests show that unconstrained inversion leads to reliable moment tensor solutions because of the close proximity of numerous stations to the source positions. However, single forces cannot be accurately determined as they are very sensitive to uncertainties in the velocity model. Constrained inversions for a crack, a pipe or an explosion then allow us to accurately determine the structural orientations of the source mechanisms. Both numerical tests and LP event inversions emphasise the importance of using stations located as close as possible to the source. Inversions for both families show mechanisms with a strong volumetric component. These events are most likely generated by cracks striking SW-NE for both families and dipping 70 degrees SE (family 1) and 50 NW (family 2). For family 1 events, the crack geometry is nearly orthogonal to the dikelike structure along which events are located, while for family 2 the location gave two pipelike bodies that belong to the same plane as the crack mechanism. The orientations of the cracks are consistent with local tectonics, which shows a SW-NE weakness direction. The LP events appear to be a response to the lava fountain occurring on 10 May 2008 as opposed to the flank lava flow. specialized 066 Journal of Geophysical Research.Solid Earth 116 B01304 2011 0148-0227 https://www.documentation.ird.fr/hor/PAR00006495 10.1029/2010jb007629 0148-0227 https://www.documentation.ird.fr/hor/PAR00006495 IRD - Base Horizon / Pleins textes 2011-03-04 2017-08-23 PAR00006495 fre