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Authors: | De Barros, L.* Lokmer, I.* Bean, C. J.* O'Brien, G. S.* Saccorotti, G.* Métaxian, J.-P.* Zuccarello, L.* Patanè, D.* |
Title: | Source mechanism of long-period events recorded by a high-density seismic network during the 2008 eruption on Mount Etna | Journal: | Journal of Geophysical Research | Series/Report no.: | /116(2011) | Publisher: | American Geophysical Union | Issue Date: | 2011 | DOI: | 10.1029/2010JB007629 | URL: | http://www.agu.org/pubs/crossref/2011/2010JB007629.shtml | Keywords: | Etna Volcano long-period events source mechanism location plumbing systems |
Subject Classification: | 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring |
Abstract: | 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° 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. |
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