Options
O'Brien, G. S.
Loading...
Preferred name
O'Brien, G. S.
3 results
Now showing 1 - 3 of 3
- PublicationRestrictedAn integrated method to model volcanic processes and associated geophysical signals(2009)
; ; ; ; ; ; ; ; ;Vassalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Montagna, C. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;O'Brien, G. S.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland ;Bean, C. J.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland ;Bisconti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; ; ; ; We present a numerical approach for modelling the complex sub-surface volcanic processes and associated geophysical signals. This method is based on the one-way coupling of the dynamics of a magmatic system and the response of the host rocks. The two systems are modelled independently, by two different numerical codes, that solve the equations of motion for the magmatic fluid and the equation of elasto-dynamics for wave propagation in the surrounding medium, respectively. Synthetic geophysical signals can be obtained and compared with those recorded by monitoring networks. The final aim is to understand how the complex physics of magma dynamics, coupled to its hosting medium, translates into geophysical data that can be measured and interpreted in order to understand sub-surface magma dynamics and forecast the short-term volcanic hazard. We applied this method to the Campi Flegrei volcanic system (southern Italy) and investigated the convection and mixing dynamics induced by the arrival of new CO2-rich magma into a hypothetical shallow magma chamber. The pressure waves originated by this system are propagated in the surrounding rocks, and the associated broad-band ground displacement and gravity anomalies are evaluated at the Earth’s surface.266 64 - PublicationRestrictedSource mechanism of long-period events recorded by a high-density seismic network during the 2008 eruption on Mount Etna(2011)
; ; ; ; ; ; ; ; ;De Barros, L.; School of Geological Sciences, University College Dublin, Dublin, Ireland ;Lokmer, I.; School of Geological Sciences, University College Dublin, Dublin, Ireland ;Bean, C. J.; School of Geological Sciences, University College Dublin, Dublin, Ireland ;O'Brien, G. S.; School of Geological Sciences, University College Dublin, Dublin, Ireland ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Métaxian, J.-P.; LGIT, Université de Savoie-IRD-CNRS, Chambéry, France ;Zuccarello, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; ; 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.168 17 - PublicationOpen AccessSource geometry from exceptionally high resolution Long Period event observations at Mt Etna during the 2008 eruption.(2009-11-30)
; ; ; ; ; ; ; ; ;De Barros, L.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4 ;Bean, C. J.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4 ;Lokmer, I.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4 ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Zuccarello, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;O'Brien, G. S.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4 ;Metaxian, J. P.; Universite de Savoie-IRD-CNRS, 73376 Chambery, France ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; ; During the second half of June, 2008, 50 broadband seismic stations were deployed on Etna volcano in close proximity to the summit, allowing us to observe seismic activity with exceptionally high resolution. 129 Long Period events (LP) with dominant frequencies ranging between 0.3 and 1.2 Hz, were extracted from this dataset. These events form two families of similar waveforms with different temporal distributions. Event locations are performed by cross-correlating signals for all pairs of stations in a two-step scheme. In the first step, the absolute location of the centre of the clusters was found. In the second step, all events are located using this position. The hypocentres are found at shallow depths (0 to 700 m deep) below the summit craters. The very high location resolution allows us to detect the temporal migration of the events along a dike-like structure and 2 pipe shaped bodies, yielding an unprecedented view of some elements of the shallow plumbing system at Mount Etna. These events do not seem to be a direct indicator of the ongoing lava flow or magma upwelling.125 170