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  • Publication
    Imaging magma storage below Teide volcano (Tenerife) using scattered seismic wavefields
    Tenerife (Canary Islands, Spain) is a volcanic island dominated by the Teide-Pico Viejo complex, with a summit height of 3718 m. After renewed signs of activity starting in 2004, an active seismic experiment was performed in 2007 to derive a tomographic model and identify seismic anomalies possibly associated with the magmatic system. To complement the tomography, a double beam-forming analysis is applied on two orthogonal 2-D profiles crossing the island to look for evidence of the existence of a magma chamber. Numerical tests allow us to investigate the best measure of coherency between traces, and show that the correlation and nth root semblance methods give better results than the classical semblance. They also demonstrate that the technique is reliable for locating scattering structures at depth, even when the velocity model is imperfect. Applying this technique to the Tenerife data set, two main anomalies can be identified: one at approximately 7–9 km b.s.l. depth in the northern part of the island, and one shallower (1–4 km b.s.l.) beneath the main summit. These structures could be linked to the magmatic system, in good agreement with previous studies. The shallowest one may be the phonolitic storage area feeding the Teide-Pico Viejo complex, while the deepest structure may be related to the basaltic system.
      509Scopus© Citations 20
  • Publication
    Moment tensor inversion for the source location and mechanism of long period (LP) seismic events from 2009 at Turrialba volcano, Costa Rica
    Long-period (LP) seismic events were recorded during the temporary installation of a broadband seismic network of 13 stations from March to September 2009 on Turrialba volcano, Costa Rica. Over 6000 LPs were extracted using a modified STA/LTA method and a family consisting of 435 similar LP events has been identified. For the first time at Turrialba volcano, full-waveform moment tensor inversion is performed to jointly determine the location and source mechanism of the events. The LPs in the family are likely to be caused by crack mechanisms dipping towards the southwest at angles of approximately 10 to 20°, located at shallow depths (< 800 m) below the active Southwest and Central craters. As the locations are so shallow, the most probable causes of crack mechanisms are hydrothermal fluids resonating within or 'pulsing' through a crack. The waveforms observed at the summit stations suggest a 'pulsing' mechanism, but source resonance with a high degree of damping is also possible.
      510Scopus© Citations 15