Pyroclastic Flow Generated Tsunami Waves Detected by CALIPSO Borehole Strainmeters at Soufriere Hills, Montserrat During Massive Dome Collapse: Numerical Simulations and Observations
E. J. van BoskirkB. VoightP. WattsChristina WidiwijayantiG. S. MattioliDerek ElsworthD. HidayatA. T. LindeP. E. MalinJürgen NeubergS. I. SacksE. ShalevRodger SparksS. R. Young
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Dome (geology)
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Lava dome
Dome (geology)
Volcanology
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In volcanic domains, magma transport and pressure build-up induce high stress–strain perturbations in the surrounding volcanic edifice that may lead to volcanic flank movements and possible instability. In this study, we focus on the 2007 March–April episode of volcanic activity at Piton de la Fournaise (PdF) Volcano, La Réunion Island. This episode was associated with a large volume of emitted lava (240 × 106 m3) and a 340-m caldera collapse. We present observations of continuous seismic velocity changes measured using cross-correlations of ambient seismic noise over 10 yr at PdF. Overall, we observe a large velocity reduction starting a few days prior to the major 2007 April 2 eruption. Comparison of seismic velocity change measurements with observations of deformation from InSAR and GPS shows that the seismic velocity reduction coincided with a widespread flank movement starting at the time of injection of magma to feed an initial eruption, a few days before the 2007 April 2 eruption. We emphasize the potential of noise-based seismic velocity change measurements, together with geodetic observations, to detect and monitor possibly hazardous slope instabilities.
Caldera
Ambient noise level
Lateral eruption
Volcanic hazards
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Volcanic eruptions are often very destructive events, having a massive impact on the natural and human environment. In order to mitigate the effect of volcanic hazards such as pyroclastic flows, lahars and tsunamis it is necessary to closely monitor volcanoes. Ground surface deformation is recognised as a reliable indicator of an impending eruption and can give clues to magmatic processes at depth. This paper gives a brief overview of the techniques employed for volcano deformation monitoring and then reviews advances in the use of GPS for this purpose. Recommendations on the ideal GPS system infrastructure are made.
Lahar
Deformation monitoring
Natural hazard
Volcanology
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Seismic interferometry
Seismic Noise
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Seismic Tomography
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Abstract The identification and evaluation of trigger mechanisms for volcano flank instabilities and/or collapse represent a key issue for risk assessment in densely populated volcanic areas, as well as in long‐distance settings, particularly in case of island or coastal volcanoes. Here we address quantitatively the effects of external (seismic) and inner (magmatic) forcing on the stress‐strain state associated to flank instabilities at Mount Etna (Sicily, southern Italy) by means of a 2‐D finite difference method numerical modeling. Modeled seismic actions include strong near‐field, strong far‐field, and low‐magnitude near‐field earthquakes. Magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area. Model results are validated in light of available monitoring data and recent eruptive activity. Numerical results show that the main strain effects are produced by high‐magnitude near‐field earthquakes (expected return time of ~10 3 yrs) and by vertical uprise of a magma dike below the volcano summit area. Maximum displacements in the order of tens of centimeters may involve the summit area, up to some 10 6 m 3 /m over some kilometers laterally. Stress releases up to 10 7 Pa may affect a limited portion of the magmatic conduit, thus favoring major effusive flank eruptions. Major catastrophic events, such as volcano flank collapse, should not be expected by applying, either individually or combined, the aforementioned actions.
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