S. De Angelis
University of Liverpool
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Featured researches published by S. De Angelis.
Journal of Geophysical Research | 2008
G. Wadge; David G. Macfarlane; Henry M. Odbert; Michael James; J. K. Hole; Graham Ryan; V. Bass; S. De Angelis; Harry Pinkerton; Duncan A. Robertson; Susan C. Loughlin
range and intensity measurements of the change in summit lava (� 1.5 � 10 6 m 3 , 22%), (2) AVTIS range measurements to measure the talus growth (� 3.9 � 10 6 m 3 , 57%), and (3) rockfall seismicity to measure the pyroclastic flow deposit volumes (� 1.4 � 10 6 m 3 , 21%), which gives an overall dense rock equivalent extrusion rate of about 7 m 3 � s � 1 . These figures demonstrate how efficient nonexplosive lava dome growth can be in generating large volumes of primary clastic deposits, a process that, by reducing the proportion of erupted lava stored in the summit region, will reduce the likelihood of large hazardous pyroclastic flows.
Journal of Geophysical Research | 2015
Alejandro Díaz-Moreno; Jesús M. Ibáñez; S. De Angelis; Araceli García-Yeguas; J. Prudencio; J. Morales; Tiziana Tuvè; Luz García
In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011–2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.
Geological Society, London, Memoirs | 2014
Dario Delle Donne; Maurizio Ripepe; S. De Angelis; Pd Cole; Giorgio Lacanna; Pietro Poggi; R. Stewart
Abstract We show two examples of how integrated analysis of thermal and infrasound signal can be used to obtain, in real time, information on volcanic activity. Soufrière Hills Volcano (SHV) on Montserrat offers the opportunity to study a large variety of processes related to lava-dome activity, such as pyroclastic density currents (PDCs) and large Vulcanian eruptions. Infrasound and thermal analysis are used to constrain the propagation of PDCs and their velocities, which are calculated here to range between 15 and 75 m s−1. During the Vulcanian eruption of 5 February 2010, infrasound and thermal records allow us to identify an approximately 13 s seismic precursor possibly related to the pressurization of the conduit before the explosion onset. The associated very long period (VLP) seismic signal is correlated with the gas-thrust phase detected by thermal imagery, and may reflect a change in the upward momentum induced by the mass discharge. Moreover, from infrasound and thermal analysis, we estimate a gas-thrust phase lasting 22 s, with an initial plume velocity of approximately 170 m s−1 and a mean volumetric discharge rate of 0.3×105–9.2×105 m3 s−1. This information provided in real time gives important input parameters for modelling the tephra dispersal into the atmosphere.
Geophysical Research Letters | 2016
S. De Angelis; Oliver D. Lamb; Anthony Lamur; Adrian J. Hornby; F.W. von Aulock; Gustavo Chigna; Yan Lavallée; Andreas Rietbrock
Abstract The rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound. Here we present results from the inversion of infrasound signals associated with small and moderate gas‐and‐ash explosions at Santiaguito volcano, Guatemala, to retrieve the time history of mass eruption rate at the vent. Acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume. Finally, we combine results from the two methods in order to assess the bulk density of the erupted mixture, constrain the timing of the transition from a momentum‐driven jet to a buoyant plume, and to evaluate the relative volume fractions of ash and gas during the initial thrust phase. Our results demonstrate that eruptive plumes associated with small‐to‐moderate size explosions at Santiaguito only carry minor fractions of ash, suggesting that these events may not involve extensive magma fragmentation in the conduit.
Scientific Reports | 2016
Maurizio Ripepe; G. Barfucci; S. De Angelis; D. Delle Donne; Giorgio Lacanna; Emanuele Marchetti
Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.
Geophysical Journal International | 2012
Jesús M. Ibáñez; S. De Angelis; Alejandro Díaz-Moreno; Pedro A. Hernández; Gerardo Alguacil; Antonio Posadas; Nemesio M. Pérez
Geophysical Research Letters | 2010
Susan C. Loughlin; R. Luckett; G. Ryan; T. Christopher; Vicky Hards; S. De Angelis; Leo Jones; M. Strutt
Nature Geoscience | 2014
Jackie E. Kendrick; Yan Lavallée; Tetsuya Hirose; G. Di Toro; Adrian J. Hornby; S. De Angelis; Donald B. Dingwell
Earth and Planetary Science Letters | 2011
Joachim H Gottsmann; S. De Angelis; Nicolas Fournier; M. Van Camp; Selwyn I. Sacks; Alan T. Linde; Maurizio Ripepe
Journal of Volcanology and Geothermal Research | 2008
Diana C. Roman; S. De Angelis; Joan L. Latchman; Rickie White