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Title: Forecasting unrest and eruption at large volcanic calderas : Campi Flegrei, southern Italy
Author: Steele, Alexander
ISNI:       0000 0004 7660 0942
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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Caldera unrest, characterised by ground uplift and volcano-tectonic (VT) earthquakes, is governed by changes in the magmatic system. Crucial to forecasting the evolution of unrest and the likelihood of eruption is understanding how magma is stored and transported in the shallow crust. The need is particularly important at Campi Flegrei, a populated caldera in southern Italy, because it has had three episodes of unrest since 1950, the first to occur since its last eruption in 1538. Using data from Campi Flegrei, referenced against test data from other volcanoes, this thesis combines a model of elastic-brittle deformation with numerical modelling and statistical techniques to (1) quantify eruption potential in terms of deformation and VT seismicity, and (2) investigate the evolution of stress fields around shallow magma bodies and how they determine critical levels of unrest and preferred eruption locations. The results show that caldera-wide uplift before the 1538 eruption was likely generated by repeated sill intrusion. Eruptions at Campi Flegrei occur when sills interact with the caldera's ring faults, using them as pathways to reach the surface. Thus, an eruption depends on bulk failure (opening) of the ring fault and a sill entering the opened fault. Probabilistic simulations indicate that sills do not often connect with the ring faults, so that several episodes of intrusion and uplift may occur before sill-fault interaction and therefore eruption. An eruption is most likely in the part of the ring fault zone that is closest to the centre of uplift (i.e., sill intrusion). Small shifts in the uplift centre can significantly change which parts of the ring fault favour sill intersection and hence, which areas of the caldera are most at risk to a potential eruption. Bulk failure around pressurising magma bodies tends to occur in crust with high pore-fluid pressures. This has implications for understanding crustal failure at volcanoes and modelling such processes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available