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Title: Ground deformation at Campi Flegrei, southern Italy : an indicator for the magmatic feeding system
Author: Woo, Y. L. J.
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2007
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Abstract:
This thesis has used patterns of ground deformation since Roman times to develop new models of the magmatic system beneath Campi Flegrei, an active caldera to the west of Naples in Southern Italy. New data have been obtained from historical and archaeological records, as well as from reanalyses of measurements obtained during the volcano-seismic crises of 1968-72 and 1982-84. The results show that deformation has occurred against a background rate of caldera subsidence of about 17 mm yr1. This subsidence has been interrupted by extended episodes of net uplift in 540-800, 1430-1538 and since 1968, which produced maximum uplifts of approximately 15, 17 and (to date) 3 m. New modelling of the post-1968 deformation, which was concentrated between 1968-72 and 1982-84, suggests that each uplift was driven by the emplacement of radiaUy-symmetric sills at depths of 2.5-2.75 km, near the contact between basement rock and overlying volcanic deposits. The sills have radii between 1.56 and 2.75 km and volumes of 0.02 km3. Heating of aquifers produced temporary additional uplifts of some 0.2-0.5 m, but these decayed following the outflow of water. Extrapolation of the results suggests that each of the preceding episodes of extended uplift involved the intrusion of about 10 sills. Such behaviour is consistent with the sills having been fed from a reservoir of tens of km3 at a depth of about 15 km, near the base of the upper elastic crust. This reservoir has itself been supplied from a source about ten times larger and at a depth of about 30 km. During the post-1968 crises, the deformation due to sill emplacement was supplemented by an additional WNW-ESE horizontal extension at a strain rate of about 2.7 x 10_ 5 yr1. The additional deformation is consistent with the elastic upper crust being dragged apart during visco-elastic relaxation of the lower crust, with an inferred viscosity of 6 x 1018 Pa s. The preferred direction of relaxation may reflect different rates of regional NE-SW extension to the north and south of Campi Flegrei. If the current unrest follows previous extended episodes, uplift may continue for another 80-90 years and produce a further net uplift of some 12-14 m. The 21st Century is thus expected to represent a period of elevated volcano-seismic hazard in Campi Flegrei.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.644407  DOI: Not available
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