Publication Date:
2017-04-04
Description:
The 1982-84 unrest episode at Campi Flegrei (CF) caldera, Italy, was
characterized by huge deformation (more than 1.5 m uplift) concentrated inside
the caldera. According to point source isotropic models in homogeneous
elastic and visco-elastic half-spaces, the source depth is very shallow (about
3 km). If the source radius is about 1 km this implies that magma is at a
depth of 2 km depth. However, several independent observations show that
the top of the magma chamber at CF must be deeper than 4 km. This paper
investigates how the inferred source depth increases when rigidity
heterogeneities (obtained through seismic tomography at CF) are considered and
when the long-term deformation takes place under drained conditions. Finite
element models indicate that overpressure needed at the source to reproduce
the 1.5 m maximum uplift is however beyond typical rock strength values. This
evidence, together with the high thermal anomalies, the presence of fluids and
the low cohesion of tuffs filling the caldera, suggests the use of
elastoplastic constitutive laws. For elastoplastic behavior, the same
deformation is obtained using a deeper source (with center at 5 km
depth) and a lower overpressure (than required by elastic models). The plastic
deformation concentrates both at the source boundaries and above the source,
where seismic activity has been recorded. These results indicate that the
rheological properties of the shallow crust of CF have important implications
for hazard estimate during unrest episodes.
Description:
INGV-Gruppo Nazionale per la Vulcanologia; Ministero dell'Istruzione Università e Ricerca- FIRB Project
Description:
Published
Description:
14
Description:
reserved
Keywords:
finite element modelling
;
Campi Flegrei
;
surface deformation
;
plasticity
;
rheological layering
;
overpressure source
;
04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
330510 bytes
Format:
application/pdf
