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| Titel |
Role of asymmetric deformation sources in volcanic areas |
| VerfasserIn |
Claudio Ferrari, Maurizio Bonafede |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039705
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| Zusammenfassung |
| Ground deformation and gravity changes in volcanic areas are the result of the action of deep
structures and the inversion of these data may be used to infer the nature and the
main features of these deformation sources. Triaxial ellipsoids (Davis, 1986) and
circular horizontal cracks (Fialko, 2001) are generally employed in these inversions,
but they do not represent the most general type of internal sources, since they can
generate only a limited subset of moment tensors. Using dislocation theory and the
boundary element technique, we present two alternative models of deformation
sources: the first type is represented by pressurized parallelepiped cavities, while
the second type by dipping elliptical cracks. We show that parallelepiped cavities
extend slightly the set of moment tensors associated to ellipsoidal cavities, while
dipping elliptical cracks can be useful when asymmetries are present in the surface
deformation field. Furthermore, both models are able to take into account the release of a
deviatoric stress field which instead cannot be present on the boundaries of a pressurized
fluid filled cavity. The discretization order of the sources can be suitably selected
according to the following considerations. To obtain the ratios between axes and the
orientation of the source, a low order decomposition can be used in the boundary element
procedure since the ratio uz-ur on the surface is approximately independent from the
discretization order. Once the optimal parameters for the models are obtained, the
discretization order can be increased in order to infer the depth and the size of the
deformation source. We study also the possibility that shear dislocations take place on the
boundary of a pressurized source when its geometry is not planar or when it is close to
the free surface. The models proposed will be applied to study the deformation
field associated to the 1982-84 unrest episode at Campi Flegrei caldera (Italy). |
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