Publication Date:
2017-04-04
Description:
We consider the space–time distribution of seismicity during the 1982–1984 unrest at Campi Flegrei caldera
(Italy) where a correlation between seismicity and rate of ground uplift was suggested. In order to investigate
this effect, we present a model based on stress transfer from the deformation source responsible for the unrest
to potential faults. We compute static stress changes caused by an inflating source in a layered half-space.
Stress changes are evaluated on optimally oriented planes for shear failure, assuming a regional stress with
horizontal extensional axis trending NNE-SSW. The inflating source is modeled as inferred by previous studies
from inversion of geodetic data with the same crustal model here assumed. The magnitude of the regional
stress is constrained by imposing an initial condition of “close to failure” to potential faults. The resulting
spatial distribution of stress changes is in agreement with observations. We assume that the temporal
evolution of ground displacement, observed by a tide-gauge at Pozzuoli, was due mainly to time dependent
processes occurring at the inflating source. We approximate this time dependence in piecewise-linear way
and we attribute it to each component of average stress-change in the region interested by the observed
seismicity. Then we evaluate the effect of a time dependent stressing rate on seismicity, by following the
approach indicated by Dieterich (1994) on the basis of the rate- and state-dependent rheology of faults. The
seismicity rate history resulting from our model is in general agreement with data during the period 1982–
1984 for reasonable values of unconstrained model-parameters, the initial value of the direct effect of friction
and the reference shear stressing rate. In particular, this application shows that a decreasing stressing-rate is
effective in damping the seismicity rate.
Description:
Published
Description:
287-298
Description:
3.6. Fisica del vulcanismo
Description:
JCR Journal
Description:
reserved
Keywords:
Triggered seismicity
;
Volcanic tremor
;
04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
