Publication Date:
2019-12-12
Description:
We combine Global Positioning System (GPS) measurements with forward modelling of vis-
coelastic relaxation and after-slip to study the post-seismic deformation of the 1997 Umbria-
Marche (Central Apennines) moderate shallow earthquake sequence. Campaign GPS mea-
surements spanning the time period 1999–2003 are depicting a clear post-seismic deformation
signal. Our results favour a normal faulting rupture model where most of the slip is located
in the lower part of the seismogenic upper crust, consistent with the rupture models obtained
from the inversion of strong motion data. The preferred rheological model, obtained from
viscoelastic relaxation modelling, consists of an elastic upper crust, underlain by a transition
zone with a viscosity of 10 18 Pa s, while the rheology of deeper layers is not relevant for the
observed time-span. Shallow fault creep and after-slip at the base of the seismogenic upper
crust are the first order processes behind the observed post-seismic deformation. The deep
after-slip, below the fault zone at about 8 km depth, acting as a basal shear through localized
time-dependent deformation, identifies a rheological discontinuity decoupling the seismogenic
upper crust from the low-viscosity transition zone.
Description:
Published
Description:
534–546
Description:
4T. Sismicità dell'Italia
Description:
JCR Journal
Keywords:
crustal deformation
;
eathquales
;
GPS
;
rheology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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