HR: 1340h
AN: G53A-0870    [Abstracts]
TI: Strain accumulation in the area of 1976 Friuli earthquake (Southern Alps, NE Italy) observed by CGPS measurements. Interseimic loading or postseismic effects ?
AU: * D'Agostino, N
EM: dagostin@ingv.it
AF: Ististuto Nazionale Geofisica Vulcanologia, Via Vigna Murata 605, Rome, 00143 Italy
AU: Cheloni, D
EM: cheloni@ingv.it
AF: Ististuto Nazionale Geofisica Vulcanologia, Via Vigna Murata 605, Rome, 00143 Italy
AU: Mantenuto, S
EM: mantenuto@ingv.it
AF: Ististuto Nazionale Geofisica Vulcanologia, Via Vigna Murata 605, Rome, 00143 Italy
AU: Selvaggi, G
EM: selvaggi@ingv.it
AF: Ististuto Nazionale Geofisica Vulcanologia, Via Vigna Murata 605, Rome, 00143 Italy
AU: Michelini, A
G53A-0870 AF: Ististuto Nazionale Geofisica Vulcanologia, Via Vigna Murata 605, Rome, 00143 Italy
AU: Zuliani, D
EM: dzuliani@inogs.it
AF: Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Centro Ricerche Sismologiche, Via Treviso 55, Udine, 33100 Italy
AB: We use continuous GPS observations to investigate the rate of strain accumulation in the area affected by the 1976 Friuli (Italy) earthquakes. Comparison between the motion predicted by the rigid-rotation of the Adriatic block and the shortening observed across the study area, suggests that the {2.0±0.2}mm/yr motion of Adria is entirely absorbed in the Southern Alps through thrusting and crustal thickening. We use elastic dislocation modelling to investigate the rate of interseismic loading and the geometry of the ductile shear zone at depth. The best-fit solution indicates that a northward-dipping dislocation, whose edge is located within a 50 km wide area beneath the Southern Alps, accomodates {2.1±0.5} mm/yr of shortening. Limited resolution on locking depth (acceptable values between 0 and 25 km) and trade-off between dip and slip do not allow a precise reconstruction of the dislocation geometry.The range of acceptable model parameters includes a {20°-dipping dislocation, locked above 10 km depth and slipping at 2.4 mm/yr, whose geometry is indicated by seismological data. At present we do not know what fraction of the deformation is taken up seismically and which faults accommodate the observed shortening on the long-term. In particular, it is not clear whether the observed shortening is taken up only by the faults responsible for the 1976 sequence, or other unknown active faults are involved in the release of the elastic strain loaded by slip at depth. Current research is focused on the geometry of the creeping aseismic shear zone at depth, the comparison with geologic slip rates, and on the role of strain rate variations during the earthquake cycle.
DE: 1209 Tectonic deformation (6924)
DE: 8108 Continental tectonics: compressional
SC: Geodesy [G]
MN: Fall Meeting 2005