Strain accumulation in the southern Alps (NE Italy) and deformation

We use continuous GPS observations to investigate the
rate of strain accumulation in the area affected by the 1976
Friuli earthquakes. Comparison between the motion
predicted by the rigid-rotation of Adria 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 with
very little or no motion transferred to the north.We use elastic
dislocation modelling to investigate the rate of interseismic
loading and the geometry of the shear zone at depth. The
best-fit solution indicates that a northward-dipping creeping
dislocation, whose edge is located within a 50 km wide area
beneath the southern Alps, accomodates 2.1 ± 0.5 mm/yr of
the Adria motion. 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 is consistent with a 20 -dipping dislocation,
locked above 10 km depth and slipping at 2.4 mm/yr,
whose geometry is suggested by seismological informations.