13 research outputs found
Coseismic and initial postseismic slip of the 2009 Mw 6.3 l’Aquila earthquake, Italy, from GPS measurements
Here we report the preliminary results of GPS data inversions for coseismic and initial afterslip distributions of the Mw 6.3 2009 April 6 L’Aquila earthquake. Coseismic displacements of continuous and survey-style GPS sites, show that the earthquake ruptured a planar SW-dipping normal fault with ∼0.6 m average slip and an estimated moment of 3.9 × 1018 Nm. Geodetic data agree with the seismological and geological information pointing out the Paganica fault, as the causative structure of the main shock. The position of the hypocentre relative to the coseismic slip distribution supports the seismological evidence of southeastward rupture directivity. These results also point out that the main coseismic asperity probably ended downdip of the Paganica village at a depth of few kilometres in agreement with the small (1–10 cm) observed surface breaks. Time-dependent post-seismic displacements have been modelled with an exponential function. The average value of the estimated characteristic times for near-field sites in the hanging-wall of the fault is 23.9 ± 5.4 d. The comparison between coseismic slip and post-seismic displacements for the first 60 d after the main shock, shows that afterslip occurred at the edges of the main coseismic asperity with a maximum estimated slip of ∼25 cm and an equivalent seismic moment of 6.5 × 1017 Nm. The activation of the Paganica fault, spatially intermediate between the previously recognized main active fault systems, suggests that strain accumulation in the central Apennines may be simultaneously active on distinct parallel fault systems.Published1539–15461.1. TTC - Monitoraggio sismico del territorio nazionale1.9. Rete GPS nazionaleJCR Journalrestricte
Active tectonics of the Adriatic region from GPS and earthquake slip vectors
To investigate the kinematics of the Adriatic region we integrate continuous and
episodic GPS measurements and earthquake slip vectors
selected from the Regional Centroid Moment Tensor (RCMT) catalogue.
Coherent motion of GPS sites in the Po Valley, in Apulia and in the Hyblean Plateau
allows us to estimate geodetically constrained angular velocities for these regions.
The predictions of the GPS-inferred angular velocities are
compared with the earthquake slip vectors, showing that the seismically-expressed
deformation at the microplate boundaries is consistent with the observed geodetic motion.
The remarkable consistency between geodetic, seismological and geological evidence of
active tectonics, suggests that active deformation in the Central Adriatic is controlled
by the relative motion between the Adria and Apulia microplates.
The microplates angular rotation rates are then compared with the rotation rates
calculated with a simple block model supporting the hypotheses (1) that Apulia forms a single
microplate with the Ionian Sea and possibly with the Hyblean region and (2) that
Adria and Apulia rotate in such a way as to accommodate the Eurasia-Nubia relative motion.
We suggest that the present-day microplate configuration follows a recent
fragmentation of the Adriatic promontory that during the Neogene rigidly
transferred the Africa motion to the orogenic belts that now surround the
Adriatic region
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.Publishedreserve
Active tectonics of the Adriatic region from GPS and earthquake slip vectors
To investigate the kinematics of the Adriatic region we integrate continuous and
episodic GPS measurements and earthquake slip vectors
selected from the Regional Centroid Moment Tensor (RCMT) catalogue.
Coherent motion of GPS sites in the Po Valley, in Apulia and in the Hyblean Plateau
allows us to estimate geodetically constrained angular velocities for these regions.
The predictions of the GPS-inferred angular velocities are
compared with the earthquake slip vectors, showing that the seismically-expressed
deformation at the microplate boundaries is consistent with the observed geodetic motion.
The remarkable consistency between geodetic, seismological and geological evidence of
active tectonics, suggests that active deformation in the Central Adriatic is controlled
by the relative motion between the Adria and Apulia microplates.
The microplates angular rotation rates are then compared with the rotation rates
calculated with a simple block model supporting the hypotheses (1) that Apulia forms a single
microplate with the Ionian Sea and possibly with the Hyblean region and (2) that
Adria and Apulia rotate in such a way as to accommodate the Eurasia-Nubia relative motion.
We suggest that the present-day microplate configuration follows a recent
fragmentation of the Adriatic promontory that during the Neogene rigidly
transferred the Africa motion to the orogenic belts that now surround the
Adriatic region.PublishedB124133.2. Tettonica attivaJCR Journalreserve
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
Evidence for localized active extension in the central Apennines (Italy) from global positioning system observations
To assess how contemporary crustal extension is accommodated in the central Apennines, we
use a new continuous and survey-style global positioning system velocity solution and model the velocity field using a bicubic spline interpolation method. The partitioning of contempo- rary deformation over the ~100-km-wide central Apennines belt reveals a pattern of strain accumulation that largely reflects the spatial distribution of historic and recent seismicity. The highest gradients of horizontal velocities are observed across those faults associated with M > 6 historical earthquakes. Dislocation modeling shows that interseismic elastic loading, in which creep occurs below the seismogenic upper crust on the downdip extensions of histori- cally active faults, reproduces the observed velocity gradients. The current resolution level of Quaternary fault slip rates estimates hinders the comparison with past deformation patterns and, in particular, the discrimination between (1) migrating episodes of short-term focused activity, (2) a distributed pattern of simultaneous deformation on parallel fault systems, or (3) long-term localization of active extension. Taking into account geomorphological evidence, we propose that the geodetically observed deformation spatially corresponds with a long-term localization of strain along the long-wavelength (>100 km) topographic bulge caused by its highest gravitation potential energy relative to surrounding lowlands.Published291-2943.2. Tettonica attivaJCR Journalreserve
Evidence for localized active extension in the central Apennines (Italy) from global positioning system observations
To assess how contemporary crustal extension is accommodated in the central Apennines, we
use a new continuous and survey-style global positioning system velocity solution and model the velocity field using a bicubic spline interpolation method. The partitioning of contempo- rary deformation over the ~100-km-wide central Apennines belt reveals a pattern of strain accumulation that largely reflects the spatial distribution of historic and recent seismicity. The highest gradients of horizontal velocities are observed across those faults associated with M > 6 historical earthquakes. Dislocation modeling shows that interseismic elastic loading, in which creep occurs below the seismogenic upper crust on the downdip extensions of histori- cally active faults, reproduces the observed velocity gradients. The current resolution level of Quaternary fault slip rates estimates hinders the comparison with past deformation patterns and, in particular, the discrimination between (1) migrating episodes of short-term focused activity, (2) a distributed pattern of simultaneous deformation on parallel fault systems, or (3) long-term localization of active extension. Taking into account geomorphological evidence, we propose that the geodetically observed deformation spatially corresponds with a long-term localization of strain along the long-wavelength (>100 km) topographic bulge caused by its highest gravitation potential energy relative to surrounding lowlands
Contemporary crustal extension in the Umbria-Marche Apennines from regional CGPS networks and comparison between geodetic and seismic deformation
Here we report the results of the analysis of a GPS velocity field in the Umbria–Marche Apennines (central Italy) obtained from the integration of diverse geodetic networks. The velocity field obtained shows a high
degree of consistency both spatially and in terms of comparison with independent information, despite the limited time span of some GPS stations. Starting from the velocity field we derive a continuous strain rate field applying a spline interpolation technique which provide a smooth estimate of the deformation field. The main feature of the resulting strain rate field is a continuous high (N50 nanostrain/year) strain rate belt coincident with the area of largest historical and instrumental seismic release. The model directions of the
principal axes agree with geological and seismological information indicating NE–SW extension. We transform the strain rate field into geodetic moment rate using the Kostrov formula to evaluate the potential
seismic activity of the region and compare it with actual seismic release in the last 720 years from MwN5.5 earthquakes. This comparison highlights a large possible deficit in the seismic release with respect to the overall potential seismic activity, particularly concentrated in the northern part of the study area. This discrepancy can be resolved with either a large amount of seismicity to be released in the near future or significant aseismic slip and deformation.Published3-122T. Deformazione crostale attivaJCR Journalreserve
Contemporary crustal extension in the Umbria–Marche Apennines from regional CGPS networks and comparison between geodetic and seismic deformation
Here we report the results of the analysis of a GPS velocity field in the Umbria–Marche Apennines (central Italy) obtained from the integration of diverse geodetic networks. The velocity field obtained shows a high
degree of consistency both spatially and in terms of comparison with independent information, despite the limited time span of some GPS stations. Starting from the velocity field we derive a continuous strain rate field applying a spline interpolation technique which provide a smooth estimate of the deformation field. The main feature of the resulting strain rate field is a continuous high (N50 nanostrain/year) strain rate belt coincident with the area of largest historical and instrumental seismic release. The model directions of the
principal axes agree with geological and seismological information indicating NE–SW extension. We transform the strain rate field into geodetic moment rate using the Kostrov formula to evaluate the potential
seismic activity of the region and compare it with actual seismic release in the last 720 years from MwN5.5 earthquakes. This comparison highlights a large possible deficit in the seismic release with respect to the overall potential seismic activity, particularly concentrated in the northern part of the study area. This discrepancy can be resolved with either a large amount of seismicity to be released in the near future or significant aseismic slip and deformation.Published3-122T. Deformazione crostale attivaJCR Journalreserve
Coseismic and initial postseismic slip of the 2009 Mw 6.3 l’Aquila earthquake, Italy, from GPS measurements
Here we report the preliminary results of GPS data inversions for coseismic and initial afterslip distributions of the Mw 6.3 2009 April 6 L’Aquila earthquake. Coseismic displacements of continuous and survey-style GPS sites, show that the earthquake ruptured a planar SW-dipping normal fault with ∼0.6 m average slip and an estimated moment of 3.9 × 1018 Nm. Geodetic data agree with the seismological and geological information pointing out the Paganica fault, as the causative structure of the main shock. The position of the hypocentre relative to the coseismic slip distribution supports the seismological evidence of southeastward rupture directivity. These results also point out that the main coseismic asperity probably ended downdip of the Paganica village at a depth of few kilometres in agreement with the small (1–10 cm) observed surface breaks. Time-dependent post-seismic displacements have been modelled with an exponential function. The average value of the estimated characteristic times for near-field sites in the hanging-wall of the fault is 23.9 ± 5.4 d. The comparison between coseismic slip and post-seismic displacements for the first 60 d after the main shock, shows that afterslip occurred at the edges of the main coseismic asperity with a maximum estimated slip of ∼25 cm and an equivalent seismic moment of 6.5 × 1017 Nm. The activation of the Paganica fault, spatially intermediate between the previously recognized main active fault systems, suggests that strain accumulation in the central Apennines may be simultaneously active on distinct parallel fault systems