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Seeber, L.
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- PublicationOpen AccessIllumination of the Crustal Structure in the Southern Apennines using Teleseismic Receiver Functions, CAT/SCAN Project(2006)
; ; ; ; ; ; ; ;Steckler, M. S.; Lamont-Doherty Earth Observatory of Columbia University ;Wilson, C. K.; Lamont-Doherty Earth Observatory of Columbia University ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Seeber, L.; Lamont-Doherty Earth Observatory of Columbia University ;Amato, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Lerner-Lam, A.; Lamont-Doherty Earth Observatory of Columbia University; ; ; ; ; ; Field geology, well data and seismic imaging have illuminated the upper crustal structure of the Southern Apennines. However, lack of control of the deep structure allows viable competing thin-skin and thick-skin models of the orogen. In thin-skin models the detachment decouples a stack of rootless nappes from the basement. In thick-skin models, basement is involved in the most recent phase of thrusting. To examine the deep crustal structure, we use the teleseismic recordings from the CAT/SCAN array, deployed in southern Italy from Dec. 2003-Oct. 2005. We use receiver functions processed into a Common Conversion Point stack to generate images of the crust. We image three main westward-dipping seismic-velocity discontinuities where P-to-S conversions occur. They correspond to velocity jumps at the Moho, the upper-lower crust boundary and sedimentary interfaces resulting from the contrast between clastic and carbonate strata with basement. The CCP image matches features from both thin-skin and thick skin model. The lateral continuity of the converters favors thin skin, but consistent interpretation across the image favors the thick skin. Overall, the results provide a better fit to the thick-skin interpretation. This suggests a change in structural style as the collision with Apulia halted motion. This model also implies considerably less Plio-Pleistocene shortening across the Apennines and a SE motion of the Calabrian Arc subparallel to the southern Apennines rather than a radial expansion of the Arc.177 78 - PublicationRestrictedForearc extension and slow rollback of the Calabrian Arc from GPS measurements(2011)
; ; ; ; ; ; ; ;D'Agostino, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;D'Anastasio, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Gervasi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Guerra, I.; Dipartimento di Fisica, Università della Calabria ;Nedimovic, M. R.; Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, Canada. ;Seeber, L.; Lamont-Doherty Earth Observatory, The Earth Institute at Columbia University, Palisades, New York, USA. ;Steckler, M.; Lamont-Doherty Earth Observatory, The Earth Institute at Columbia University, Palisades, New York, USA.; ; ; ; ; ; Here we describe the horizontal velocities of continuous GPS stations in the Calabrian Arc (CA) and surrounding regions. The appropriate reference frame to evaluate the crustal motion of the CA is considered by assessing the internal deformation and the relative motion of the crustal blocks in the foreland of the Apennines␣Ionian␣Maghrebides subduction system. We propose that the motion of CA rela- tive to the subducting Ionian lower plate is most properly assessed by minimizing the GPS velocities in Apulia. In this reference frame the significant ␣2 mm/yr southeast- ward motion of the stations on the Ionian flank of the CA shows that the arc is still moving towards the trench in agreement with the observations of active shortening in the Ioanian wedge. This southeastward migration is associated to 1.4 ± 0.3 mm/yr E␣W extension of the forearc in northern Calabria, comparable with the seismic strain averaged in the last 500 years. The limited subaerial exposure decreases the resolution on locking of the subduction interface but the distribution and direction of crustal extension along the CA impose important constraints on geodynamic interpreta- tions of the area.250 46 - PublicationRestrictedResults from the seismological component of CAT/SCAN, the Calabria-Apennine Tyrrhenian/Subduction-Collision-Accretion-Network(2012)
; ; ; ; ; ; ; ; ; ; ; ; ;Steckler, M. S.; Columbia University ;Guerra, I.; Università della Calabria ;Amato, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Armbruster, J.; Columbia University ;Baccheschi, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Di Luccio, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Gervasi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Gu, Y. J.; University of Alberta Canada ;Lerner-Lam, L.; Columbia University ;Matgheriti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Piana Agostinetti, N.; Dublin Institute for Advanced Studies Geophysics Section, Dublin 2 Ireland ;Seeber, L.; Columbia University; ; ; ; ; ; ; ; ; ; ; The Calabrian Arc is the final remnant of a Western Mediterranean microplate driven by rollback. The Calabrian-Apennine-Tyrrhenian/Subduction-Collision-Accretion Seismic Network (CAT/SCAN) was a passive seismic experiment to study of the Calabrian Arc and its transition to the southern Apennines. The follow up Calabrian Arc project added a multidisciplinary (seismology, geology, geomorphology, geochronology, GPS, etc.) approach to better understand the tectonics of southern Italy imaged by the CAT/SCAN experiment. Here we focus on the seismological results of the two projects. The CAT/SCAN land deployment consisted of three phases. The initial phase included an array of 39 broadband seismometers onshore, deployed during the winter of 2003/4. In September 2004, the array was reduced and in April 2005, the array was reduced once again. The field deployment was completed in October 2005. Offshore, 12 broadband Ocean Bottom Seismometers (OBSs) were deployed in the beginning of October 2004. However, only 1 was recovered normally while several others were recovered after being disturbed by trawling. The experiment goal was to determine the structure of the Calabrian subduction and southern Apennine collision systems and the structure of the transition from oceanic subduction in Calabria to continental collision in the southern Apennines.425 38 - PublicationRestrictedCrustal structure in the Southern Apennines from teleseismic receiver functions(2008-02)
; ; ; ; ; ; ; ;Steckler, M. S.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Wilson, C. K.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Seeber, L.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York ;Amato, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Lerner-Lam, A.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York; ; ; ; ; ; While the upper crustal structure of the Southern Apennines is known, lack of control on the deep structure allows competing thin-skinned and thick-skinned models of the orogen. In thin-skinned models, the detachment decouples a stack of rootless nappes from the basement. In thick-skinned models, basement is involved in the most recent phase of thrusting. To examine crustal structure, we use teleseismic data from the Calabria-Apennine-Tyrrhenian/Subduction- Accretion-Collision Network (CAT/SCAN) array in southern Italy. We use receiver functions (RF) processed into a common conversion point stack to generate images of the crust. Inter- pretation and correlation to geological structure are done using inversions of individual station RFs. We focus on a shallow discontinuity where P-to-S conversions occur. In the foreland, it corresponds to velocity jumps between carbonate and clastic strata with basement. A similar interpretation for the Apennines provides the most parsimonious explanation and supports a thick-skinned interpretation. In a thick-skinned reconstruction, the amount of shortening is much smaller than for a thin-skinned model. This implies considerably less Pliocene–Pleistocene shortening across the Apennines and suggests an east-southeast motion of the Calabrian arc subparallel to the southern Apennines rather than a radial expansion of the arc.595 102 - PublicationRestrictedAn Intense Earthquake Swarm in the Southernmost Apennines: Fault Architecture from High-Resolution Hypocenters and Focal MechanismsBetween 2010 and 2013, the Pollino Mountains region (south Italy), already proposed as a seismic gap, was affected by a seismic crisis of more than 5000 small-to-moderate earthquakes (maximum magnitude ML 5.0). Preliminary analyses performed in a previous work highlighted that this activity can be ascribed to normal faulting on north-northwest-trending west-dipping dislocation surfaces consistent with the general seismotectonic frame of the southern Apennines. This work contributes additional data and a more sophisticated analyses that highlight new features of the seismic swarm and support a new interpretation for the study area. We obtained high-precision locations and focal mechanisms using the double-difference method and the cut-and-paste waveform inversion method, respectively. The 3D patterns of hypocenters and focal mechanisms consistently image an ∼10-km-long north-northwest-striking and west-dipping fault zone between 5 and 10 km depth, with predominantly extensional kinematics. The high-resolution data show that this zone broadens from north to south as a result of secondary faulting. The depicted geometry, with preliminary geological observation, leads to the hypothesis of multiple seismogenic normal faults rooted into more regional shallow-dipping detachments inherited from the pre-existing Apennine thrust tectonics.
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