Shear wave splitting in southern tyrrhenian subduction zone (Italy) from CESIS and CAT/SCAN projects

In the years 2003 -2006 several broad band stations were installed in Southern Italy: 15 permanent ones (CESIS project), improved the INGV Italian national network and 40 temporary ones were installed in the frame of CAT/SCAN NSF project.We present shear wave splitting measurements obtained analyzing SKS phases and local S phases from slab earthquakes. We used the method of Silver & Chan to obtain shear wave splitting parameters: fast direction and delay time. Shear wave splitting measurements reveals strong seismic anisotropy in the mantle beneath Southern Tyrrhenian subduction system. The SKS splitting results show fast polarization directions varying from NNW-SSE in the Southern Apennines to N-S and to E-SW in Calabria, following the strike of the mountain chain. Moving toward the Adriatic sea the fast directions rotate from N-S to NE-SW. Fast directions could indicate the mantle flow below the slab, due to its retrograde motion but also the lithospheric fabric of the subducting plate. In the Tyrrhenian domain, above the slab, from Sardinia to the Italian and Sicilian coasts the dominant fast direction is E-W and could be related to the opening of the Tyrrhenian basin and to the corner flow in the asthenospheric wedge. In Sicily fast directions depict a ring around the slab edge supporting the existence of a slab tear and of a return flow from the back to the front of the slab. Measurements obtained with intermediate and deep earthquakes slab S phases show an extremely complex pattern of fast directions. They are mostly distributed in front of the Tyrrhenian Calabrian coast in correspondence of the fast velocity anomaly imaged at 150 km depth by tomography. We can relate this fast directions variability to the complex structure of the slab itself. The complex pattern of SKS and S splitting measurements suggests the presence of local scale mantle flow controled by the motion of an anisotropic slab

SKS splittings in the southern Apennines-Calabrian arc region (southern Italy)

During the years 2003-2006 CAT/SCAN (Calbarian-Apennine-TyrrhenianlSubductionCollision- Accretion Network) temporary broadband stations operate in Southern Apennine and Calabria (Italy). In the same period CESIS-INGV project improved the number of permanent seismic stations in the same area. We analyze the data recorded to study seismic anisotropy and to investigate the mantle flow in the boun(fary-zoile{ between Southern Apennine and Calabriaibeneath and above the subducting slab. In the current work we present new shear wave splittings obtained analyzing SKS phases of 15 teleseisms with epicentral distance ranging from 88.40 to 98.20 and magnitude greater than 6.0. We used the method of Silver & Chan (1991) to obtained anisotropic parameters: delay time and fast polarization direction. The splitting parameters reveal strong seismic anisotropy in the mantle beneath Southern Tyrrhenian Sea- Calabrian Arc System that seems to be controlled by the slab presence. The clear variability in the fast directions allow us to hypothesize the existence of different anisotropic domains: fast polarization directions vary from NNW -SSE in the tyrrhenian side ofthe Southern Apennine to N-S and NE-SW toward the Adriatic Sea. Moving toward the Calabria fast directions are prevalently trench parallel showing a NE-SW orientation following the strike on the mountain chain

Crustal Structure in the Southern Apennines from Teleseismic Receiver Functions

While the upper structure of the Southern Apennines is known, lack of control on the deep structure allows competing thin-skin and tick-skin models of the orogen. In thin-skin models the detachment decouples a stack of rootless nappes from the basement. In the tick-skin models, besement is involved in the most recent phase of thrusting. To examine crustal structure, we use teleseismic data from the CAT/SCAN array in southern Italy. We use receiver functions (RF) processed into a Common Conversion Point (CCP) stack to generate images of the crust. Interpretation and correlation to geological structure is 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 tick-skin interpretation. In a thick-skin reconstruction, the amount of shortening is much smaller than for a thin-skin model. This implies considerably less Plio-Pleistocene shortening across the Apennines and suggests an E-SE motion of the Calabrian Arc subparallel to the southern Apennines rather than a radial expansion of the Arc

Illumination of the Crustal Structure in the Southern Apennines using Teleseismic Receiver Functions, CAT/SCAN Project

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

Results from the seismological component of CAT/SCAN, the Calabria-Apennine Tyrrhenian/Subduction-Collision-Accretion-Network

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.Published7922T. Tettonica attivaN/A or not JCRrestricte

Sequence-Specific Binding of Recombinant Zbed4 to DNA: Insights into Zbed4 Participation in Gene Transcription and Its Association with Other Proteins

Zbed4, a member of the BED subclass of Zinc-finger proteins, is expressed in cone photoreceptors and glial Müller cells of human retina whereas it is only present in Müller cells of mouse retina. To characterize structural and functional properties of Zbed4, enough amounts of purified protein were needed. Thus, recombinant Zbed4 was expressed in E. coli and its refolding conditions optimized for the production of homogenous and functionally active protein. Zbed4’s secondary structure, determined by circular dichroism spectroscopy, showed that this protein contains 32% α-helices, 18% β-sheets, 20% turns and 30% unordered structures. CASTing was used to identify the target sites of Zbed4 in DNA. The majority of the DNA fragments obtained contained poly-Gs and some of them had, in addition, the core signature of GC boxes; a few clones had only GC-boxes. With electrophoretic mobility shift assays we demonstrated that Zbed4 binds both not only to DNA and but also to RNA oligonucleotides with very high affinity, interacting with poly-G tracts that have a minimum of 5 Gs; its binding to and GC-box consensus sequences. However, the latter binding depends on the GC-box flanking nucleotides. We also found that Zbed4 interacts in Y79 retinoblastoma cells with nuclear and cytoplasmic proteins Scaffold Attachment Factor B1 (SAFB1), estrogen receptor alpha (ERα), and cellular myosin 9 (MYH9), as shown with immunoprecipitation and mass spectrometry studies as well as gel overlay assays. In addition, immunostaining corroborated the co-localization of Zbed4 with these proteins. Most importantly, in vitro experiments using constructs containing promoters of genes directing expression of the luciferase gene, showed that Zbed4 transactivates the transcription of those promoters with poly-G tracts