SKS splitting in Southern Italy: anisotropy variations in a fragmented subduction zone.

In this paper we present a collection of good quality shear wave splitting measurements in Southern Italy. In addition to a large amount of previous splitting measurements, we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the CAT/SCAN temporary network. These new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the Apulian Platform. For our analysis we have selected wellrecorded SKS phases and we have used the method of Silver and Chan to obtain the splitting parameters: the azimuth of the fast polarized shear wave (φ) and delay time (δt). Shear wave splitting results reveal the presence of a strong seismic anisotropy in the subduction system below the region. Three different geological and geodynamic regions are characterized by different anisotropic parameters. The Calabrian Arc domain has fast directions oriented NNE–SSW and the Southern Apennines domain has fast directions oriented NNW–SSE. This rotation of fast axes, following the arcuate shape of the slab, is marked by a lack of resolved measurements which occurs at the transition zone between those two domains. The third domain is identified in the Apulian Platform: here fast directions are oriented almost N–S in the northern part and NNE–SSW to ENE–WSW in the southern one. The large number of splitting parameters evaluated for events coming from different back-azimuth allows us to hypothesize the presence of a depth-dependent anisotropic structure which should be more complicated than a simple 2 layer model below the Southern Apennines and the Calabrian Arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer, at least at the edge of Southern Apennines and Apulian Platform. We interpret the variability in fast directions as related to the fragmented subduction system in the mantle of this region. The trench-parallel φ observed in Calabrian Arc and in Southern Apennines has its main source in the asthenospheric flow below the slab likely due to the pressure induced by the retrograde motion of the slab itself. The pattern of φ in the Apulian Platform does not appear to be the direct result of the rollback motion of the slab, whose influence is limited to about 100 km from the slab. The anisotropy in the Apulian Platform may be related to an asthenospheric flow deflected by the complicated structure of the Adriatic microplate or may also be explained as frozen-in lithospheric anisotropy

Integrated SEED data archive for temporary seismic experiments

One of the most valuable results achieved during the work on S5 project is the implementation of a new temporary network data management that allows the integration in the National Data Center together with all other seismological data produced by INGV. This makes all data gathered during temporary experiments immediately available from the same source and in the same data format (SEED) increasing the availability for processing and analysis. Moreover the data are distributed to the scientific community using the EIDA (European Integrated Data Archive http://eida.rm.ingv.it/). The first application has been carried out for the Messina 1908-2008 experiment (WP2.2) http://dpc-s5.rm.ingv.it/en/Database-MessinaFault.html where has been achieved the complete integration of permanent networks (National Seismic Network, MedNet and Peloritani Local Network), temporary deployments (INGV-CNT and INGVCT mobile networks) and OBS data. All the procedures were used and further improved during the L'Aquila sequence (Task 4) where data was available for processing together with permanent network data as soon as it was gathered from the field giving to the scientific community the opportunity to study the evolution of the seismic sequence with higher density of stations (WP4.2) ( h t t p : / / d p c - s 5 . r m . i n g v . i t / e n / D a t a b a s e - AquilaFaultSystem.html).UnpublishedSede Ispra | Via Curtatone 7, Roma1.1. TTC - Monitoraggio sismico del territorio nazionaleope

Lateral Changes of seismic anisotropy in the upper mantle around the Northern Apennines

We performed three-dimensional analysis of anisotropic parameters of body waves to develop a 3D self-consistent dynamic model of the syn-convergent extension in the Northern Apennines within the multidisciplinary project RETREAT. Simultaneous extension within the convergent margin can be the consequence of the retreat of the subducting Adriatic plate from the orogenic front, caused by sub-lithosphere mantle processes that seismic anisotropy can help to decipher. We use data recorded by the RETREAT temporary array consisting of 35 stations complemented by data of permanent INGV observatories. Currently, 18-months of data are available from some stations, representing half of the passive experiment duration. We detect many examples of core-refracted shear-wave splitting within the upper mantle, and observe both distinct lateral variations of anisotropic parameters and their dependence on the direction of propagation. In particular, the fast shear-wave polarization changes from slab-perpendicular to slab-parallel along the Apennines chain. There is also a distinct change in the anisotropic signals across the presumed boundary of the Tyrrhenian and Adriatic micro-plates. Variations of the splitting time delays and orientation of the fast shear waves, together with considerations on the geodynamics of the area, seem to exclude simple sub-lithosphere mantle corner flow as the only source of the observed anisotropy. Alternate models include (1) a frozen-in fabric of different lithosphere domains, and (2) complex mantle flow associated with the Plio-Pleisocene uplift and extension of Tuscany

Imaging the three-dimensional architecture of the Middle Aterno basin (2009 L’ Aquila earthquake, Central Italy) using ground TDEM and seismic noise surveys: preliminary results

We present preliminary results from a multidisciplinary geophysical approach ap- plied to the imaging of the three-dimensional architecture of the Middle Aterno basin, close to the epicentral area of the 2009 L’Aquila earthquake (central Italy). We collected several time domain electromagnetic soundings (TDEM) coupled with seismic noise measurements focu- sing on the characterization of the bedrock/in ll interface. Our preliminary results agree with existing geophysical data collected in the area, and show that the southeastern portion of the basin is characterized by a deepening of the Mesozoic-Tertiary bedrock down to a depth of more than 450 m. We found that a joint use of electromagnetic and seismic methods signi - cantly contributes in obtaining new insights on the 3D geometry of the Middle Aterno basin. Moreover, we believe that our combined approach based on TDEM and noise measurements can be adopted to investigate similar geological settings elsewhere.PublishedPescina (AQ), Italy2T. Tettonica attiva3T. Pericolosità sismica e contributo alla definizione del rischio7A. Geofisica di esplorazioneope

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

Geometry and evolution of a fault-controlled Quaternary basin by means of TDEM and single-station ambient vibration surveys: The example of the 2009 L'Aquila earthquake area, central Italy

We applied a joint survey approach integrating time domain electromagnetic soundings and single-station ambient vibration surveys in the Middle Aterno Valley (MAV), an intermontane basin in central Italy and the locus of the 2009 L’Aquila earthquake. By imaging the buried interface between the infilling deposits and the top of the pre-Quaternary bedrock, we reveal the 3-D basin geometry and gain insights into the long-term basin evolution. We reconstruct a complex subsurface architecture, characterized by three main depocenters separated by thresholds. Basin infill thickness varies from ~200–300m in the north to more than 450m to the southeast. Our subsurface model indicates a strong structural control on the architecture of the basin and highlights that the MAV experienced considerable modifications in its configuration over time. The buried shape of the MAV suggests a recent and still ongoing predominant tectonic control by the NW-SE trending Paganica-San Demetrio Fault System (PSDFS), which crosscuts older ~ENE and NNE trending extensional faults. Furthermore, we postulate that the present-day arrangement of the PSDFS is the result of the linkage of two previously isolated fault segments. We provide constraints on the location of the southeastern boundary of the PSDFS, defining an overall ~19 km long fault system characterized by a considerable seismogenetic potential and a maximum expected magnitude larger than M6.5. This study emphasizes the benefit of combining two easily deployable geophysical methods for reconstructing the 3-D geometry of a tectonically controlled basin. Our joint approach provided us with a consistent match between these two independent estimations of the basin substratum depth within 15%.Published2236–22597T. Struttura della Terra e geodinamica2TR. Ricostruzione e modellazione della struttura crostaleJCR Journa

The subduction structure of the Northern Apennines: results from the RETREAT seismic deployment

The project Retreating-trench, extension, and accretion tectonics, RETREAT, is a multidisciplinary study of the Northern Apennines (earth.geology.yale.edu/RETREAT/), funded by the United States National Science Foundation (NSF) in collaboration with the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Grant Agency of the Czech Academy of Sciences (GAAV). The main goal of RETREAT is to develop a self-consistent dynamic model of syn-convergent extension, using the Northern Apennines as a natural laboratory. In the context of this project a passive seismological experiment was deployed in the fall of 2003 for a period of three years. RETREAT seismologists aim to develop a comprehensive understanding of the deep structure beneath the Northern Apennines, with particular attention on inferring likely patterns of mantle flow. Specific objectives of the project are the crustal and lithospheric thicknesses, the location and geometry of the Adriatic slab, and the distribution of seismic anisotropy laterally and vertically in the lithosphere and asthenosphere. The project is collecting teleseismic and regional earthquake data for 3 years. This contribution describes the RETREAT seismic deployment and reports on key results from the first year of the deployment. We confirm some prior findings regarding the seismic structure of Central Italy, but our observations also highlight the complexity of the Northern Apennines subduction system

“Messina 1908-2008”: Progetto di ricerca integrato per l’area Calabro - Peloritana. L’esperimento di sismica passiva

Il 28 dicembre 1908 un forte terremoto colpì duramente le città di Messina e di Regg io Calabria e molteplici centri abitati limitrofi. L’evento sismico di Mw=7.1 generò un maremoto e causò circa 100.000 morti. Durante il 2008 numerose sono state le iniziative per rievocare tale importante terremoto che è ricordato nella storia come il più forte avvenuto in Italia. Tra le iniziative promosse dall’Istituto Nazionale di Geofisica e Vulcanologia vi è il progetto di ricerca “Messina 1908-2008” le cui finalità sono far convergere i dati sismici e geodetici g ià a disposizione dei singoli gruppi di ricerca in un’unica banca dati e nel contempo promuoverne l’acquisizione di nuovi. In questo rapporto è descritto l’esperimento di sismica passiva integrato mare-terra iniziato ad ottobre 2007 e ter minato nel gennaio 2010 avente l’obiettivo di acquisire nuovi dati di alta qualità e dettaglio per ottenere una migliore definizione della microsismicità locale. Ciò consentirà di raggiungere una migliore comprensione di come inter ag iscano il processo di subduzione e le dinamiche superficiali nell’area dell’arco Calabro Peloritano ed in particolare nello stretto di Messina

Notulae to the Italian alien vascular flora: 16

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records and status changes from casual to naturalized for Italy or for Italian administrative regions. Nomenclatural and distribution updates, published elsewhere, and corrections are provided as supplementary material