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  • 1
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    Reference seismic velocity Earth model for Italy from local source tomography and 30 years of controlled source seismology data (2012)
    Details
    Publication Date: 2020-10-26
    Description: We present here a new high resolution regional P-wave velocity model for the lithosphere beneath the Italian region obtained by including information on the Moho topography, and integrating results from local earthquake tomography with 30 years of CSS data, applying the method of Waldhauser (1996). For the 3D moho map, we extended the crustal model, already available for the Alps by Lippitsch et al., 2003, to the Italian peninsula, Corsica, Sardinia, and Sicily. The tomographic model is obtained by inverting 166,000 Pg and Pn arrival times large part of which have been automatically picked and consistently weighted with an advanced automatic picking system (Aldersons, 2004). The resolution of the obtained velocity model is consistently higher and the grid spacing consistently smaller than in previous tomographic works targeting the same region. We are able to image the complex geometry of this part of the subduction-collision system between the Eurasian and African plates adding important details to the overview derived by the teleseismic tomography. Our results clearly show the plate boundary at Moho level from the Alps to the Southern Apennines and the Calabrian Arc in a volume unresolved in previous studies. The use of global 1D velocity models based on the flat Earth assumption is a pre-requisite to refine and interpret images and seismic responses of the earth obtained with geophysical studies (P and S tomography, surface wave tomography etc). Our model is suitable as a good starting point for a 3D velocity reference model of the crust and upper mantle beneath the Mediterranean area to be extended to the Adriatic Sea and to the Ionian Sea, with benefit for earthquakes location,teleseismic tomography, focal mechanisms and CMT
    Description: Published
    Description: Vienna
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: local earthquake tomography ; velocity model ; Italian Peninsula ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 2
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    Seismic anisotropy and subduction in Southern Italy (2012)
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    Publication Date: 2017-04-04
    Description: In the current work we present a large collection of shear wave splitting measurements in the Calabrian Arc-Tyrrhenian basin subduction system. For our analysis we used earthquakes recorded from 2003 to 2005 at the CAT/SCAN temporary network and at the INGV national network. The dataset consists of SKS teleseismic phases (earthquakes with delta 87° - 112° and magnitude greater than 6.0) and of local S phases (events deeper than 150 km). We used the method of Silver and Chan to obtain the splitting parameters: fast direction (φ) and delay time (δt). Shear wave splitting results reveal the presence of a strong seismic anisotropy with a complex pattern of fast directions in the subduction system below the region. The SKS fast polarization directions define three anisotropic domains which correspond to the three different geological and geodynamic regions: the Calabrian Arc domain with fast directions oriented NNE-SSW;the Southern Apennines domain with fast directions oriented NNW-SSE and the Apulian Platform domain with fast directions oriented almost N-S in the northern part and ENE-WSW in the southern. The large number of splitting parameters evaluated for events coming from different back-azimuth allow us to hypothesize the presence of a depth dependence anisotropic structure in each of the identified domains and to constrain at 50 km depth the upper limit of the anisotropic layer. We interpret the trench-parallel φ observed in Calabrian Arc and in Southern Apennines as a mantle flow below the slab, likely due to the pressure induced by the retrograde motion of the slab itself. The pattern of trench perpendicular φ in the Apulian Platform seems to be not a direct result of the roll-back motion of the slab and may be explained as frozen-in lithospheric anisotropy or as asthenospheric flow deflected by the complicated structure of the Adriatic microplate. Results obtained with S phases show an extremely complex pattern of fast directions and delay times. These last measures are mainly located in the south-eastern sector of the Tyrrhenian Sea in correspondence of the high velocity body imaged at 150 km depth by the tomography. We related this strong fast directions variability inside the slab to the complex structure of the slab itself. The variable pattern of SKS and S splitting measurements suggest the presence of a local scale mantle flow strongly controlled by the geometry and motion of the anisotropic slab.
    Description: Published
    Description: Montpellier, France
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: Seismic anisotropy ; SKS shear wave splitting ; subduction zones ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 3
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    Anisotropy and seismic attenuation tomography beneath a retreating subduction system: the Southern Tyrrhenian Sea case study (2012)
    Details
    Publication Date: 2017-04-03
    Description: The Southern Tyrrhenian subduction system shows a complex interaction among asthenospheric flow, subducting slab and overriding plate. To shed light on the deformations and mechanical properties of the slab and surrounding mantle, we investigated the attenuation and the anisotropic structure through the subduction region. The 3D attenuation results show high-attenuation shallow regions corresponding to the crustal layers, while the slab is imaged as a low-attenuation body bounded by high-attenuation regions located beneath the Aeolian magmatic arc. Between 100-200 km depth, in correspondence of high concentration of earthquakes, the slab is characterized by a spot of high attenuation. Such a feature could be related to the dehydration processes associated to the slab metamorphism. A high-attenuation anomaly is present in the mantle wedge beneath the Aeolian volcanic arc and could indicate mantle melting and slab dehydration and also to the large-scale serpentinization. We also investigated the anisotropic structure of the subduction zone by analyzing shear-wave splitting of the slab earthquakes. Seismic anisotropy reveals a complex pattern of anisotropy across the subduction zone. S-rays sample mainly the slab, showing variable fast directions and delay times. Comparison of S splitting measurements to P-wave velocity anomaly at 100-200 km depth shows that where the rays primarily sample the slab the delay times are small. In contrast, where S rays sample the mantle wedge, the delay times are quite high. This across-subduction variation of delay time depicts the slab as a weakly anisotropic region relative to the mantle above and below and suggests that the main source of anisotropy in the subduction zone is the deformation of the mantle above and below the slab induced by the retrograde motion of the slab.
    Description: Unpublished
    Description: Torino
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: subduction zone process ; mantle flow ; slab and mantle wedge anisotropy ; attenuation tomography ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 4
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    Shear wave splitting in southern tyrrhenian subduction zone (Italy) from CESIS and CAT/SCAN projects (2012)
    Details
    Publication Date: 2017-04-03
    Description: 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.
    Description: Published
    Description: Vienna
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: subduction zone process ; shear wave splitting ; deep seismicity ; Tyrrhenian Sea ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 5
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    Integrated SEED data archive for temporary seismic experiments (2010)
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    Publication Date: 2017-04-04
    Description: 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).
    Description: Unpublished
    Description: Sede Ispra | Via Curtatone 7, Roma
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: open
    Keywords: Instruments and techniques ; Waveform archive ; Messina Strait ; L'Aquila Fault System ; 04. Solid Earth::04.02. Exploration geophysics::04.02.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Seismic attenuation tomography beneath the retreating Southern Tyrrhenian Sea subduction system (2012)
    Details
    Publication Date: 2017-04-03
    Description: We investigate the seismic attenuation structure of the Ionian slab and surrounding mantle beneath the Southern Tyrrhenian subduction system. We present a high-resolution Vp, Vp/Vs, Qp and Qs models obtained by the inversion of high quality P- and S-waves t* from slab earthquakes. In our analysis we first located 304 earthquakes with M〉= 2.8 , depth 〉= 30 km and azimuthal gap 〈= 200 and we used a 3D a priori Vp and Vp/Vs model. Then, t* values were measured from spectra of P and S waves. For computing t* we have determined the corner frequency (fc) which has been estimated using a grid search over the frequency range 1 - 10 Hz using all the recordings for each event. The obtained t* values are then used in the inversion for the 3-D attenuation structure using, and kept fixed, the 3-D velocity model. Tomographic inversion show high-attenuation regions corresponding to the crustal layers with low values of Qs (values down to 200) but high values of Qp. The subducting slab is identified as a body of low attenuation, but heterogeneous in the Qs and Qp structure (Qs values up to 1100; Qp values up to 1200), surrounded by high-attenuation regions beneath the Aeolian magmatic arc. At 100 km depth the high Qp and Qs body is well reconstructed beneath the Calabrian arc and at 200 km depth it is extended offshore the Southern Tyrrhenian Basin beneath the Aeolian Islands. Between 100 and 200 km depth, the Ionian slab is characterized by intermediate depth seismicity, but Qp and Qs models clearly show the existence of high-attenuation region, with low values of Qs and high Qp/Qs structure. The observed low Qp and Qs anomalies could likely due to the fluids released from dehydrating minerals associated to the slab metamorphism. The observed low Qs anomalies regions between the slab and the Aeolian volcanic arc could be indicative of melting processes in the mantle and also of the large-scale serpentinization.
    Description: Published
    Description: Vienna
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: seismic attenuation tomography ; slab and mantle wedge fluids release ; subduction zone processes ; Southern Italy ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    SKS splittings in the southern Apennines-Calabrian arc region (southern Italy) (2012)
    Details
    Publication Date: 2017-04-04
    Description: 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.
    Description: Published
    Description: Chateau of Trest, Czech Republic
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: Seismic anisotropy ; SKS shear wave splitting ; southern Italy subduction system ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Lateral Changes of seismic anisotropy in the upper mantle around the Northern Apennines (2012)
    Details
    Publication Date: 2017-10-19
    Description: 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.
    Description: Published
    Description: Vienna
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: anisotropy ; SKS shear wave splitting ; Northern Apennines ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    “Messina 1908-2008”: Progetto di ricerca integrato per l’area Calabro - Peloritana. L’esperimento di sismica passiva (2010)
    Details
    Publication Date: 2017-04-04
    Description: 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.
    Description: Istituto Nazionale di Geofisica e Vulcanologia
    Description: Published
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: open
    Keywords: Seismic monitoring ; Waveform archive ; Messina Strait ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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