Imaging the Sicily Channel Rift Zone (Central Mediterranean) with seismic ambient noise tomography.

The tectonics of the Sicily Channel, located in the Central Mediterranean, are thought to be driven by the Calabrian back-arc system moving south-eastwards and the north moving African plate. The Channel is characterized by a seismically and volcanically active rift zone, which extends for more than 600 km in length offshore from the south of Sardinia to the south-east of Malta. Much of the observations we have today are either limited to the surface and the upper crust, or are broader and deeper from regional seismic tomography, missing important details about the lithospheric structure and dynamics. The project GEOMED () addresses this issue by processing all the seismic data available in the region in order to understand better the geodynamics of the Central Mediterranean.We use seismic ambient noise recorded on more than 50 stations located on Algeria, Italy (Lampedusa, Linosa, Pantelleria, Sardinia (LISARD seismic network), Sicily), Libya, Malta, and Tunisia to generate high-resolution seismic tomography maps for the region at different depths. We measure Rayleigh-wave phase velocities with periods ranging from 5 to 100 seconds sampling through the entire lithosphere. We find that at short periods (<25 s), paths of station-pairs crossing across Africa and Italy have slower velocities than those crossing the Tyrrhenian and Ionian basins indicating that these paths are sampling thick continental crust. However, station pairs limited to the Sicily Channel Rift Zone (SCRZ) have faster phase velocities for periods > 20 s comparable to those beneath the basins suggesting that the SCRZ has a thinner crust. The seismic velocity maps are compared with the regional tectonics, seismicity, volcanic activity and other geophysical studies to present a more holistic understanding of the processes involved.This project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under the Marie Sk&#322;odowska-Curie grant agreement No. 843696.

Download Full-text

Geodynamics of the Central Mediterranean (GEOMED) inferred from ambient seismic noise

10.5194/egusphere-egu21-6028 ◽

2021 ◽

Author(s):

Matthew Agius ◽

Fabrizio Magrini ◽

Giovanni Diaferia ◽

Fabio Cammarano ◽

Claudio Faccenna ◽

...

Keyword(s):

Seismic Noise ◽

Rift Zone ◽

Ambient Seismic Noise ◽

Special Focus ◽

Tyrrhenian Sea ◽

The European Union ◽

Central Mediterranean ◽

Phase Velocity Dispersion ◽

Radial Anisotropy ◽

Sicily Channel

The Central Mediterranean, the area encompassing Italy, Sardinia, Tunisia and Libya, is characterised by multiple tectonic processes (plate convergence, subduction, and backarc extension). The evolution and interaction of the plate margins within this relatively small area are still being unravelled particularly at the adjacent region known as the Sicily Channel located between Sicily, Tunisia, Libya and Malta. This Channel is characterised by a seismically and volcanically active rift zone. Much of the observations we have today for the southern parts of the Calabrian arc are either limited to the surface and the upper crust, or are broader and deeper from regional seismic tomography, missing important details about the lithospheric structure and dynamics. The project GEOMED (https://geomed-msca.eu) addresses this issue by processing all the seismic data available in the region in order to understand better the geodynamics of the Central Mediterranean.We measure Rayleigh- and Love-wave phase velocities from ambient seismic noise recordings to infer the structures of the Central Mediterranean, from the Central Apennines to the African foreland, with a special focus on the Sicily Channel Rift Zone (SCRZ). The phase-velocity dispersion curves have periods ranging from 5 to 100 seconds and sample through the entire lithosphere. We invert the dispersion data for isotropic and polarised shear velocities with depth and infer crustal thickness and patterns of radial anisotropy. We find that continental blocks have thick crust (30-50 km), whereas beneath the SCRZ the crust is thin (<25 km), and thinner beneath the Tyrrhenian Sea. Beneath the SCRZ and the Tyrrhenian Sea, the crustal shear velocities are characterised by positive radial anisotropy (VSH>VSV) indicative of horizontal flow or extension, whereas the uppermost mantle is characterised by slow shear velocities indicative of warmer temperatures and strong negative radial anisotropy (VSH>VSV) indicative of vertical flow. We discuss the relevance of these findings together with other geophysical studies such as the regional seismicity and GPS velocity vectors to identify the rifting process type of the SCRZ.This project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under the Marie Sk&#322;odowska-Curie grant agreement No 843696.

Download Full-text

Seismic ambient noise around the South China Sea: seasonal and spatial variations, and implications for its climate and surface circulation

Marine Geophysical Research ◽

10.1007/s11001-013-9176-6 ◽

2013 ◽

Vol 34 (3-4) ◽

pp. 449-459 ◽

Cited By ~ 2

Author(s):

Da Huo ◽

Ting Yang

Keyword(s):

South China Sea ◽

South China ◽

Ambient Noise ◽

Spatial Variations ◽

The South China Sea ◽

The South ◽

Seismic Ambient Noise ◽

China Sea ◽

Surface Circulation ◽

Seasonal And Spatial Variations

Download Full-text

Lower plate extension of a retreating subduction zone: case study of the Sicily Channel Rift Zone

10.5194/egusphere-egu21-12579 ◽

2021 ◽

Author(s):

Eline Le Breton ◽

Mirko Carlini ◽

Robert Neumeister ◽

Jessica Ecke ◽

Nicolo Chizzini ◽

...

Keyword(s):

Subduction Zone ◽

Rift Zone ◽

Western Mediterranean ◽

Lower Plate ◽

Accretionary Wedge ◽

Tectonic Structures ◽

Central Mediterranean ◽

Adriatic Plate ◽

Sicily Channel ◽

Seismic Lines

The Alpine-Mediterranean belt is remarkable because of the strong arcuation of its subduction front and the abundance of extensional basins developed within an overall compressional setting. Both resulted from rapid slab rollback and trench retreat especially in Neogene time, accompanied by upper-plate extension and the opening of the Western Mediterranean basins. The Strait of Sicily is a very interesting geological area in the Western-Central Mediterranean, as it has undergone tectonic extension and opening of a rift zone (Sicily Channel Rift Zone, SCRZ) on the lower plate (Africa) of the subduction zone, marked by the Gela Front and the Calabrian Accretionary Wedge, located south and south-east of Sicily, respectively. Furthermore, the SCRZ is important for understanding and quantifying the independent motion and counter-clockwise rotation of the Adriatic plate in Neogene time (Le Breton et al. 2017). However, the exact timing, tectonic style and amount of deformation along the SCRZ remain unclear.To tackle these questions, we re-evaluate multichannel seismic reflection profiles across the SCRZ (CROP seismic lines M24 and M25), as well as a series of seismic lines correlated with boreholes data from the VIDEPI project (www.videpi.com). Main stratigraphic horizons and tectonic structures are mapped in a 3D database using the MOVE Software (provided by Petex). Preliminary results indicate ~30 km of NE-SW extension through the Pantelleria Rift and onset of syn-rift deposition during the upper Messinian, which could be related with the fast slab retreat of the Calabrian Arc.&#160;References:Le Breton E.,&#160;M.R. Handy, G. Molli and K. Ustaszewski (2017).&#160;Post-20 Ma motion of the Adriatic plate &#8211; new constrains from surrounding orogens and implications for crust-mantle decoupling, Tectonics, doi:10.1002/2016TC004443

Download Full-text

Predictive distribution models of European hake in the south-central Mediterranean Sea

Hydrobiologia ◽

10.1007/s10750-017-3338-5 ◽

2017 ◽

Vol 821 (1) ◽

pp. 153-172 ◽

Cited By ~ 3

Author(s):

G. Garofalo ◽

S. Fezzani ◽

F. Gargano ◽

G. Milisenda ◽

O. Ben Abdallah ◽

...

Keyword(s):

Mediterranean Sea ◽

Predictive Distribution ◽

The South ◽

Distribution Models ◽

Central Mediterranean ◽

South Central ◽

Central Mediterranean Sea ◽

European Hake

Download Full-text

Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia

Geophysical Journal International ◽

10.1093/gji/ggaa553 ◽

2020 ◽

Vol 224 (3) ◽

pp. 1684-1704

Author(s):

Alexandra Mauerberger ◽

Valérie Maupin ◽

Ólafur Gudmundsson ◽

Frederik Tilmann

Keyword(s):

Seismic Anisotropy ◽

Broad Band ◽

Shear Velocity ◽

Velocity Variation ◽

The South ◽

Study Region ◽

Lithospheric Thickness ◽

Phase Velocities ◽

The North ◽

Southern Norway

SUMMARY We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.

Download Full-text