Compressional velocity structure and anisotropy in the uppermost mantle beneath Italy and surrounding regions

Mele, Giuliana; Rovelli, A.; Şeber, Dog̃an; Hearn, Thomas M.; Barazangi, Muawia

doi:10.1029/98jb00596

Cited by 56 publications

(52 citation statements)

References 70 publications

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“…This escarpment has long been recognized to be a major tectonic Piromallo & Morelli (2003), whereas the field of low Pn velocity of the uppermost mantle underneath Calabria is from Mele et al (1998). The area of He isotopes anomaly in western Sicily is from Caracausi et al (2005) and magmatism is from Argnani & Savelli (2001) and Savelli (2002).…”

Section: Strait Of Sicily and Malta Escarpmentmentioning

confidence: 99%

Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab

Argnani

2009

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The evolution of the southern Tyrrhenian subduction has been possibly controlled by distinct episodes of slab break-off as indicated by a critical review of the geological literature and by the analysis of purposely acquired multichannel seismic profiles. Within the proposed interpretation the first episode occurred from 8.5 to 4.0 Ma and affected the segment of the slab located in the Sardinia Channel, causing the abandonment of the Adventure thrust front in western Sicily. The second episode occurred between 2.5 and 1.6 Ma, affecting the segment of slab located north of Sicily, and was preceeded by rifting in the Strait of Sicily. The space and time location of these episodes appear controlled by discontinuities pre-existing within the subducted African plate that trend at high angle to the advancing subduction front. These discontinuities delimit segment of subducted slab that can be affected by slab break-off and can act as wayouts for magma and mantle derived He. The major of these discontinuities, the Malta Escarpment, has been reactivated in the Quaternary as a trench-perpendicular tear (STEP faults). Ultimately, the hierarchy in strength of these trench-perpendicular features could have affected the timing and amount of trench retreat and backarc opening.

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Section: Strait Of Sicily and Malta Escarpmentmentioning

confidence: 99%

Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab

Argnani

2009

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“…[4] It is well known that clear lateral Pn velocity variations and anisotropy exist in the uppermost mantle [e.g., Hearn, 1996Hearn, , 1999Hearn et al, 2004;Mele et al, 1998;Wang et al, 2002;Liang et al, 2004;Pei et al, 2002Pei et al, , 2004aPei et al, , 2004bPhillips et al, 2005]. Hearn et al [2004] obtained the shallow and deep Pn velocity variations within the mantle lid in China, via independent inversions for short and long paths, but he did not consider Pn anisotropy in his study.…”

Section: Introductionmentioning

confidence: 99%

Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography

et al. 2007

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We have obtained velocity images of the uppermost mantle beneath China by performing tomographic inversion of both Pn and Sn traveltimes. From the Annual Bulletin of Chinese Earthquakes, 99,139 Pn arrivals and 43,646 Sn arrivals were selected. Pn anisotropy was also obtained simultaneously with Pn velocity. Average Pn and Sn velocities are 8.05 and 4.55 km/s, respectively, and maximum velocity perturbations are about 3–4%. The Pn and Sn velocities are low in eastern China and high in western China. Particularly high velocities are associated with old basins (for example, Tarim, Junggar, Turpan‐Hami, Qaidam, and Sichuan) and stable craton (for example, Ordos). Low Sn velocities are found mainly throughout North China. In addition, velocities are relatively low beneath the central Tibetan Plateau and the North‐South Seismic Zone (along 103°E). In Tarim and central China where we observe strong anisotropy, the fast Pn velocity directions are consistent with the directions of maximum principal compressive stress as well as directions of crustal movement determined from Global Positioning System. Beneath the India‐Eurasia collision zone, the Pn anisotropy direction is parallel to the collision arc and nearly perpendicular to both the direction of maximum compression and crustal movement resulting from pure shear deformation. Both the velocity variations and anisotropy indicate that the Tibetan Plateau was extruded, and the mantle material beneath the plateau has flowed around the East Himalaya Syntax, while the remaining material has diverted northwestward beneath the Tarim Basin.

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“…Seismic anisotropy beneath France has already been studied using body waves of various wavelengths and incidence, providing different views of the anisotropy. Teleseismic shear wave splitting measurements [e.g., Barruol and Souriau, 1995;Granet et al, 1998] use short-wavelength SKS waves (X • 10 s) propagating through the lithosphere-asthenosphere system with small incidence angles and so provide azimuthal anisotropy with a horizontal resolution of the order of 10-and anisotropy perturbations [Barnford, 1977;Enderle et al, 1996;Him, 1977;Mele et al, 1998;Plenefisch et al, 1994], but, as in the case of the teleseismic shear wave, these data do not give any information on the three-dimensional orientation of the anisotropy. Nevertheless, P,, data offer a good azimuthal coverage in order to study the lateral variations of velocity and azimuthal anisotropy beneath France.…”

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confidence: 99%

Two‐dimensional anisotropic tomography of lithosphere beneath France using regional arrival times

Judenherc¹,

Granet²,

Boumbar³

1999

J. Geophys. Res.

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Abstract. This paper presents an anisotropic tomography study beneath France. Travel times of P• waves were inverted in order to simultaneously retrieve lateral variations of both seismic velocity and seismic anisotropy within the subcrustal lithosphere. The parameterization scheme uses a "classical" approach. The subcrustal lithosphere is modeled using a two-dimensional horizontal grid of nonoverlapping cells (0.5 ø x 0.5ø), each cell being characterized by an average slowness (the isotropic term of slowness) and an azimuthal anisotropy term. The

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Compressional velocity structure and anisotropy in the uppermost mantle beneath Italy and surrounding regions

Cited by 56 publications

References 70 publications

Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab

Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab

Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography

Two‐dimensional anisotropic tomography of lithosphere beneath France using regional arrival times

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