3D crustal structure of the Ligurian Basin revealed by surface wave tomography using ocean bottom seismometer data
<p>The Liguro-Provençal basin was formed as a back-arc basin of the retreating Calabrian–Apennines subduction zone during the Oligocene and Miocene. The resulting rotation of the Corsica–Sardinia block is associated with rifting, shaping the Ligurian Basin. It is still debated whether oceanic...
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| Autores principales: | , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/a6ba293843944ee780867242e4df405d |
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| Sumario: | <p>The Liguro-Provençal basin was formed as a back-arc basin of
the retreating Calabrian–Apennines subduction zone during the Oligocene and
Miocene. The resulting rotation of the Corsica–Sardinia block is associated
with rifting, shaping the Ligurian Basin. It is still debated whether
oceanic or atypical oceanic crust was formed or if the crust is continental
and experienced extreme thinning during the opening of the basin. We perform
ambient noise tomography, also taking into account teleseismic events, using
an amphibious network of seismic stations, including 22 broadband ocean
bottom seismometers (OBSs), to investigate the lithospheric structure of the
Ligurian Basin. The instruments were installed in the Ligurian Basin for
8 months between June 2017 and February 2018 as part of the AlpArray
seismic network. Because of additional noise sources in the ocean, OBS data
are rarely used for ambient noise studies. However, we carefully pre-process
the data, including corrections for instrument tilt and seafloor compliance
and excluding higher modes of the ambient-noise Rayleigh waves. We calculate
daily cross-correlation functions for the AlpArray OBS array and surrounding
land stations. We also correlate short time windows that include teleseismic
earthquakes, allowing us to derive surface wave group velocities for longer
periods than using ambient noise only. We obtain group velocity maps by
inverting Green's functions derived from the cross-correlation of ambient
noise and teleseismic events, respectively. We then used the resulting 3D
group velocity information to calculate 1D depth inversions for S-wave
velocities. The group velocity and shear-wave velocity results compare well
to existing large-scale studies that partly include the study area. In onshore France, we observe a high-velocity area beneath the Argentera Massif,
roughly 10 km below sea level. We interpret this as the root of the
Argentera Massif. Our results add spatial resolution to known seismic
velocities in the Ligurian Basin, thereby augmenting existing seismic
profiles. In agreement with existing seismic studies, our shear-wave
velocity maps indicate a deepening of the Moho from 12 km at the
south-western basin centre to 20–25 km at the Ligurian coast in the north-east
and over 30 km at the Provençal coast. The maps also indicate that the
south-western and north-eastern Ligurian Basin are structurally separate. The
lack of high crustal <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>v</mi><mi mathvariant="normal">P</mi></msub><mo>/</mo><msub><mi>v</mi><mi mathvariant="normal">S</mi></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d8f12ae4c2173db096ca8a8bd5586b6e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-12-2597-2021-ie00001.svg" width="30pt" height="14pt" src="se-12-2597-2021-ie00001.png"/></svg:svg></span></span> ratios beneath the south-western part of
the Ligurian Basin preclude mantle serpentinisation there.</p> |
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