Basin inversion: reactivated rift structures in the central Ligurian Sea revealed using ocean bottom seismometers
<p>The northern margin of the Ligurian Basin shows notable seismicity at the Alpine front, including frequent magnitude 4 events. Seismicity decreases offshore towards the Basin centre and Corsica, revealing a diffuse distribution of low-magnitude earthquakes. We analyse data of the amphibious...
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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/56fcee84dbd04080b9d555a95e494196 |
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| Sumario: | <p>The northern margin of the Ligurian Basin shows notable seismicity at the Alpine front, including frequent magnitude 4 events. Seismicity decreases
offshore towards the Basin centre and Corsica, revealing a diffuse distribution of low-magnitude earthquakes. We analyse data of the amphibious
AlpArray seismic network with focus on the offshore component, the AlpArray ocean bottom seismometer (OBS) network, consisting of 24 broadband OBSs
deployed for 8 months, to reveal the seismicity and depth distribution of micro-earthquakes beneath the Ligurian Sea.</p>
<p>Two clusters occurred between <span class="inline-formula">∼</span> 10 km to <span class="inline-formula">∼</span> 16 km depth below the sea surface, within the lower crust and uppermost mantle. Thrust faulting
focal mechanisms indicate compression and an inversion of the Ligurian Basin, which is an abandoned Oligocene–Miocene rift basin. The basin
inversion is suggested to be related to the Africa–Europe plate convergence. The locations and focal mechanisms of seismicity suggest reactivation
of pre-existing rift-related structures. Slightly different striking directions of presumed rift-related faults in the basin centre compared to
faults further east and hence away from the rift basin may reflect the counter-clockwise rotation of the Corsica–Sardinia block. High mantle S-wave
velocities and a low <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mtext>Vp</mtext><mo>/</mo><mtext>Vs</mtext></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="34pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e2987b21cb5fcde70dac84e76b4bf118"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-12-2553-2021-ie00001.svg" width="34pt" height="14pt" src="se-12-2553-2021-ie00001.png"/></svg:svg></span></span> ratio support the hypothesis of strengthening of crust and uppermost mantle during the Oligocene–Miocene
rifting-related extension and thinning of continental crust.</p> |
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