Preprints
https://doi.org/10.5194/se-2021-9
https://doi.org/10.5194/se-2021-9

  05 Feb 2021

05 Feb 2021

Review status: this preprint is currently under review for the journal SE.

Basin inversion: Reactivated rift structures in the Ligurian Sea revealed by OBS

Martin Thorwart1, Anke Dannowski2, Ingo Grevemeyer2, Dietrich Lange2, Heidrun Kopp1,2, Florian Petersen2, Wayne Crawford3, Anne Paul4, and the AlpArray Working Group Martin Thorwart et al.
  • 1CAU, Institute of Geosciences, Christian-Albrechts-Universität zu Kiel, 24105 Kiel, Germany
  • 2GEOMAR, Marine Geodynamics, Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany
  • 3IPGP, Laboratoire de Géosciences Marines, Institut de Physique du Globe de Paris, Paris, 75238 Cedex 5, France
  • 4Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, UGE, ISTerre, 38000 Grenoble, France
  • For the complete team list visit the link which appears at the end of the paper.

Abstract. 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 OBS network, consisting of 24 broadband ocean bottom seismometers deployed for eight months, to reveal the seismicity and depth distribution of micro-earthquakes beneath the Ligurian Sea.

Two clusters occurred between ~10 km to ~16 km depth below 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 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 structures. Slightly different striking directions of faults in the basin centre compared to faults further east and hence away from the abandoned rift may mimic the counter-clockwise rotation of the Corsica-Sardinia block during ~20–16 Ma. The observed cluster events support the hypothesis of strengthening of crust and uppermost mantle during rifting related extension and thinning of continental crust.

Martin Thorwart et al.

Status: open (until 25 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Martin Thorwart et al.

Martin Thorwart et al.

Viewed

Total article views: 236 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
181 53 2 236 1 0
  • HTML: 181
  • PDF: 53
  • XML: 2
  • Total: 236
  • BibTeX: 1
  • EndNote: 0
Views and downloads (calculated since 05 Feb 2021)
Cumulative views and downloads (calculated since 05 Feb 2021)

Viewed (geographical distribution)

Total article views: 194 (including HTML, PDF, and XML) Thereof 194 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 08 Mar 2021
Download
Short summary
We analyse broadband ocean bottom seismometer data of the AlpArray OBS network in the Ligurian Basin. Two earthquake clusters with thrust faulting focal mechanisms indicate compression of the rift basin. The locations of seismicity suggest reactivation of pre-existing rift structures and strengthening of crust and uppermost mantle during rifting related extension. Slightly different striking directions of faults may mimic the counter-clockwise rotation of the Corsica-Sardinia block, ~20–16 Ma.