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Expérience MADAM : caractérisation sismotectonique d’une microplaque en formation (Grèce)

Abstract : Western Greece is a transition zone between an oceanic subduction and a continental collision. To the South, the relics of the oceanic lithosphere of the Tethys Ocean are subducting beneath the Anatolia with a N-S convergence rate reaching ∼ 35 mm/yr. To the North, the collision between the thick Apulian platform and the Eurasian plate accommodates a NE-SW shortening of about 5 mm/yr. The Ionian Islands-Akarnanian Block (IAB) is a microplate located on western Greece that accommodates the complex deformations between these two systems. Today the IAB remains poorly studied compared to the large surrounding tectonic structures such as the Corinth Gulf. Many questions remain about the IAB, mainly about its link with the surrounding structures, the location of the deformation but also about the limits of this microplate. The boundary between the IAB and continental Greece is still a subject of discussion. To better characterize this boundary, a local seismological campaign (MADAM) was conducted. Our temporary seismic network was designed to best record Akarnanian seismicity. In this thesis, I present the processing and the analysis of these seismological data. Using a semi-automated event detection and picking program, we detected more than 15,000 earthquakes over 39 months between 2015 and 2018. To well constrain the events locations, we determined a new robust 1D velocity model for the region. Using our database and our velocity model, we were able to locate 12723 seismic events and determine 571 focal mechanisms. Currently, this represents the largest catalog of seismicity for Akarnania. The seismic activity of the region is characterized by the presence of numerous clusters. The study of these clusters shows two different formation and evolution processes with, on the one hand, a mainshock-aftershocks process and, on the other hand, a fluid migration process possibly associated with slow slip events. A large seismic plane under th e western Corinth Gulf is also highlighted by the seismicity. Its study allows to present it as an immature north-dipping detachment plane that participates in the opening of the Corinth Gulf and joins at depth the brittle-ductile boundary of the crust. The background seismicity also allows us to refine the mapping of active faults in the region and to provide information on the deformation that is characterized by overall N-S extension and a large senestral transform system. Finally, we were able to better characterize the Akarnanian region and propose a geodynamic model consistent with the regional framework.
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Submitted on : Thursday, November 10, 2022 - 6:07:58 PM
Last modification on : Monday, November 14, 2022 - 1:14:16 PM

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  • HAL Id : tel-03848424, version 1

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Valentine Lefils. Expérience MADAM : caractérisation sismotectonique d’une microplaque en formation (Grèce). Sciences de la Terre. Université Paris sciences et lettres, 2022. Français. ⟨NNT : 2022UPSLE002⟩. ⟨tel-03848424⟩

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