Morphotectonics (high resolution / LIDAR) and paleoseismology of the Trevaresse Fault (FACT axis Region 2 working group) - HAL Accéder directement au contenu
Poster de conférence Année : 2021

Morphotectonics (high resolution / LIDAR) and paleoseismology of the Trevaresse Fault (FACT axis Region 2 working group)

Résumé

This research project is part of the "Active faults - France" (FACT) action carried out by the RESIF consortium, one of whose objectives is to better understand seismotectonics and processes that control active deformation and seismic hazard in metropolitan France. In addition, the FACT action also aims to improve the temporal resolution of past earthquakes by developing paleoseismological investigations (trenches in Quaternary deposits), involving also sub-surface geophysical methods to locate potentially active structures under Quaternary sedimentary deposits. Within the framework of the RESIF consortium, we wish to re-launch work in Provence, which is one of the target areas of the FACT action and for which CEREGE is the regional coordinator (region 2). One of the proposed axes of our research project is to continue morphotectonic analyses in Provence by using new tools of very high resolution topography such as LiDAR imagery or SfM photogrammetry by drone. We first focus on the Trévaresse fault, whose historical reactivation was responsible for the Lambesc earthquake in 1909, one of the most destructive shaking in recent history in France, with strong damage to the villages. One of the advantages of this study area is that the morphology, surface rupture and fault segmentation associated with the activity of the geological structures have been partly evidenced by studies in the 2000s (Chardon & Bellier., 2003). Moreover, the surface rupture of the 1909 earthquake was identified in an open trench (Chardon et al., 2005) and the quaternary sediments excavated there were affected by multiple earthquakes. However, none of the formations in this trench have been dated and we therefore have no knowledge of the return times on this fault system. Our objective is to refine first the mapping of quaternary morphological surfaces and tectonic scarps. In 2021, our work focused on the morphological expression of active fault segments and geomorphological anomalies identified by exploiting high-resolution (1 meter) topography surveyed with airborne LiDAR by a team from the University of Caen (Thomas, 2018). These data have been complemented by field observations and new structural geology data and some geophysical surveys. In addition, photogrammetric surveys by drones were performed to complete very high-resolution topographic data (<10cm/pixel). In the near future (2022), we would like to open 1 to 2 paleoseismic trenches to confirm or not the presence of surface ruptures on other fault segments of the Trevaresse linked to the past occurrence of major earthquakes. If the potential sites seem too limited, we will reopen a trench in the area already excavated by Chardon et al. (2005) to date the affected deposits and eventually document more evidence of past earthquakes. Finally, this work aims at dating Quaternary morphological markers and paleoseismic events identified in the trenches. This step will be carried out by means of appropriate dating methods in the sedimentological context of the alluvial terraces of the Durance, by using the cosmogenic isotope technique (36Cl), and optical luminescence (OSL), these two methods being widely used at CEREGE.
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Dates et versions

halshs-04319947, version 1 (03-12-2023)

Identifiants

  • HAL Id : halshs-04319947 , version 1

Citer

Magali Rizza, Laurent Bollinger, Pablo Manzanares, Yann Klinger, Olivier Bellier, et al.. Morphotectonics (high resolution / LIDAR) and paleoseismology of the Trevaresse Fault (FACT axis Region 2 working group). international Workshop on "Active tectonics and dating", Sep 2021, Praz-sur-Arly, France. ⟨halshs-04319947⟩
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