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Earthquake disaster damage detection and mapping is one of the oldest challenges for remote sensing scientists. The usefulness of almost every type of active and passive sensor deployed on air or spaceborne platforms has been examined in the past. The advent and the development of unmanned aerial vehicles (UAVs) during the last decade have opened up many new opportunities for earthquake damage mapping. The main advantages of UAVs are the high spatial resolution, the possibility to acquire stereo images and produce both orthophotos and Digital Surface Models, and the flexibility of the platform. Earthquake-induced strain and rupture traces are expressed on the surface and imprinted in the topography on the landscapes of fault zones. UAVs provide an efficient and flexible solution for the acquisition of multi-angle imagery in order to reconstruct in fine scale the fault zone topography. The combination with RTK GNSS measurements provide the necessary accuracy to the final maps. A characteristic post-earthquake response based on UAV, GNSS and TLS technologies is presented in the current study. On March 3, 2021 (10:16:10 UTC) an earthquake with magnitude of 6.3 struck Thessaly, central Greece. The earthquake occurred in a region primarily characterized by active NW-SE trending normal faults, which belong to the Northern Thessaly fault zone. On March 4, 2021, (18:38:19 UTC), another earthquake struck the same area with magnitude 5.9. The University of Patras team detected innumerable lateral spreading, and liquefaction sand boils in close proximity with the active fault trace in the earthquake epicentral area. All these secondary earthquake environmental effects were mapped with UAV and traced with RTK GNSS. Co-seismic surface offset on the fault trace measured over than 25 cm. Our team mapped several places showing clear tectonic deformatin, although the intense agricultural modifications due to human activities disturbed the near surface stratigraphy. Therefore, only one favorable site for trenching was found. Two trenches 10 m long and 2.0 m wide with a maximum depth of almost 2.5 m were excavated and then mapped both by terrestrial photogrammetry and by a Terrestrial Laser Scanner.
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