Application of SfM technique for measuring near-field earthquake-induced failures; case studies from Greece

One of the main issues that a post-earthquake field survey must address is reporting the failures induced by the seismic event. However, it is well known that mapping these features is not always feasible due to several factors e.g. near-vertical slopes, coastall cliffs, high risk to human surveys. In order to overcome this issue and to quantitatively describe the earthquake-induced geological failures e.g. landslides and liquefaction-induced lateral spreading, remote sensing techniques were applied during the last decades such as Interferometric Synthetic Aperture Radar (InSAR), Light Detection and Ranging (LiDAR) and photogrammetric surveys. The latter one, a photogrammetric survey, is frequently conducted by use of Unmanned Aerial Vehicles (UAV), such as multicopters equipped with webcams, digital cameras and other sensors. The images acquired by the UAV can be processed using the Structure from Motion (SfM) image technique, thus providing a 3D point cloud. This study presents the application of the SfM approach in two post-earthquake UAV & field surveys conducted in Greece (Lefkada and Kos islands) for reporting the triggering of a deepseated landslide and a lateral spreading case study, respectively.