Coastline evolution is a proxy of coastal erosion, defined as the wasting of land along the shoreline due to a combination of natural and/or human causes. For countries with a sea border, where a significant proportion of the population lives in coastal areas, shoreline retreat has become a very serious global problem. Remote sensing data and photogrammetry have been used in coastal erosion mapping for many decades. In the current study, multi-date analogue aerial photos, digital aerial photos, and declassified satellite imagery provided by the U.S. Geological Survey (USGS), Pleiades satellite data, and unmanned aerial vehicle images were combined for accurate mapping of the southwestern Lefkada (Ionian Sea, Greece) coastline over the last 73 years. Different photogrammetric techniques were used for the orthorectifation of the remote sensing data, and geographical information systems were used in order to calculate the rates of shoreline change. The results indicated that the southwest shoreline of Lefkada Island is under dynamic equilibrium. This equilibrium is strongly controlled by geological parameters, such as subsidence of the studied shoreline during co-seismic deformation and mass wasting. The maximum accretion rate was calculated at 0.55 m per year, while the respective erosion rate reached −1.53 m per year.
On 3 March 2021, a strong shallow earthquake affected northern Thessaly, Greece, with an epicenter close to Damasi village causing significant destruction of many stone houses. In this contribution, we provide fieldwork observations, satellite radar interferometry, mapping of the active faults exposed in the epicentral area, liquefactions and coseismic surface ruptures, and preliminary geomorphological analyses of the epicentral area. The geomorphological analysis is based on air photographs, digital surface models analysis, Real-Time Kinematik (RTK) measurements with Global Navigation Satellite System (GNSS) receivers, and data from UAV flight campaigns. Although the seismotectonic setting of the area is complex and there is an apparent mismatch between field and interferometric data, the results of our investigations suggest that at least three fault segments were reactivated by the major shocks of the March seismic sequence. These tectonic structureslikely represent the westward propagation of the Tyrnavos Graben, where newly formed and inherited low-angle faults interplay in a complex manner.
12 January 2018 in Bulletin of Engineering Geology and the Environment
Field investigation, Microfacies analysis, and biostratigraphy have been carried out in the central parts of the Ionian Basin (Aetoloakarnania area, Western Greece) in order to decipher the depositional environments that developed during the accumulation of the Upper Cretaceous to Eocene carbonate succession. Three different Standard Microfacies types (SMF) have been observed, corresponding to two different depositional environments (Facies Zones or FZ) of a platform progradation. The three SMF types which occur in the study area during the Upper Cretaceous to Eocene are: 1. SMF 3 that includes mudstone/wackestone with planktic foraminifera and radiolaria, corresponding to toe-of-slope (FZ: 3), 2. SMF 4, which can be classified as polymict clast-supported microbreccia, indicating a toe-of-slope-slope environment (FZ: 4) and 3. SMF 5 which is characterized by allochthonous bioclastic breccia and components deriving from adjacent platforms and which reflects a slope environment. Microfacies analysis provided evidence of a change in the origin of sedimentary components and biota showing the transition from toe-of-slope to slope, as well as a change in organism distribution.
Assessment of landslide hazard across mountains is imperative for public safety. Pre- and post-earthquake landslide mapping envisage that landslides show significant size changes during earthquake activity. One of the purposes of earthquake-induced landslide investigation is to determine the landslide state and geometry and draw conclusions on their mobility. This study was based on remote sensing data that covered 72 years, and focused on the west slopes of the Skolis Mountains, in the northwest Peloponnese. On 8 June 2008, during the strong Movri Mountain earthquake (Mw = 6.4), we mapped the extremely abundant landslide occurrence. Historical seismicity and remote sensing data indicate that the Skolis Mountain west slope is repeatedly affected by landslides. The impact of the earthquakes was based on the estimation of Arias intensity in the study area. We recognized that 89 landslides developed over the last 72 years. These landslides increased their width (W), called herein as inflation or their length (L), termed as enlargement. Length and width changes were used to describe their aspect ratio (L/W). Based on the aspect ratio, the 89 landslides were classified into three types: I, J, and Δ. Taluses, developed at the base of the slope and belonging to the J- and Δ-landslide types, are supplied by narrow or irregular channels. During the earthquakes, the landslide channels migrated upward and downward, outlining the mobility of the earthquake-induced landslides. Landslide mobility was defined by the reach angle. The reach angle is the arctangent of the landslide’s height to length ratio. Furthermore, we analyzed the present slope stability across the Skolis Mountain by using the landslide density (LD), landslide area percentage (LAP), and landslide frequency (LF). All these parameters were used to evaluate the spatial and temporal landslide distribution and evolution with the earthquake activity. These results can be considered as a powerful tool for earthquake-induced landslide disaster mitigation
27 July 2017 in Bulletin of the Geological Society of Greece
A paleoseismological analysis has been performed at the East Giouchtas Fault. This fault dips to the east and represents a pure normal fault. The East Giouchtas Fault forms an intrabasinal high in the Heraklion basin with its conjugate fault the West Giouchtas Fault. A natural surface has been prepared and logged in detail in order to detect the most significant parameters related to the ground shaking impact on the area. Investigating past earthquakes characteristics attributed to the East Giouchtas Fault and through sample dating we conclude that the studied fault is related to at least four strong events of 6.4 magnitude. The fault is also characterized by 20-40 cm tectonosedimentatry displacements and slip rates of 0.25 mm/yr. Thus, the proximity of the fault to the highly populated Heraklion city and Minoan Knossos monument urges the need for an adequate hazard assessment of the area.