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On 6 February 2023, an M7.8 devastating earthquake started rupturing the East Anatolian fault system in Turkey, resulting in intense shaking that lasted over a minute. A second earthquake of magnitude 7.5 struck near the city of Elbistan a few hours later. Both of these events are associated with the East Anatolian fault system. The earthquake sequence caused widespread damage and collapse of structures in densely populated areas throughout the Southern Turkey and Northern Syria regions and a very large number of human losses. This study focuses on the correlation of the ground deformation with the critical exposure of the infrastructures of Gaziantep and Kahramanmaraş cities. The estimation of the ground deformation of the affected area is achieved with the use of Copernicus Sentinel-2 products and the Normalized Cross Correlation algorithm (NCC) of image matching. The results of the East–West component show that specific sections of the region moved towards the East direction, reaching displacement measurements of 5.4 m, while other sections moved towards the West direction, reaching displacement measurements of 2.8 m. The results of the North–South component show that almost the whole affected area moved towards the North direction, with specific areas reaching displacements of 5.5 m, and a few exemptions, as some areas moved towards the South direction, with displacements reaching even 6.9 m. Regarding the cities of Kahramanmaraş and Gaziantep, their estimated movement direction is North-West and North-East, respectively, and is consistent with the movements of the Arabian and Anatolian Plates in which they are located. Important infrastructures of the study areas (education, museums, libraries, hospitals, monuments, airports, roads and railways) are superimposed on the findings, enabling us to detect the critical exposure rapidly. [ABSTRACT FROM AUTHOR]

Coastal environments are highly recognized for their spectacular morphological features and economic activities, such as agriculture, maritime traffic, fishing, and tourism. In the context of climate change and the evolution of physical processes, the occurrence of intense natural phenomena adjacent to populated coastal areas may result in natural hazards, causing human and/or structural losses. As an outcome, scientific interest in researching and assessing multi-hazard susceptibility techniques has increased rapidly in an effort to better understand spatial patterns that are threatening coastal exposed elements, with or without temporal coincidence. The islands of Milos and Thira (Santorini Island) in Greece are prone to natural hazards due to their unique volcano-tectonic setting, the high number of tourist visits annually, and the unplanned expansion of urban fabric within the boundaries of the low-lying coastal zone. The main goal of this research is to analyze the onshore coastal terrain's susceptibility to natural hazards, identifying regions that are vulnerable to soil erosion, torrential flooding, landslides and tsunamis. Therefore, the objective of this work is the development of a multi-hazard approach to the South Aegean Volcanic Arc (SAVA) islands, integrating them into a superimposed susceptibility map utilizing Multi-Criteria Decision-Making (MCDM) analysis. The illustrated geospatial workflow introduces a promising multi-hazard tool that can be implemented in low-lying coastal regions globally, regardless of their morphometric and manmade characteristics. Consequently, findings indicated that more than 30% of built-up areas, 20% of the transportation network, and 50% of seaports are within the high and very high susceptible zones, in terms of the Extended Low Elevation Coastal Zone (ELECZ). Coastal managers and decision-makers must develop a strategic plan in order to minimize potential economic and natural losses, private property damage, and tourism infrastructure degradation from potential inundation and erosion occurrences, which are likely to increase in the foreseeable future. [ABSTRACT FROM AUTHOR]

Infrastructure monitoring can facilitate the evaluation of capacity and functionality loss and therefore provide valuable data and evidence for reliable, lifetime and automated risk assessments. Terrestrial monitoring systems can provide information about assets and their condition. Yet, they fall short of engineering requirements related to the history of the asset loading, deterioration and potential damage, which is of paramount importance in risk-based decision-making by infrastructure operators. This capability gap can be filled by Persistent Scatterer Interferometry (PSI) Monitoring in conjunction with engineering forensics and judgment. This paper puts forward this hybrid approach to assess the structural condition of a landmark bridge by coupling advanced Differential SAR Tomography (D-TomoSAR) techniques with an adaptive deformation model, environmental measurements and engineering evidence and evaluations. A dataset of 360 Sentinel A &B images covering the period between 10/2014 and 2/2020 and temperature records to account for seasonal deformation were deployed. Displacement products, such as the development of annual displacement and time series were calculated demonstrating a strong correlation with temperature variation and resulting deformations of the asset. The spatiotemporally evolving deformation trends of the bridge superstructure were derived, and vulnerable deck locations were identified on the basis of engineering forensics, judgment and progressive displacements calculated from the D-TomoSAR technique. The vertical displacement profile at the critical deck location was developed reaching a displacement velocity of 1.8 mm/year and potential deterioration issues are manifested as potential causes of the observed geometric alterations. Based on the D-TomoSAR results matched with engineering evidence and on-site visual inspections and judgment, this study contributed to the decision-making process. This research is a pilot showcase of D-TomoSAR for the bridge monitoring, not only providing mm-level quantitative measurements of the bridge in a 6-year observation span using medium resolution Sentinel-1 SAR images alone but also indirectly identifying potential structural defects in the north section of the bridge. This research is a primer example of how we can deploy diverse evidence to facilitate targeted adaptation measures and prioritize restoration strategies to facilitate asset owners in better decision making. [ABSTRACT FROM AUTHOR]

On 2 December 2020, a moderate and shallow Mw = 4.6 earthquake occurred in Boeotia (Central Greece) near the city of Thiva. Despite its magnitude, the co-seismic ground deformation field was detectable and measurable by Sentinel-1, ascending and descending, synthetic aperture interferometry radar (InSAR) acquisitions. The closest available GNSS station to the epicenter, located 11 km west, measured no deformation, as expected. We proceeded to the inversion of the deformation source. Moreover, we reassessed seismological data to identify the activated zone, associated with the mainshock and the aftershock sequence. Additionally, we used the rupture plane information from InSAR to better determine the focal mechanism and the centroid location of the mainshock. We observed that the mainshock occurred at a shallower depth and the rupture then expanded downdip, as revealed by the aftershock distribution. Our geodetic inversion modelling indicated the activation of a normal fault with a small left-lateral component, length of 2.0 km, width of 1.7 km, average slip of 0.2 m, a low dip angle of 33°, and a SW dip-direction. The inferred fault top was buried at a depth of ~0.5 km, rooted at a depth of ~1.4 km, with its geodetic centroid buried at 1.0 km. It was aligned with the Kallithea fault. In addition, the dip-up projection of the modeled fault to the surface was located very close (~0.4 km SW) to the mapped (by existing geological observations) trace of the Kallithea fault. The ruptured area was settled in a transition zone. We suggest the installation of at least one GNSS and seismological station near Kallithea; as the activated zone (inferred by the aftershock sequence and InSAR results) could yield events with M ≥ 5.0, according to empirical laws relating to rupture zone dimensions and earthquake magnitude. [ABSTRACT FROM AUTHOR]

A plethora of subsidence events has been repeatedly reported in high density urban environments. The purpose of this study is to introduce specific areas around the riverbeds of the urban hidden streams in the city of Athens presenting high risk in terms of ground subsidence. The study area comprises the centre of Athens and more specifically the Municipalities of Athens, Tavros, Kallithea, Daphne, Hymettus and Ilisia where the ancient rivers of Ilissos and Eridanus naturally flow through a heavily populated city. It wasn't until the early 1960s that the two rivers were completely channelled and partly covered along their course during the urbanization process which allowed the construction of the modern boulevards, roads, recreation and open space areas as long as parking areas. The route of today's concealed rivers and streams poses a serious risk of potential ground subsidence concerning the erosion of streams' bank permeable soil formations. Following this approach, areas of influence (buffer zones) were determined on each side of the subterranean urban rivers Ilissos and Eridanus. In particular, an inventory of literature and references such as, historical maps and drawings, technical studies as well as modern topographic and geological maps, land use/land cover maps were created and collected in a geospatial database. It is worth mentioning that a main part of this study was the utilization and analysis of satellite radar data of the time period 2012–2016, in order to detect vertical displacements (mm/year) and correlate these with the above-mentioned spatial data of Athens city. [ABSTRACT FROM AUTHOR]