301 research outputs found
Spatial and temporal patterns of land subsidence and sinkhole occurrence in the Konya endorheic basin, Turkey
No full textThe endorheic Konya Basin is a vast aggradational plain in Central Anatolia, Türkiye. It occupies a significant portion of Konya Province, covering approximately 50,000 km2. The basin is subjected to intense groundwater withdrawal and extensive agricultural activities with excessive irrigation. These activities have led to human-induced hazards, such as sinkholes and regional land subsidence. Although sinkhole occurrence mainly occurs in the Karapınar area, land subsidence is primarily observed in the central sector of Konya city, with 2 million inhabitants, as well as in various parts of the basin. This study focuses on determining the extent and rate of land subsidence throughout the basin, understanding sinkhole formation, and unraveling their relationship with anthropogenic activities. For this purpose, Interferometric Synthetic Aperture Radar (InSAR) analysis of Sentinel-1 data from 2014 to 2022 was conducted to identify and assess land subsidence. We also used the land cover data and groundwater-level information to better understand the spatial and temporal patterns of land subsidence and sinkhole occurrence. Additionally, the land cover data were used to resolve spatial–temporal variations in the cultivated area and urbanization, which are the main factors governing groundwater exploitation in the region. Our study identified widespread subsidence zones with rates as high as 90 mm/y. Groundwater overexploitation to sustain extensive agricultural operations is the main cause of the high rate of land subsidence. Additionally, it was discovered that the number of sinkholes has substantially increased due to anthropogenic influences, currently amounting to as many as 660
PFC2D modelling of sinkhole cluster in karstic depressions
No full textDjamil Al-Halbouni, Sacha Emam, Eoghan P. Holoan, Abbas Taheri, Martin P.J. Schöpfer & Torsten Dah
Data files for: Geophysical investigations in the European Alps. doi:10.1594/PANGAEA.770504
No full textJoint interpretation of magnetotelluric and geomagnetic depth sounding data in the western European Alps offer new insights into the conductivity structure of the Earth's crust and mantle. This first large scale electromagnetic study in the Alps covers a cross-section from Germany to northern Italy and shows the importance of the alpine mountain chain as an interrupter of continuous conductors.
Poor data quality due to the highly crystalline underground is overcome by Remote Reference and Robust Processing techniques. 3d-forward-modelling reveals on the one hand interrupted dipping crustal conductors with maximum conductance of 4960 S and on the other hand a lithosphere thickening up to 208 km beneath the central western Alps. Graphite networks arising from Paleozoic sedimentary deposits are considered to be accountable for the occurrence of high conductivity and the distribution pattern of crustal conductors. The influence of huge sedimentary molasse basins on the electromagnetic data is suggested to be minor compared with the influence of crustal conductors. In conclusion, electromagnetic results can be attributed to the geological, tectonic and palaeogeographical background. Dipping direction (S-SE) and maximum angle (10.1°) of the northern crustal conductor reveal the main thrusting conditions beneath the Helvetic Alps whereas the existence of a crustal conductor in the Briançonnais supports theses about its palaeographic belonging to the Iberian Peninsula
Editorial: Management and monitoring of natural disasters using remote sensing and ground-based data
No full textIntroduction: Intensity and frequency of the natural disasters are increasing worldwide, above all also because of human activity and related effects on climate changes. In this context, ground deformation generated by catastrophic events represents a growing problem that affects hundreds of millions of people worldwide. The surface changes due to natural events, i.e., landslides, sinkholes, coastal erosion, volcanic activities, earthquakes, land subsidence, etc., can lead to structural damage of buildings and infrastructures, loss of extensive agricultural and/or natural areas, damage to tourist sites and cultural heritage, rise of salt wedges, regression of coastlines, and can have a significant economic and social impact. This negative impact can be further aggravated by climate change (e.g., sea level rise, modifications of rainfall intensity and period) and by climate change driven increased anthropogenic influence (e.g., groundwater withdrawal) in particular in low-lying coastal areas and unstable slopes. Ground deformation monitoring before (when possible), during and after a natural disaster plays a key role in the management of such natural hazards by providing cost-effective solutions for implementing risk mitigation strategies. Management and monitoring of natural events can be performed using different data: they can be acquired at various scales based on remote sensing techniques (in particular, but not limited to, InSAR–Interferometric Synthetic Aperture Radar) complemented with ground-based surveys (e.g., GNSS–Global Navigation Satellite System, precise leveling, Structure from Motion photogrammetry, Terrestrial Laser Scanning), including measurements from airplanes, helicopters, UAV (Unmanned Aerial Vehicle) as well as USVs (Unmanned Surface Vehicles) or also UUVs (Unmanned Underwater Vehicles). As each technique is characterized by advantages and disadvantages, when remote sensing data are used in conjunction with data provided by other techniques the quality of the final results improves (in terms of accuracy, costs and times of survey and data processing). In this way, the integration of data obtained from different sources play a fundamental role to improve the information that must be available for every risk mitigation activity
Photogrammetrie und geomechanische Diskrete-Elemente-Modellierung von Erdfällen und großskaligen Karstsenken
No full textSinkholes and depressions are typical landforms of karst regions. They pose a considerable natural hazard to infrastructure, agriculture, economy and human life in affected areas worldwide. The physio-chemical processes of sinkholes and depression formation are manifold, ranging from dissolution and material erosion in the subsurface to mechanical subsidence/failure of the overburden. This thesis addresses the mechanisms leading to the development of sinkholes and depressions by using complementary methods: remote sensing, distinct element modelling and near-surface geophysics.
In the first part, detailed information about the (hydro)-geological background, ground structures, morphologies and spatio-temporal development of sinkholes and depressions at a very active karst area at the Dead Sea are derived from satellite image analysis, photogrammetry and geologic field surveys. There, clusters of an increasing number of sinkholes have been developing since the 1980s within large-scale depressions and are distributed over different kinds of surface materials: clayey mud, sandy-gravel alluvium and lacustrine evaporites (salt). The morphology of sinkholes differs depending in which material they form: Sinkholes in sandy-gravel alluvium and salt are generally deeper and narrower than sinkholes in the interbedded evaporite and mud deposits. From repeated aerial surveys, collapse precursory features like small-scale subsidence, individual holes and cracks are identified in all materials. The analysis sheds light on the ongoing hazardous subsidence process, which is driven by the base-level fall of the Dead Sea and by the dynamic formation of subsurface water channels.
In the second part of this thesis, a novel, 2D distinct element geomechanical modelling approach with the software PFC2D-V5 to simulating individual and multiple cavity growth and sinkhole and large-scale depression development is presented. The approach involves a stepwise material removal technique in void spaces of arbitrarily shaped geometries and is benchmarked by analytical and boundary element method solutions for circular cavities. Simulated compression and tension tests are used to calibrate model parameters with bulk rock properties for the materials of the field site. The simulations show that cavity and sinkhole evolution is controlled by material strength of both overburden and cavity host material, the depth and relative speed of the cavity growth and the developed stress pattern in the subsurface. Major findings are: (1) A progressively deepening differential subrosion with variable growth speed yields a more fragmented stress pattern with stress interaction between the cavities. It favours multiple sinkhole collapses and nesting within large-scale depressions. (2) Low-strength materials do not support large cavities in the material removal zone, and subsidence is mainly characterised by gradual sagging into the material removal zone with synclinal bending. (3) High-strength materials support large cavity formation, leading to sinkhole formation by sudden collapse of the overburden. (4) Large-scale depression formation happens either by coalescence of collapsing holes, block-wise brittle failure, or gradual sagging and lateral widening.
The distinct element based approach is compared to results from remote sensing and geophysics at the field site. The numerical simulation outcomes are generally in good agreement with derived morphometrics, documented surface and subsurface structures as well as seismic velocities. Complementary findings on the subrosion process are provided from electric and seismic measurements in the area.
Based on the novel combination of methods in this thesis, a generic model of karst landform evolution with focus on sinkhole and depression formation is developed. A deepening subrosion system related to preferential flow paths evolves and creates void spaces and subsurface conduits. This subsequently leads to hazardous subsidence, and the formation of sinkholes within large-scale depressions. Finally, a monitoring system for shallow natural hazard phenomena consisting of geodetic and geophysical observations is proposed for similarly affected areas.Dolinen und Senken sind typische Landformen von Karstgebieten. Sie stellen in den betroffenen Gebieten weltweit ein erhebliches Naturrisiko für Infrastruktur, Landwirtschaft, Wirtschaft und das menschliche Leben dar. Die physikalisch-chemischen Prozesse der Entstehung solcher Senkungen sind vielfältig und reichen von Auflösung und Materialerosion im Untergrund bis zu mechanischem Absenken/Bruchs des Oberbodens. Diese Arbeit betrachtet die Mechanismen, die zur Entwicklung von Dolinen und Senken führen, anhand von verschiedenen geowissenschaftlichen Methoden:Fernerkundung, Gesteinsmechanischer Modellierung und pberflächennaher Geophysik.
Im ersten Teil werden detaillierte Informationen über den geologischen Hintergrund, Bodenstrukturen, Formen und die räumlich-zeitliche Entwicklung von Senkungen an einem sehr aktiven Karstgebiet am Toten Meer zusammengetragen. Dort bilden sich seit den 1980er Jahren immer größere Ansammlungen von Erdfällen, wie diese Phänomene auch oft genannt werden. Die Form der Erdfälle unterscheidet sich je nach Material, in dem sie entstehen: Erdfälle in Sand-Kies Böden und Salz sind im Allgemeinen tiefer und schmaler als Dolinen in den Schlammablagerungen des Toten Meeres. Wiederholte Aufnahmen aus der Luft mit Hilfe von Drohnen oder Ballons helfen dabei, kleine Absenkungen, einzelne Löcher und Risse zu identifizieren. Die Ursache dieser gefährlichen Absenkungen am Toten Meer ist in dem stetigen Fall des Seespiegels und der Bildung von starken Unterwasserkanälen zu sehen, die fortlaufend Material aus dem Boden herausspülen, sog. Subrosion.
Im zweiten Teil dieser Dissertation wird ein neuer, geomechanischer Modellierungsansatz zur Simulation des Wachstums von Hohlräumen im Untergrund und der Bildung von Senkungsstrukturen vorgestellt. Die Simulationen zeigen, dass die Entwicklung der Hohlräume und Erdfälle durch die Materialstärke, die Tiefe und Geschwindigkeit des Hohlraumwachstums und durch das sich bildende Spannungsmuster im Untergrund gesteuert wird. Die wichtigsten Ergebnisse der Studie sind: (1) Eine fortlaufend sich vertiefende Subrosion mit variabler Wachstumsgeschwindigkeit führt zu einem stärker fragmentierten Spannungsmuster im Boden. Es begünstigt das Bilden von ineinander verschachtelten Erdfällen (Cluster) in großen Vertiefungen. (2) Materialien mit niedriger Festigkeit (wie z.B. Schlamm) können keine großen Hohlräume bilden, und das Absinken geschieht durch ein allmähliches Absacken. (3) Materialien mit hoher Festigkeit (wie z.B. verfestigte Sande/Kiese oder Steinsalz) unterstützen die Bildung großer Hohlräume, was zu einem plötzlichen Zusammenbruch des Oberbodens führen kann. (4) Großskalige Senkungsstrukturen bilden sich entweder durch das Verschachteln von kleineren Dolinen, blockweise sprödem Versagen, oder das allmähliche Absinken mit seitlicher Erweiterung.
Die Ergebnisse der numerischen Simulationen stimmen im Allgemeinen sehr gut sowohl mit den beobachteten Senkungsformen an der Oberfläche überein, als auch mit Untergrundstrukturen beobachtet durch seismische und elektrische Methoden. Basierend auf der neuartigen Methodenkombination dieser Arbeit wird ein generisches Modell der Entwicklung von Senkungsstrukturen in Karstgebieten vorgestellt. Eine sich vertiefende Subrosion entlang von unterirdischen Kanälen erzeugt Hohlräume und führt in der Folge zu diesen gefährlichen Absenkungen und zur Bildung von Erdfällen innerhalb großer Vertiefungen
Geomagnetic depth sounding data from station Male, Western European Alps, 2008-10-01 to 2009-04-30
No full textA Vision on a UNESCO Global Geopark at the Southeastern Dead Sea in Jordan - Geosites and Conceptual Approach
No full textA vision for the establishment of a Geopark in Jordan is given in this work, with a subsequent application to the UNESCO Global Geopark programme. The Dead Sea area and its surroundings have suffered strong changes in the last decades, accompanied by a variety of natural hazards related to enhanced erosional processes. The aspiring Geopark will thematically encompass the influence that these changes and related natural hazards, including flash floods and subsidence, have had on the local population, from geological, over historical up to recent times. The hydrogeology and geomorphology, i.e., the connection between erosion by water, dissolution of minerals, and landscape evolution, will be the main guiding theme that connects the Eastern Rim Highlands with the Dead Sea rift valley through ephemeral wadis, vegetated springs areas, and traditionally communities. The creation of the Geopark is aimed at holistic, sustainable development and management of the area by eco-tourism, and includes education on water resource management, hazard awareness and resilience, as well as international research. We here present the conceptual approach to the initial development of a Geopark network in Jordan. In a narrative discourse, we highlight realised and further implementation steps, with an evaluation of the expected timeline, potential partner institutions, regional involvement and the chances for realisation
A Vision on a UNESCO Global Geopark at the Southeastern Dead Sea in Jordan — How Natural Hazards May Offer Geotourism Opportunities
No full textThis paper aims to identify and discuss the chances, solutions, and possible drawbacks related to the establishment of safe geotourism sites in subsidence-affected areas, exemplarily applied to the Ghor Al-Haditha sinkhole site at the southeastern shore of the Dead Sea. Such safe areas shall be established in the territory of the proposed future UNESCO Global Geopark (UGGp) in Jordan. The highlights of the geopark and the basis of its creation are the subsidence features and stream channels found along the SE shoreline of the Dead Sea, which form both a natural hazard and geological heritage of high international significance and have attracted many researchers so far. This recent and ongoing formation is related to the sharp regression of the lake, the specific geomechanical conditions, and the hydrogeologic and climatic background of the surroundings. Nearby communities have suffered in economic terms from these natural phenomena, including flash floods and droughts in this semi-arid to arid region. We here present a concept on how to integrate geoscientific research for hazard monitoring and early warning to maintain safety for inhabitants and visitors on the one hand and reach sustainable economic development through the establishment of geotourism sites on the other hand. This highlight area of the proposed UGGp serves as a starting example for delineating safe zones for walkways and infrastructure. This involves two-way knowledge transfer between spatial planning and hydrogeophysical monitoring, a network of community-supported geophysical surveillance, and regular maintenance and adaptation. The cross-cutting benefits for the territory involve the delineation of safe areas for agriculture and geotourism, the increase of sustainable tourism in the region with a shift towards alternative ways of income, more investment in infrastructure, a growth of international visibility of the region, enhanced environmental education with focus on responsible water usage, and involvement in international research and education projects
Geomechanical modelling of sinkhole development using Distinct Elements: Model verification for a single void space and application to the Dead Sea area
No full textMechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth∕diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth∕diameter values in each material type may partly reflect sinkhole growth trends.DESERVESIMULTA
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