Sinkholes and uvalas in evaporite karst: spatio-temporal development with links to base-level fall on the eastern shore of the Dead Sea

Enclosed topographic depressions are characteristic of karst landscapes on Earth. The developmental relationship between depression types, such as sinkholes (dolines) and uvalas, has been the subject of debate, mainly because the long developmental timescales in classical limestone karst settings impede direct observation. Here we characterize the morphometric properties and spatio-temporal development of ∼1150 sinkholes and five uvalas formed from ∼1980 to 2017 in an evaporite karst setting along the eastern coast of the hypersaline Dead Sea (at Ghor Al-Haditha, Jordan). The development of sinkhole populations and individual uvalas is intertwined in terms of onset, evolution and cessation. The sinkholes commonly develop in clusters, within which they may coalesce to form compound or nested sinkholes. In general, however, the uvalas are not defined by coalescence of sinkholes. Although each uvala usually encloses several clusters of sinkholes, it develops as a larger-scale, gentler and structurally distinct depression. The location of new sinkholes and uvalas shows a marked shoreline-parallel migration with time, followed by a marked shoreline-perpendicular (i.e. seaward) growth with time. These observations are consistent with theoretical predictions of karstification controlled by a laterally migrating interface between saturated and undersaturated groundwater, as induced by the 35 m fall in the Dead Sea water level since 1967. More generally, our observations indicate that uvalas and the sinkhole populations within them, although morphometrically distinct, can develop near-synchronously by subsidence in response to subsurface erosion

Synthese et carte sismotectonique des pays de la bordure orientale de la Mediterranee : sismicite du systeme de failles du Jourdain-Mer Morte

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Episodic Behavior of the Jordan Valley Section of the Dead Sea Fault Inferred from a 14-ka-Long Integrated Catalog of Large Earthquakes

International audienceThe continuous record of large surface-rupturing earthquakes along the Dead Sea fault brings unprecedented insights for paleoseismic and archaeoseismic research. In most recent studies, paleoseismic trenching documents the late Holocene faulting activity, while tectonic geomorphology addresses the long-term behavior (> 10 ka), with a tendency to smooth the effect of individual earthquake rupture events (M w > 7). Here, we combine historical, archaeological, and paleoseismic investigations to build a consolidated catalog of destructive surface-rupturing earthquakes for the last 14 ka along the left-lateral Jordan Valley fault segment. The 120-km-long fault segment limited to the north and the south by major pull-apart basins (the Hula and the Dead Sea, respectively) is mapped in detail and shows five subseg-ments with narrow stepovers (width < 3 km). We conducted quantitative geomor-phology along the fault, measured more than 20 offset drainages, excavated four trenches at two sites, and investigated archaeological sites with seismic damage in the Jordan Valley. Our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at Tell Saydiyeh, supplemented with a rich historical seismic record, document 12 surface-rupturing events along the fault segment with a mean interval of ∼1160 yr and an average 5 mm=yr slip rate for the last 25 ka. The most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr, with a median value of 790 yr, and suggests an episodic behavior for the Jordan Valley fault. Our study allows a better constraint of the seismic cycle and related short-term variations (late Holocene) versus long-term behavior (Holocene and late Pleistocene) of a major continental transform fault

The Complex Karst Dynamics of the Lisan Peninsula Revealed by 25 Years of DInSAR Observations. Dead Sea, Jordan.

The Dead Sea (DS) area is one of the best examples of the significant impact that the uncontrolled exploitation of natural resources may have on the territory and the environment. In the last decades, the DS territory faced a profound change as consequence of the human activities that interfered with the delicate equilibrium of its ecosystem. In the 1960s, the potash industries started to heavily exploit the salty-rich water of the DS, pumping huge amount of water in the desalinization ponds located in the southern section of the lake. Furthermore, most of the freshwater that was coming from the Jordan River and from the other main feeders was diverted for urban and agricultural purposes in the region and as far as the Negev desert, in southern Israel. This, in combination with the unique climate of the territory, characterized by high annual evaporation rates (1500 mm) and very low average annual precipitations (60 mm) resulted in a strong negative water balance that caused the water level to drop with increasing speed. The decline rate, calculated as 17 cm/yr in the period from 1930 to 1973, has reached 100 cm/yr and exceeded 120 cm/yr nowadays. In the last 40 years, the level dropped by 36 m (as of March 2017, the DS water level is at -431 m m.s.l.) and the lake shrunk by more than one-third. The consequent change in the hydrogeological settings of the entire basin caused the seaward and downward migration of the fresh/saline groundwater interface forcing the freshwater to flow through the underlying evaporite layers constituted mainly by salt and gypsum. Dissolution-related phenomena such as subsidence and sinkholes started to appear all along the DS shoreline bringing heavy damage to the territory, the infrastructures (bridges, roads, earthen dikes of the desalinization ponds) and the buildings (houses, hotels, resorts, factories). The most active subsidence occurs in the areas surrounding the Lisan Peninsula (LP), located in the southern part of the DS in Jordanian territory. The Peninsula is also characterized by uplifting areas mainly as consequence of the upward movement of the underlying Lisan salt diapir. This work presents and analyses the results obtained from Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques applied the monitoring of an area of about 18 km x 22 km that entirely covers the LP. The available SAR datasets consist of: 24 ERS-1/2 covering the period 06/1992-06/2000 and 31 ENVISAT covering 01/2003-06/2010, both acquired in C-band by the European Space Agency (ESA); 10 L-band ALOS PALSAR acquired by the Japan Aerospace Exploration Agency (JAXA) from 11/2007 to 02/2011; 20 X-band COSMO-SkyMed (CSK) for the period 12/2011-05/2014 acquired by the Italian Space Agency (ASI). Finally, we exploited 32 Sentinel-1A images acquired by ESA and covering the period 10/2014-05/2016. In addition, another Sentinel-1A dataset made of 30 images acquired in ascending geometry over the same period was processed and used to assess the predominant component of the movements in the area. The image processing has been carried out using the Small Baseline Subset (SBAS) technique. The removal of the topographic component of the phase was carried out using the Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM) with a resolution of 30 m x 30 m. All the datasets were multi-looked differently in order to obtain the same ground resolution with a pixel size of 20 m x 20 m. The areas along the shore that were exposed year by year by the DS lowering, were masked out in all the images using the -415 m m.s.l. contour line of the SRTM DEM, that refers to the water level in February 2000 at the time the DEM was produced. The deformation values calculated along the line of sight (LOS) of the satellites were projected to the vertical direction considering the incidence angle of each point measured with the different sensors. The novelty of this work comes from the integration of three different wavelenghts (X, C and L) to study the dynamics of a salt dome. Five displacement maps have been produced, carefully checked and then fused to provide a total cumulated map of the displacements in the area. The ground movements have been analysed by comparison with in-situ tectonic observations collected by various authors since the mid-1980s. The results show an increase in the displacement rates starting from the 2000. The uplift occurring in the north part of the peninsula is probably caused by the combination of different factors such as tectonic, diapirism, elastic rebound. Semi-circular depressions occur around minor uplifting areas in the southern part of the peninsula as consequence of the salt diapir upward movement. Furthermore, the study shows an episodic rising of the Lisan diapir. The Sentinel-1A satellite used in this study demonstrated its great potential as a tool for continuous monitoring activity over areas affected even by very fast displacements. The obtained results updated the knowledge of the complex karst dynamics in the Lisan Peninsula, and could be used as the starting point for further studies in the area

Subsidence et effondrements le long du littoral jordanien de la mer Morte : apports de la gravimétrie et de l'interférométrie radar différentielle

The Dead Sea shore is affected by major subsidence and sinkholes hazards due to the decrease of the sea level. The frequency of resulting accidents increased during the last four decades. Those phenomena could be at the origin of the catastrophic destruction of a major salt evaporation pond on 22 March 2000. In this paper, we show the main results of eight years of research in gravimetry and radar interferometry devoted to identify potentially hazardous areas, at different scales along the Jordanian Dead Sea coast, from the metric scale (gravimetric approach) to the kilometric one (interferometric approach). (C) 2003 Academie des sciences. Publie par Editions scientifiques et medicales Elsevier SAS. Tons droits reserves