The Impact of Lake-Level Fluctuation on Earthquake Recurrence Interval over Historical and Prehistorical Timescales: The Case of the Dead Sea

We review the impact of large historical lake water-level changes on seismicity via the stress field of the shallow crust where devastating earthquakes nucleate. A novel backward earthquake simulation presented in this chapter can be used to investigate the geological record for the past ten millennia (presented in this study) and even more. The simulation is based on a theoretical model, which explains the variability in the recurrence interval of strong earthquakes. We suggest that the water-level changes in ancient lakes located in tectonic depressions along the Dead Sea transform could contribute to the observed differences. It is found that the increase in the water level moderates the seismic recurrence interval. Based on this empirical correlation together with mechanical considerations, an additional indication is established regarding the water-level reconstruction and location of earthquakes in the Dead Sea area. This indication is based on simulated earthquakes, by superimposing the effective normal stress change due to the reconstructed water-level change on the estimated tectonic shear stress accumulated since the preceding seismic event

Stratigraphic record reveals contrasting roles of overflows and underflows over glacial cycles in a hypersaline lake (Dead Sea)

In lakes and oceans, links between modern sediment density flow processes and deposits preserved in long-term geological records are poorly understood. Consequently, it is unclear whether, and if so how, long-term climate changes affect the magnitude/frequency of sediment density flows. One approach to answering this question is to analyze a comprehensive geological record that comprises deposits that can be reliably linked to modern sediment flow processes. To address this question, we investigated the unique ICDP Core 5017-1 from the Dead Sea (the largest and deepest hypersaline lake on the Earth) depocenter covering MIS 7-1. Based on an understanding of modern sediment density flow processes in the lake, we link homogeneous muds in the core to overflows (surface flood plumes, ρflowρwater). Our dataset reveals (1) overflows are more prominent during interglacials, while underflows are more prominent during glacials; (2) orbital-scale climate changes affected the flow magnitude/frequency via changing salinity and density profile of lake brine, lake-level, and source materials

The First Catalog of Archaeomagnetic Directions From Israel With 4,000 Years of Geomagnetic Secular Variations

The large and well-studied archaeological record of Israel offers a unique opportunity for collecting high resolution archaeomagnetic data from the past several millennia. Here, we initiate the first catalog of archaeomagnetic directions from Israel, with data covering the past four millennia. The catalog consists of 76 directions, of which 47 fulfill quality selection criteria with Fisher precision parameter (k) ≥ 60, 95% cone of confidence (α95) < 6° and number of specimens per site (n) ≥ 8. The new catalog complements our published paleointensity data from the Levant and enables testing the hypothesis of a regional geomagnetic anomaly in the Levant during the Iron Age proposed by Shaar et al. (2016, 2017). Most of the archaeomagnetic directions show < 15° angular deviations from an axial dipole field. However, we observe in the tenth and ninth century BCE short intervals with field directions that are 19°-22° different from an axial dipole field and inclinations that are 20°-22° steeper than an axial dipole field. The beginning of the first millennium BCE is also characterized with fast secular variation rates. The new catalog provides additional support to the Levantine Iron Age Anomaly hypothesis

Orbital- and Millennial-Scale Changes in Lake-Levels Facilitate Earthquake-Triggered Mass Failures in the Dead Sea Basin

Acknowledgments The authors appreciate the editor L. Flesch for handling our manuscript, Ed Pope and Sebastian Cardona for constructive reviews. This research was supported by the Austrian Science Fund (FWF): M 2817 to Y. Lu and P30285-N34 to J. Moernaut, the University of Liege under Special Funds for Research, IPD-STEMA Program (R.DIVE.0899-J-F-G to Y. Lu), the Israel Science Foundation (#1645/19 to S. Marco and #1093/10 to R. Bookman), and the ICDP. A.A. is indebted to the Helmholtz Virtual Institute DESERVE for support. The authors thank C. Daxer for help modeling the Kernel Density and Nadav Wetzler for discussion.Peer reviewedPublisher PD

A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin

Acknowledgments The authors appreciate the editor Lucy Flesch for handling our manuscript, Stefano Vitale and Alina Polonia for constructive reviews. This research was supported by the University of Liege under Special Funds for Research, IPD‐STEMA Program (R.DIVE.0899‐J‐F‐G to Y. Lu), Austrian Science Fund (FWF: M 2817 to Y. Lu), the DESERVE Virtual Institute of the Helmholtz Association (to A. Agnon), the Israel Science Foundation (#1093/10 to R.Bookman and #1645/19 to S.Marco), and the ICDP.Peer reviewedPublisher PD

Estimation of Low-Velocity Landfill Thickness with Multi-Method Seismic Surveys

Conventional geophysical methods are suitable for estimating the thicknesses of subsoil layers. By combining several geophysical methods, the uncertainties can be assessed. Hence, the reliability of the results increases with a more accurate engineering solution. To estimate the base of an abandoned landfill, we collected data using classical approaches: high-resolution seismic reflection and refraction, with more modern methods including passive surface wave analysis and horizontal-to-vertical spectral ratio (HVSR) measurements. To evaluate the thickness of the landfill, three different datasets were acquired along each of the two seismic lines, and five different processing methods were applied for each of the two arrays. The results of all the classical methods indicate very consistent correlations and mostly converge to clear outcomes. However, since the shear wave velocity of the landfill is relatively low (<150 (m/s)), the uncertainty of the HVSR results is significant. All these methods are engineering-oriented, environmentally friendly, and relatively low-cost. They may be jointly interpreted to better assess uncertainties and therefore enable an efficient solution for environmental or engineering purposes

The oceanic crust in 3D: Paleomagnetic reconstruction in the Troodos ophiolite gabbro

The Troodos complex, Cyprus, provides an opportunity to study the structural configuration along a fossil intersection of a spreading axis and a transform fault. We complement studies at Troodos that have reconstructed the brittle deformation of the upper crust by new paleomagnetic data from the gabbro suite. The gabbro suite is exposed at the extinct spreading axis continuing the Solea graben toward the intersection with the fossil Arakapas oceanic transform. This is a unique exposure of deep crustal rocks formed at both an inside-corner and an outside-corner of a ridge-transform intersection. Remanence directions from gabbros (23 sites) were used as indicators for rigid body rotation. The spatial distribution of rotation axes allow recognition of three regions to which deformation is partitioned: 1) a western region (outside corner) that experienced primarily tilt about horizontal axis 2) a central region with minor rotation and, 3) an eastern area (inside corner) where vertical axis rotations are dominant. The absence of significant rotation in the 6 km-wide central domain together with its location between the inside- and the outside corner uncover the root of a fossil axial volcanic zone, a zone sufficiently hot so the upper crust can decouple from the substrate. Clockwise rotation in the gabbro increases from the axial zone eastward, similar to that in the overlying dikes, indicating coupling of the lower crust with the brittle upper oceanic crust. The transition from the decoupled layers of sheeted dikes and gabbro in the axial zone to the dikes-gabbro coupling in the inside corner is in keeping with deepening of the brittle-ductile transition from the dike-gabbro boundary into the lower crust away from the axial zone. Our conclusions are consistent with one of the previous reconstructions in which the Solea spreading axis was orthogonal to the Arakapas trunsform fault, and with recent studies of the present-day lower oceanic crust. However, the newly inferred surface trace of the Solea spreading axis is further to the east, probably reflecting the tilt of axial upper crust rotated blocks. (c) 2006 Elsevier B.V. All rights reserved

An improved evaluation of the seismic/geodetic deformation-rate ratio for the Zagros Fold-and-Thrust collisional belt

This article has been accepted for publication in Geophysical Journal International ©: The Authors 2018. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.We present an improved picture of the ongoing crustal deformation field for the Zagros Fold-and-Thrust Belt continental collision zone by using an extensive combination of both novel and published GPS observations. The main results define the significant amount of oblique Arabia–Eurasia convergence currently being absorbed within the Zagros: right-lateral shear along the NW trending Main Recent fault in NW Zagros and accommodated between fold-and-thrust structures and NS right-lateral strike-slip faults on Southern Zagros. In addition, taking into account the 1909–2016 instrumental seismic catalogue, we provide a statistical evaluation of the seismic/geodetic deformation-rate ratio for the area. On Northern Zagros and on the Turkish–Iranian Plateau, a moderate to large fraction (∼49 and >60 per cent, respectively) of the crustal deformation occurs seismically. On the Sanandaj–Sirjan zone, the seismic/geodetic deformation-rate ratio suggests that a small to moderate fraction (<40 per cent) of crustal deformation occurs seismically; locally, the occurrence of large historic earthquakes (M ≥ 6) coupled with the high geodetic deformation, could indicate overdue M ≥ 6 earthquakes. On Southern Zagros, aseismic strain dominates crustal deformation (the ratio ranges in the 15–33 per cent interval). Such aseismic deformation is probably related to the presence of the weak evaporitic Hormuz Formation which allows the occurrence of large aseismic motion on both subhorizontal faults and surfaces of décollement. These results, framed into the seismotectonic framework of the investigated region, confirm that the fold-and-thrust-dominated deformation is driven by buoyancy forces; by contrast, the shear-dominated deformation is primary driven by plate stresses.Published194-2092T. Deformazione crostale attivaJCR Journa

Localised and distributed deformation in the lithosphere: Modelling the Dead Sea region in 3 dimensions

International audienceThe Earth's lithosphere behaves as a strain softening elasto-plastic material. In the laboratory, such materials are known to deform in a brittle or a ductile manner depending on the applied geometric boundary conditions. In the lithosphere however, the importance of boundary conditions in controlling the deformation style has been largely ignored. Under general boundary conditions, both laboratory and field scale observations show that only part of the deformation can localise on through going faults while the rest must remain distributed in 'process zones' where spatially varying shear directions inhibit localisation. Conventional modelling methods (finite difference, finite or discrete elements) use rheologies deduced from laboratory experiments that are not constrained as a function of the geometry of the applied boundary conditions. In this paper, we propose an alternative modelling method that is based on the use of an appropriate distribution of dislocation sources to create the deformation field. This approach, because it does not rely on integrating differential equations from more or less well-constrained boundary conditions, does not require making assumptions on the parameters controlling the level and distribution of stresses within the lithosphere. It only supposes that strain accumulates linearly away from the dislocation singularities satisfying the compatibility equations. We verify that this model explains important and hitherto unexplained features of the topography of the Dead Sea region. Following the idea that strain can only localise under specific conditions as inferred from laboratory and field scale observations, we use our model of deformation to predict where deformation can localise and where it has to remain distributed. We find that ~ 65% of the deformation in the Dead Sea region can localise on kinematically stable through-going strike-slip faults while the remaining ~ 35% has to remain distributed. Observations suggest that distributed deformation occurs at stress levels that can be ten times greater than that associated with motion on well-localised faults. Thus, although only representing a minor part of the total deformation, distributed deformation should provide the greatest source of resistance to motion along this part of the Levant plate. These results can change dramatically our view of the behaviour of this and other plate boundaries. If the lithosphere can be regarded as a strain softening elasto-plastic material then similar behaviour should occur throughout, with important implications not only for its mechanical behaviour, but also for heat generation and related issues like metamorphism or magma genesis