TY  - JOUR
A1  - Mohsen, Ayman
A1  - Kind, Rainer
A1  - Sobolev, Stephan Vladimir
A1  - Weber, Michael
T1  - Thickness of the lithosphere east of the Dead Sea Transform
JF  - Geophysical journal international
N2  - We use the S receiver function method to study the lithosphere at the Dead Sea Transform (DST). A temporary network of 22 seismic broad-band stations was operated on both sides of the DST from 2000 to 2001 as part of the DESERT project. We also used data from six additional permanent broad-band seismic stations at the DST and in the surrounding area, that is, in Turkey, Saudi Arabia, Egypt and Cyprus. Clear S-to-P converted phases from the crust-mantle boundary (Moho) and a deeper discontinuity, which we interpret as lithosphere-asthenosphere boundary (LAB) have been observed. The Moho depth (30-38 km) obtained from S receiver functions agrees well with the results from P receiver functions and other geophysical data. We observe thinning of the lithosphere on the eastern side of the DST from 80 km in the north of the Dead Sea to about 65 km at the Gulf of Aqaba. On the western side of the DST, the few data indicate a thin LAB of about 65 km. For comparison, we found a 90-km-thick lithosphere in eastern Turkey and a 160-km-thick lithosphere under the Arabian shield, respectively. These observations support previous suggestions, based on xenolith data, heat flow observations, regional uplift history and geodynamic modelling, that the lithosphere around DST has been significantly thinned in the Late Cenozoic, likely following rifting and spreading of the Red Sea.
KW  - Dead Sea Transform
KW  - S receiver functions
KW  - thickness of the lithosphere
Y1  - 2006
U6  - https://doi.org/10.1111/j.1365-246X.2006.03185.x
SN  - 0956-540X
SN  - 1365-246X
VL  - 167
IS  - 2
SP  - 845
EP  - 852
PB  - Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kottmeier, Christoph
A1  - Agnon, Amotz
A1  - Al-Halbouni, Djamil
A1  - Alpert, Pinhas
A1  - Corsmeier, Ulrich
A1  - Dahm, Torsten
A1  - Eshel, Adam
A1  - Geyer, Stefan
A1  - Haas, Michael
A1  - Holohan, Eoghan
A1  - Kalthoff, Norbert
A1  - Kishcha, Pavel
A1  - Krawczyk, Charlotte
A1  - Lati, Joseph
A1  - Laronne, Jonathan B.
A1  - Lott, Friederike
A1  - Mallast, Ulf
A1  - Merz, Ralf
A1  - Metzger, Jutta
A1  - Mohsen, Ayman
A1  - Morin, Efrat
A1  - Nied, Manuela
A1  - Roediger, Tino
A1  - Salameh, Elias
A1  - Sawarieh, Ali
A1  - Shannak, Benbella
A1  - Siebert, Christian
A1  - Weber, Michael
T1  - New perspectives on interdisciplinary earth science at the Dead Sea: The DESERVE project
JF  - The science of the total environment : an international journal for scientific research into the environment and its relationship with man
N2  - The Dead Sea region has faced substantial environmental challenges in recent decades, including water resource scarcity, similar to 1 m annual decreases in the water level, sinkhole development, ascending-brine freshwater pollution, and seismic disturbance risks. Natural processes are significantly affected by human interference as well as by climate change and tectonic developments over the long term. To get a deep understanding of processes and their interactions, innovative scientific approaches that integrate disciplinary research and education are required. The research project DESERVE (Helmholtz Virtual Institute Dead Sea Research Venue) addresses these challenges in an interdisciplinary approach that includes geophysics, hydrology, and meteorology. The project is implemented by a consortium of scientific institutions in neighboring countries of the Dead Sea (Israel, Jordan, Palestine Territories) and participating German Helmholtz Centres (KIT, GFZ, UFZ). A new monitoring network of meteorological, hydrological, and seismic/geodynamic stations has been established, and extensive field research and numerical simulations have been undertaken. For the first time, innovative measurement and modeling techniques have been applied to the extreme conditions of the Dead Sea and its surroundings. The preliminary results show the potential of these methods. First time ever performed eddy covariance measurements give insight into the governing factors of Dead Sea evaporation. High-resolution bathymetric investigations reveal a strong correlation between submarine springs and neo-tectonic patterns. Based on detailed studies of stratigraphy and borehole information, the extension of the subsurface drainage basin of the Dead Sea is now reliably estimated. Originality has been achieved in monitoring flash floods in an arid basin at its outlet and simultaneously in tributaries, supplemented by spatio-temporal rainfall data. Low-altitude, high resolution photogrammetry, allied to satellite image analysis and to geophysical surveys (e.g. shear-wave reflections) has enabled a more detailed characterization of sinkhole morphology and temporal development and the possible subsurface controls thereon. All the above listed efforts and scientific results take place with the interdisciplinary education of young scientists. They are invited to attend joint thematic workshops and winter schools as well as to participate in field experiments. (C) 2015 The Authors. Published by Elsevier B.V.
KW  - Climate
KW  - Water balance
KW  - Flash floods
KW  - Seismicity
KW  - Sinkholes
KW  - Education
Y1  - 2016
U6  - https://doi.org/10.1016/j.scitotenv.2015.12.003
SN  - 0048-9697
SN  - 1879-1026
VL  - 544
SP  - 1045
EP  - 1058
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Feld, Christian
A1  - Mechie, James
A1  - Hübscher, Christian
A1  - Hall, Jeremy
A1  - Nicolaides, Stelios
A1  - Gurbuz, Cemil
A1  - Bauer, Klaus
A1  - Louden, Keith
A1  - Weber, Michael
T1  - Crustal structure of the eratosthenes seamount, cyprus and S. Turkey from an amphibian wide-angle seismic profile
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - In 2010, project CoCoCo (incipient COntinent-COntinent COllision) recorded a 650 km long amphibian N-S wide-angle seismic profile, extending from the Anatolian plateau across southern Turkey and Cyprus to just south of the Eratosthenes Seamount (ESM). The aim of the project is to reveal the impact of the transition from subduction to continent-continent collision of Africa with Anatolia. Arrival picking, finite-differences ray-tracing and inversion of the offshore and on-offshore data produced a tomographic model across southern Cyprus, the accretionary wedge and the ESM. The main features of this model are (1) crustal P-velocities predominantly lower than 6.5 km/s beneath the ESM, (2) crustal thickness between 28 and 37 km, (3) an upper crustal reflection at 5 km depth beneath the ESM, (4) the likely presence of oceanic crust south of the ESM and a transform margin north of it and (5) a 12 km thick ophiolite sequence on Cyprus. Land shots on Turkey, also recorded on Cyprus, gravity data and geological and previous seismic investigations allow to derive a layered velocity model beneath Anatolia and the northern part of Cyprus. The main features of this model are (1) Moho depths of 38–45 km beneath the Anatolian plateau, (2) an upper and lower crust with large lateral changes in velocity and thickness, (3) a north-dipping subducting plate below Cyprus with a steepening of the dip-angle of the plate at about 45 km depth. Thus, the wide-angle seismic and gravity data provide detailed insights into the 2-D geometry and velocity structures associated with the Cyprus Arc collision zone. Finally, integrated analysis of the geophysics and geology allows a comprehensive interpretation of the crustal structure related to the collision process.
KW  - Controlled source seismology
KW  - Subduction zone processes
KW  - Continental margins: convergent
KW  - Crustal structure
KW  - Europe
KW  - Gravity anomalies and Earth structure
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2017.02.003
SN  - 0040-1951
SN  - 1879-3266
VL  - 700
SP  - 32
EP  - 59
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Fromm, T.
A1  - Jokat, W.
A1  - Ryberg, T.
A1  - Behrmann, Jan H.
A1  - Haberland, C.
A1  - Weber, Michael
T1  - The onset of Walvis Ridge: Plume influence at the continental margin
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - The opening of the South Atlantic is a classical example for a plume related continental breakup. Flood basalts are present on both conjugate margins as well as aseismic ridges connecting them with the current plume location at Tristan da Cunha. To determine the effect of the proposed plume head on the continental crust, we acquired wide-angle seismic data at the junction of the Walvis Ridge with the African continent and modelled the P-wave velocity structure in a forward approach. The profile extends 430 km along the ridge and continues onshore to a length of 720 km. Crustal velocities beneath the Walvis Ridge vary between 5.5 km/s and 7.0 km/s, a typical range for oceanic crust. The crustal thickness of 22 km, however, is approximately three times larger than of normal oceanic crust. The continent-ocean transition is characterized by 30 km thick crust with strong lateral velocity variations in the upper crust and a high-velocity lower crust (HVLC), where velocities reach up to 7.5 km/s. The HVLC is 100 to 130 km wider at the Walvis Ridge than it is farther south, and impinges onto the continental crust of the Kaoko fold belt. Such high seismic velocities indicate Mg-rich igneous material intruded into the continental crust during the initial rifting stage. However, the remaining continental crust seems unaffected by intrusions and the root of the 40 km-thick crust of the Kaoko belt is not thermally abraded. We conclude that the plume head did not modify the continental crust on a large scale, but caused rather local effects. Thus, it seems unlikely that a plume drove or initiated the breakup process. We further propose that the plume already existed underneath the continent prior to the breakup, and ponded melt erupted at emerging rift structures providing the magma for continental flood basalts. (C) 2017 Elsevier B.V. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2017.03.011
SN  - 0040-1951
SN  - 1879-3266
VL  - 716
SP  - 90
EP  - 107
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ryberg, Trond
A1  - Braeuer, Benjamin
A1  - Weber, Michael
T1  - Upper mantle structure at Walvis Ridge from P-n tomography
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - Passive continental margins offer the unique opportunity to study the processes involved in continental extension and break-up. Within the LISPWAL (Llthospheric Structure of the Namibian continental Passive margin at the intersection with the Walvis Ridge from amphibious seismic investigations) project, combined on- and offshore seismic experiments were designed to characterize the Southern African passive margin at the Walvis Ridge in northern Namibia. In addition to extensive analysis of the crustal structures, we carried out seismic investigations targeting the velocity structure of the upper mantle in the landfall region of the Walvis Ridge with the Namibian coast. Upper mantle P-n travel time tomography from controlled source, amphibious seismic data was used to investigate the sub-Moho upper mantle seismic velocity. We succeeded in imaging upper mantle structures potentially associated with continental break-up and/or the Tristan da Cunha hotspot track. We found mostly coast-parallel sub-Moho velocity anomalies, interpreted as structures which were created during Gondwana break-up. (C)2016 Published by Elsevier B.V.
KW  - Seismic investigations
KW  - P-n tomography
KW  - passive continental margin
KW  - Gondwana break-up
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2016.08.009
SN  - 0040-1951
SN  - 1879-3266
VL  - 716
SP  - 121
EP  - 129
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kastle, Emanuel D.
A1  - Weber, Michael
A1  - Krüger, Frank
T1  - Complex Deep Structure of the African Low-Velocity Zone
JF  - Bulletin of the Seismological Society of America
N2  - We use recently deployed seismological arrays in Africa to sample a 2D cross section through the mantle down to the core-mantle boundary (CMB). By making use of travel-time residuals of S, ScS, and SKS phases, a new shear-velocity model of the African low-velocity zone (ALVZ) is derived. Our model suggests between 1.2% shear-velocity reduction at the top and 5% at the bottom with respect to 1D reference models. The average reduction over the whole low-velocity zone (LVZ) amounts to 2% in the presented model and is therefore about twice as strong as values found in global tomographic models. The top of the LVZ reaches up to 1200-km depth, and its lateral extent at the CMB is about 35 degrees. We propose the existence of a gap of 300 km, splitting the structure into two blocks. Our results are based on remarkable differences in SK(K) S travel-time residuals over a few degrees distance. The complexity of the structure could provide a key to an improved understanding of the deep-mantle LVZ dynamics and composition by comparison to geodynamic models. The gap in the model might suggest that the 2D cross section is cutting through a 3D indentation in the boundary of the ALVZ but may also be interpreted as a sign of two individual plumes, rather than one large homogeneous upwelling.
Y1  - 2017
U6  - https://doi.org/10.1785/0120160215
SN  - 0037-1106
SN  - 1943-3573
VL  - 107
SP  - 1688
EP  - 1703
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Zang, Arno
A1  - Stephansson, Ove
A1  - Stenberg, Leif
A1  - Plenkers, Katrin
A1  - von Specht, Sebastian
A1  - Milkereit, Claus
A1  - Schill, Eva
A1  - Kwiatek, Grzegorz
A1  - Dresen, Georg
A1  - Zimmermann, Günter
A1  - Dahm, Torsten
A1  - Weber, Michael
T1  - Hydraulic fracture monitoring in hard rock at 410 m depth with an advanced fluid-injection protocol and extensive sensor array
JF  - Geophysical journal international
N2  - In this paper, an underground experiment at the Aspo Hard Rock Laboratory (HRL) is described. Main goal is optimizing geothermal heat exchange in crystalline rock mass at depth by multistage hydraulic fracturing with minimal impact on the environment, that is, seismic events. For this, three arrays with acoustic emission, microseismicity and electromagnetic sensors are installed mapping hydraulic fracture initiation and growth. Fractures are driven by three different water injection schemes (continuous, progressive and pulse pressurization). After a brief review of hydraulic fracture operations in crystalline rock mass at mine scale, the site geology and the stress conditions at Aspo HRL are described. Then, the continuous, single-flow rate and alternative, multiple-flow rate fracture breakdown tests in a horizontal borehole at depth level 410 m are described together with the monitoring networks and sensitivity. Monitoring results include the primary catalogue of acoustic emission hypocentres obtained from four hydraulic fractures with the in situ trigger and localizing network. The continuous versus alternative water injection schemes are discussed in terms of the fracture breakdown pressure, the fracture pattern from impression packer result and the monitoring at the arrays. An example of multistage hydraulic fracturing with several phases of opening and closing of fracture walls is evaluated using data from acoustic emissions, seismic broad-band recordings and electromagnetic signal response. Based on our limited amount of in situ tests (six) and evaluation of three tests in Avro granodiorite, in the multiple-flow rate test with progressively increasing target pressure, the acoustic emission activity starts at a later stage in the fracturing process compared to the conventional fracturing case with continuous water injection. In tendency, also the total number and magnitude of acoustic events are found to be smaller in the progressive treatment with frequent phases of depressurization.
KW  - Geomechanics
KW  - Fracture and flow
KW  - Broad-band seismometers
Y1  - 2016
SN  - 0956-540X
SN  - 1365-246X
VL  - 208
SP  - 790
EP  - 813
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Planert, Lars
A1  - Behrmann, Jan H.
A1  - Jokat, Wilfried
A1  - Fromm, Tanja
A1  - Ryberg, Trond
A1  - Weber, Michael
A1  - Haberland, Christian
T1  - The wide-angle seismic image of a complex rifted margin, offshore North Namibia: Implications for the tectonics of continental breakup
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - Voluminous magmatism during the South Atlantic opening has been considered as a classical example for plume related continental breakup. We present a study of the crustal structure around Walvis Ridge, near the intersection with the African margin. Two wide-angle seismic profiles were acquired. One is oriented NNW–SSE, following the continent–ocean transition and crossing Walvis Ridge. A second amphibious profile runs NW–SE from the Angola Basin into continental Namibia. At the continent–ocean boundary (COB) the mafic crust beneath Walvis Ridge is up to 33 km thick, with a pronounced high-velocity lower crustal body. Towards the south there is a smooth transition to 20–25 km thick crust underlying the COB in the Walvis Basin, with a similar velocity structure, indicating a gabbroic lower crust with associated cumulates at the base. The northern boundary of Walvis Ridge towards the Angola Basin shows a sudden change to oceanic crust only 4–6 km thick, coincident with the projection of the Florianopolis Fracture Zone, one of the most prominent tectonic features of the South Atlantic ocean basin. In the amphibious profile the COB is defined by a sharp transition from oceanic to rifted continental crust, with a magmatic overprint landward of the intersection of Walvis Ridge with the Namibian margin. The continental crust beneath the Congo Craton is 40 km thick, shoaling to 35 km further SE. The velocity models show that massive high-velocity gabbroic intrusives are restricted to a narrow zone directly underneath Walvis Ridge and the COB in the south. This distribution of rift-related magmatism is not easily reconciled with models of continental breakup following the establishment of a large, axially symmetric plume in the Earth's mantle. Rift-related lithospheric stretching and associated transform faulting play an overriding role in locating magmatism, dividing the margin in a magma-dominated southern and an essentially amagmatic northern segment.
KW  - Wide-angle seismic
KW  - Crustal structure
KW  - Walvis Ridge
KW  - Hotspot
KW  - Rifted continental margin
KW  - South Atlantic
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2016.06.024
SN  - 0040-1951
SN  - 1879-3266
VL  - 716
SP  - 130
EP  - 148
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Giling, Darren P.
A1  - Staehr, Peter A.
A1  - Grossart, Hans-Peter
A1  - Andersen, Mikkel Rene
A1  - Boehrer, Bertram
A1  - Escot, Carmelo
A1  - Evrendilek, Fatih
A1  - Gomez-Gener, Lluis
A1  - Honti, Mark
A1  - Jones, Ian D.
A1  - Karakaya, Nusret
A1  - Laas, Alo
A1  - Moreno-Ostos, Enrique
A1  - Rinke, Karsten
A1  - Scharfenberger, Ulrike
A1  - Schmidt, Silke R.
A1  - Weber, Michael
A1  - Woolway, R. Iestyn
A1  - Zwart, Jacob A.
A1  - Obrador, Biel
T1  - Delving deeper: Metabolic processes in the metalimnion of stratified lakes
JF  - Limnology and oceanography
N2  - Many lakes exhibit seasonal stratification, during which they develop strong thermal and chemical gradients. An expansion of depth-integrated monitoring programs has provided insight into the importance of organic carbon processing that occurs below the upper mixed layer. However, the chemical and physical drivers of metabolism and metabolic coupling remain unresolved, especially in the metalimnion. In this depth zone, sharp gradients in key resources such as light and temperature co-occur with dynamic physical conditions that influence metabolic processes directly and simultaneously hamper the accurate tracing of biological activity. We evaluated the drivers of metalimnetic metabolism and its associated uncertainty across 10 stratified lakes in Europe and North America. We hypothesized that the metalimnion would contribute highly to whole-lake functioning in clear oligotrophic lakes, and that metabolic rates would be highly variable in unstable polymictic lakes. Depth-integrated rates of gross primary production (GPP) and ecosystem respiration (ER) were modelled from diel dissolved oxygen curves using a Bayesian approach. Metabolic estimates were more uncertain below the epilimnion, but uncertainty was not consistently related to lake morphology or mixing regime. Metalimnetic rates exhibited high day-to-day variability in all trophic states, with the metalimnetic contribution to daily whole-lake GPP and ER ranging from 0% to 87% and < 1% to 92%, respectively. Nonetheless, the metalimnion of low-nutrient lakes contributed strongly to whole-lake metabolism on average, driven by a collinear combination of highlight, low surface-water phosphorous concentration and high metalimnetic volume. Consequently, a single-sensor approach does not necessarily reflect whole-ecosystem carbon dynamics in stratified lakes.
Y1  - 2017
U6  - https://doi.org/10.1002/lno.10504
SN  - 0024-3590
SN  - 1939-5590
VL  - 62
SP  - 1288
EP  - 1306
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Weber, Michael
A1  - Scholz, Denis
A1  - Schröder-Ritzrau, Andrea
A1  - Deininger, Michael
A1  - Spötl, Christoph
A1  - Lugli, Federico
A1  - Mertz-Kraus, Regina
A1  - Jochum, Klaus Peter
A1  - Fohlmeister, Jens Bernd
A1  - Stumpf, Cintia F.
A1  - Riechelmann, Dana F. C.
T1  - Evidence of warm and humid interstadials in central Europe during early MISSUE 3 revealed by a multi-proxy speleothem record
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - Marine Isotope Stage 3 (MIS 3, 57-27 ka) was characterised by numerous rapid climate oscillations (i.e., Dansgaard-Oeschger (D/O-) events), which are reflected in various climate archives. So far, MIS 3 speleothem records from central Europe have mainly been restricted to caves located beneath temperate Alpine glaciers or close to the Atlantic Ocean. Thus, MIS 3 seemed to be too cold and dry to enable speleothem growth north of the Alps in central Europe. Here we present a new speleothem record from Bunker Cave, Germany, which shows two distinct growth phases from 52.0 (+0.8, -0.5) to 50.9 (+0.6, -1.3) ka and 473 (+1.0, -0.6) to 42.8 (+/- 0.9) ka, rejecting this hypothesis. These two growth phases potentially correspond to the two warmest and most humid phases in central Europe during MIS 3, which is confirmed by pollen data from the nearby Eifel. The hiatus separating the two phases is associated with Heinrich stadial 5 (HS 5), although the growth stop precedes the onset of HS 5. The first growth phase is characterised by a fast growth rate, and Mg concentrations and Sr isotope data suggest high infiltration and the presence of soil cover above the cave. The second growth phase was characterised by drier, but still favourable conditions for speleothem growth. During this phase, the delta C-13 values show a significant decrease associated with D/O-event 12. The timing of this shift is in agreement with other MIS 3 speleothem data from Europe and Greenland ice core data. (C) 2018 Elsevier Ltd. All rights reserved.
KW  - Speleothems
KW  - Pleistocene
KW  - Palaeoclimatology
KW  - Europe
KW  - Dansgaard-Oeschger event
KW  - Marine isotope stage 3
KW  - Bunker cave
KW  - Multi-proxy approach
KW  - U-Th series
Y1  - 2018
U6  - https://doi.org/10.1016/j.quascirev.2018.09.045
SN  - 0277-3791
VL  - 200
SP  - 276
EP  - 286
PB  - Elsevier
CY  - Oxford
ER  -