TY - JOUR A1 - Hetenyi, Gyorgy A1 - Molinari, Irene A1 - Clinton, John A1 - Bokelmann, Gotz A1 - Bondar, Istvan A1 - Crawford, Wayne C. A1 - Dessa, Jean-Xavier A1 - Doubre, Cecile A1 - Friederich, Wolfgang A1 - Fuchs, Florian A1 - Giardini, Domenico A1 - Graczer, Zoltan A1 - Handy, Mark R. A1 - Herak, Marijan A1 - Jia, Yan A1 - Kissling, Edi A1 - Kopp, Heidrun A1 - Korn, Michael A1 - Margheriti, Lucia A1 - Meier, Thomas A1 - Mucciarelli, Marco A1 - Paul, Anne A1 - Pesaresi, Damiano A1 - Piromallo, Claudia A1 - Plenefisch, Thomas A1 - Plomerova, Jaroslava A1 - Ritter, Joachim A1 - Rumpker, Georg A1 - Sipka, Vesna A1 - Spallarossa, Daniele A1 - Thomas, Christine A1 - Tilmann, Frederik A1 - Wassermann, Joachim A1 - Weber, Michael A1 - Weber, Zoltan A1 - Wesztergom, Viktor A1 - Zivcic, Mladen A1 - Abreu, Rafael A1 - Allegretti, Ivo A1 - Apoloner, Maria-Theresia A1 - Aubert, Coralie A1 - Besancon, Simon A1 - de Berc, Maxime Bes A1 - Brunel, Didier A1 - Capello, Marco A1 - Carman, Martina A1 - Cavaliere, Adriano A1 - Cheze, Jerome A1 - Chiarabba, Claudio A1 - Cougoulat, Glenn A1 - Cristiano, Luigia A1 - Czifra, Tibor A1 - Danesi, Stefania A1 - Daniel, Romuald A1 - Dannowski, Anke A1 - Dasovic, Iva A1 - Deschamps, Anne A1 - Egdorf, Sven A1 - Fiket, Tomislav A1 - Fischer, Kasper A1 - Funke, Sigward A1 - Govoni, Aladino A1 - Groschl, Gidera A1 - Heimers, Stefan A1 - Heit, Ben A1 - Herak, Davorka A1 - Huber, Johann A1 - Jaric, Dejan A1 - Jedlicka, Petr A1 - Jund, Helene A1 - Klingen, Stefan A1 - Klotz, Bernhard A1 - Kolinsky, Petr A1 - Kotek, Josef A1 - Kuhne, Lothar A1 - Kuk, Kreso A1 - Lange, Dietrich A1 - Loos, Jurgen A1 - Lovati, Sara A1 - Malengros, Deny A1 - Maron, Christophe A1 - Martin, Xavier A1 - Massa, Marco A1 - Mazzarini, Francesco A1 - Metral, Laurent A1 - Moretti, Milena A1 - Munzarova, Helena A1 - Nardi, Anna A1 - Pahor, Jurij A1 - Pequegnat, Catherine A1 - Petersen, Florian A1 - Piccinini, Davide A1 - Pondrelli, Silvia A1 - Prevolnik, Snjezan A1 - Racine, Roman A1 - Regnier, Marc A1 - Reiss, Miriam A1 - Salimbeni, Simone A1 - Santulin, Marco A1 - Scherer, Werner A1 - Schippkus, Sven A1 - Schulte-Kortnack, Detlef A1 - Solarino, Stefano A1 - Spieker, Kathrin A1 - Stipcevic, Josip A1 - Strollo, Angelo A1 - Sule, Balint A1 - Szanyi, Gyongyver A1 - Szucs, Eszter A1 - Thorwart, Martin A1 - Ueding, Stefan A1 - Vallocchia, Massimiliano A1 - Vecsey, Ludek A1 - Voigt, Rene A1 - Weidle, Christian A1 - Weyland, Gauthier A1 - Wiemer, Stefan A1 - Wolf, Felix A1 - Wolyniec, David A1 - Zieke, Thomas T1 - The AlpArray seismic network BT - a large-scale european experiment to image the alpine orogen JF - Surveys in Geophysics N2 - The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth. KW - Seismology KW - Alps KW - Seismic network KW - Geodynamics KW - Seismic imaging KW - Mountain building Y1 - 2018 U6 - https://doi.org/10.1007/s10712-018-9472-4 SN - 0169-3298 SN - 1573-0956 VL - 39 IS - 5 SP - 1009 EP - 1033 PB - Springer CY - Dordrecht 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - GEN A1 - Jousset, Philippe A1 - Reinsch, Thomas A1 - Ryberg, Trond A1 - Blanck, Hanna A1 - Clarke, Andy A1 - Aghayev, Rufat A1 - Hersir, Gylfi P. A1 - Henninges, Jan A1 - Weber, Michael A1 - Krawczyk, Charlotte M. T1 - Dynamic strain determination using fibre-optic cables allows imaging of seismological and structural features T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space. Seismological techniques provide ground-motion data, whose accuracy depends on sensor characteristics and spatial distribution. Here we demonstrate that dynamic strain determination is possible with conventional fibre-optic cables deployed for telecommunication. Extending recently distributed acoustic sensing (DAS) studies, we present high resolution spatially un-aliased broadband strain data. We recorded seismic signals from natural and man-made sources with 4-m spacing along a 15-km-long fibre-optic cable layout on Reykjanes Peninsula, SW-Iceland. We identify with unprecedented resolution structural features such as normal faults and volcanic dykes in the Reykjanes Oblique Rift, allowing us to infer new dynamic fault processes. Conventional seismometer recordings, acquired simultaneously, validate the spectral amplitude DAS response between 0.1 and 100 Hz bandwidth. We suggest that the networks of fibre-optic telecommunication lines worldwide could be used as seismometers opening a new window for Earth hazard assessment and exploration. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 691 KW - North-America KW - fault zone KW - tomography KW - frequency Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-426770 IS - 691 ER -