TY - JOUR A1 - Fromm, T. A1 - Planert, Lars A1 - Jokat, Wilfried A1 - Ryberg, Trond A1 - Behrmann, Jan H. A1 - Weber, Michael H. A1 - Haberland, Christian T1 - South Atlantic opening: A plume-induced breakup? JF - Geology N2 - Upwelling hot mantle plumes are thought to disintegrate continental lithosphere and are considered to be drivers of active continental breakup. The formation of the Walvis Ridge during the opening of the South Atlantic is related to a putative plume-induced breakup. We investigated the crustal structure of the Walvis Ridge (southeast Atlantic Ocean) at its intersection with the continental margin and searched for anomalies related to the possible plume head. The overall structure we identify suggests that no broad plume head existed during opening of the South Atlantic and anomalous mantle melting occurred only locally. We therefore question the importance of a plume head as a driver of continental breakup and further speculate that the hotspot was present before the rifting, leaving a track of kimberlites in the African craton. Y1 - 2015 U6 - https://doi.org/10.1130/G36936.1 SN - 0091-7613 SN - 1943-2682 VL - 43 IS - 10 SP - 931 EP - 934 PB - American Institute of Physics CY - Boulder 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 - TY - JOUR 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 JF - Nature Communications 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. Y1 - 2018 U6 - https://doi.org/10.1038/s41467-018-04860-y SN - 2041-1723 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kummerow, J. A1 - Kind, Rainer A1 - Oncken, Onno A1 - Giese, Peter A1 - Ryberg, Trond A1 - Wylegalla, Kurt A1 - Scherbaum, Frank T1 - A natural and controlled source seismic profile through the Eastern Alps : TRANSALP N2 - The combined passive and active seismic TRANSALP experiment produced an unprecedented high-resolution crustal image of the Eastern Alps between Munich and Venice. The European and Adriatic Mohos (EM and AM, respectively) are clearly imaged with different seismic techniques: near-vertical incidence reflections and receiver functions (RFs). The European Moho dips gently southward from 35 km beneath the northern foreland to a maximum depth of 55 km beneath the central part of the Eastern Alps, whereas the Adriatic Moho is imaged primarily by receiver functions at a relatively constant depth of about 40 km. In both data sets, we have also detected first-order Alpine shear zones, such as the Helvetic detachment, Inntal fault and SubTauern ramp in the north. Apart from the Valsugana thrust, receiver functions in the southern part of the Eastern Alps have also observed a north dipping interface, which may penetrate the entire Adriatic crust [Adriatic Crust Interface (ACI)]. Deep crustal seismicity may be related to the ACI. We interpret the ACI as the currently active retroshear zone in the doubly vergent Alpine collisional belt. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 ER - TY - JOUR A1 - Maercklin, Nils A1 - Bedrosian, Paul A. A1 - Haberland, Christian A1 - Ritter, O. A1 - Ryberg, Trond A1 - Weber, Michael H. A1 - Weckmann, Ute T1 - Characterizing a large shear-zone with seismic and magnetotelluric methods : the case of the Dead Sea Transform N2 - Seismic tomography, imaging of seismic scatterers, and magnetotelluric soundings reveal a sharp lithologic contrast along a similar to 10 km long segment of the Arava Fault (AF), a prominent fault of the southern Dead Sea Transform (DST) in the Middle East. Low seismic velocities and resistivities occur on its western side and higher values east of it, and the boundary between the two units coincides partly with a seismic scattering image. At 1 - 4 km depth the boundary is offset to the east of the AF surface trace, suggesting that at least two fault strands exist, and that slip occurred on multiple strands throughout the margin's history. A westward fault jump, possibly associated with straightening of a fault bend, explains both our observations and the narrow fault zone observed by others Y1 - 2005 SN - 0094-8276 ER - TY - JOUR A1 - Maercklin, Nils A1 - Haberland, Christian A1 - Ryberg, Trond A1 - Weber, Michael H. A1 - Bartov, Yosef T1 - Imaging the Dead Sea Transform with scattered seismic waves N2 - With controlled seismic sources and specifically designed receiver arrays, we image a subvertical boundary between two lithological blocks at the Arava Fault (AF) in the Middle East. The AF is the main strike-slip fault of the Dead Sea Transform (DST) in the segment between the Dead Sea and the Red Sea. Our imaging (migration) method is based on array beamforming and coherence analysis of P to P scattered seismic phases. We use a 1-D background velocity model and the direct P arrival as a reference phase. Careful resolution testing is necessary, because the target volume is irregularly sampled by rays. A spread function describing energy dispersion at localized point scatterers and synthetic calculations for large planar structures provides estimates of the resolution of the images. We resolve a 7 km long steeply dipping reflector offset roughly 1 km from the surface trace of the AF. The reflector can be imaged from about 1 km down to 4 km depth. Previous and ongoing studies in this region have shown a strong contrast across the fault: low seismic velocities and electrical resistivities to the west and high velocities and resistivities to the east of it. We therefore suggest that the imaged reflector marks the contrast between young sedimentary fill in the west and Precambrian rocks in the east. If correct, the boundary between the two blocks is offset about 1 km east of the current surface trace of the AF Y1 - 2004 SN - 0956-540X ER - TY - JOUR A1 - Overduin, Pier Paul A1 - Haberland, Christian A1 - Ryberg, Trond A1 - Kneier, Fabian A1 - Jacobi, Tim A1 - Grigoriev, Mikhail N. A1 - Ohrnberger, Matthias T1 - Submarine permafrost depth from ambient seismic noise JF - Geophysical research letters N2 - Permafrost inundated since the last glacial maximum is degrading, potentially releasing trapped or stabilized greenhouse gases, but few observations of the depth of ice-bonded permafrost (IBP) below the seafloor exist for most of the arctic continental shelf. We use spectral ratios of the ambient vibration seismic wavefield, together with estimated shear wave velocity from the dispersion curves of surface waves, for estimating the thickness of the sediment overlying the IBP. Peaks in spectral ratios modeled for three-layered 1-D systems correspond with varying thickness of the unfrozen sediment. Seismic receivers were deployed on the seabed around Muostakh Island in the central Laptev Sea, Siberia. We derive depths of the IBP between 3.7 and 20.7m15%, increasing with distance from the shoreline. Correspondence between expected permafrost distribution, modeled response, and observational data suggests that the method is promising for the determination of the thickness of unfrozen sediment. KW - submarine permafrost KW - ambient noise KW - Siberia KW - continental shelf Y1 - 2015 U6 - https://doi.org/10.1002/2015GL065409 SN - 0094-8276 SN - 1944-8007 VL - 42 IS - 18 SP - 7581 EP - 7588 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Paschke, Marco A1 - Stiller, Manfred A1 - Ryberg, Trond A1 - Weber, Michael H. T1 - The shallow P-velocity structure of the southern Dead Sea basin derived from near-vertical incidence reflection seismic data in project DESIRE JF - Geophysical journal international N2 - As a part of the DEad Sea Integrated REsearch (DESIRE) project a near-vertical incidence reflection (NVR) experiment with a profile length of 122 km was completed in spring 2006. The profile crossed the southern Dead Sea basin (DSB), a pull-apart basin due to the strike-slip motion along the Dead Sea Transform (DST). The DST with a total displacement of 107 km since about 18 Ma is part of a left-lateral fault system which connects the spreading centre in the Red Sea with the Taurus collision zone in Turkey over a distance of about 1100 km. The seismic experiment comprises 972 source locations and 1045 receiver locations. Each source was recorded by similar to 180 active receivers and a field data set with 175 000 traces was created. From this data set, 124 444 P-wave first-break traveltimes have been picked. With these traveltimes a tomographic inversion was carried out, resulting in a 2-D P-wave velocity model with a rms error of 20.9 ms. This model is dominated by a low-velocity region associated with the DSB. Within the DSB, the model shows clearly the position of the Lisan salt diapir, identified by a high-velocity zone. A further feature is an unexpected laterally low-velocity zone with P-velocities of 3 km s1 embedded in regions with 4 km s1 in the shallow part on the west side of the DSB. Another observation is an anticlinal structure west of the DSB interpretated to the related Syrian arc fold belt. KW - Tomography KW - Controlled source seismology KW - Transform faults Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-246X.2011.05270.x SN - 0956-540X VL - 188 IS - 2 SP - 524 EP - 534 PB - Wiley-Blackwell CY - Malden 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 - THES A1 - Ryberg, Trond T1 - Die Struktur des oberen Erdmantels und der Übergangszone Y1 - 1999 ER -