@article{JoziNajafabadiHaberlandRybergetal.2021, author = {Jozi Najafabadi, Azam and Haberland, Christian and Ryberg, Trond and Verwater, Vincent F. and Breton, Eline le and Handy, Mark R. and Weber, Michael}, title = {Relocation of earthquakes in the southern and eastern Alps (Austria, Italy) recorded by the dense, temporary SWATH-D network using a Markov chain Monte Carlo inversion}, series = {Solid earth : SE ; an interaktive open access journal of the European Geosciences Union}, volume = {12}, journal = {Solid earth : SE ; an interaktive open access journal of the European Geosciences Union}, number = {5}, publisher = {Copernicus}, address = {G{\"o}ttingen}, organization = {AlpArray Working Grp, AlpArray SWATH-D Working Grp}, issn = {1869-9529}, doi = {10.5194/se-12-1087-2021}, pages = {1087 -- 1109}, year = {2021}, abstract = {In this study, we analyzed a large seismological dataset from temporary and permanent networks in the southern and eastern Alps to establish high-precision hypocenters and 1-D V-P and V-P/V-S models. The waveform data of a subset of local earthquakes with magnitudes in the range of 1-4.2 M-L were recorded by the dense, temporary SWATH-D network and selected stations of the AlpArray network between September 2017 and the end of 2018. The first arrival times of P and S waves of earthquakes are determined by a semi-automatic procedure. We applied a Markov chain Monte Carlo inversion method to simultaneously calculate robust hypocenters, a 1-D velocity model, and station corrections without prior assumptions, such as initial velocity models or earthquake locations. A further advantage of this method is the derivation of the model parameter uncertainties and noise levels of the data. The precision estimates of the localization procedure is checked by inverting a synthetic travel time dataset from a complex 3-D velocity model and by using the real stations and earthquakes geometry. The location accuracy is further investigated by a quarry blast test. The average uncertainties of the locations of the earthquakes are below 500m in their epicenter and similar to 1.7 km in depth. The earthquake distribution reveals seismicity in the upper crust (0-20 km), which is characterized by pronounced clusters along the Alpine frontal thrust, e.g., the Friuli-Venetia (FV) region, the Giudicarie-Lessini (GL) and Schio-Vicenza domains, the Austroalpine nappes, and the Inntal area. Some seismicity also occurs along the Periadriatic Fault. The general pattern of seismicity reflects head-on convergence of the Adriatic indenter with the Alpine orogenic crust. The seismicity in the FV and GL regions is deeper than the modeled frontal thrusts, which we interpret as indication for southward propagation of the southern Alpine deformation front (blind thrusts).}, language = {en} } @article{JoziNajafabadiHaberlandLeBretonetal.2022, author = {Jozi Najafabadi, Azam and Haberland, Christian and Le Breton, Eline and Handy, Mark R. and Verwater, Vincent F. and Heit, Benjamin and Weber, Michael}, title = {Constraints on crustal structure in the vicinity of the adriatic indenter (European Alps) from Vp and Vp/Vs local earthquake tomography}, series = {Journal of geophysical research : Solid earth}, volume = {127}, journal = {Journal of geophysical research : Solid earth}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1029/2021JB023160}, pages = {22}, year = {2022}, abstract = {In this study, 3-D models of P-wave velocity (Vp) and P-wave and S-wave ratio (Vp/Vs) of the crust and upper mantle in the Eastern and eastern Southern Alps (northern Italy and southern Austria) were calculated using local earthquake tomography (LET). The data set includes high-quality arrival times from well-constrained hypocenters observed by the dense, temporary seismic networks of the AlpArray AASN and SWATH-D. The resolution of the LET was checked by synthetic tests and analysis of the model resolution matrix. The small inter-station spacing (average of similar to 15 km within the SWATH-D network) allowed us to image crustal structure at unprecedented resolution across a key part of the Alps. The derived P velocity model revealed a highly heterogeneous crustal structure in the target area. One of the main findings is that the lower crust is thickened, forming a bulge at 30-50 km depth just south of and beneath the Periadriatic Fault and the Tauern Window. This indicates that the lower crust decoupled both from its mantle substratum as well as from its upper crust. The Moho, taken to be the iso-velocity contour of Vp = 7.25 km/s, agrees with the Moho depth from previous studies in the European and Adriatic forelands. It is shallower on the Adriatic side than on the European side. This is interpreted to indicate that the European Plate is subducted beneath the Adriatic Plate in the Eastern and eastern Southern Alps.}, language = {en} } @article{HaberlandHampeAutenriethetal.2019, author = {Haberland, Christian and Hampe, Oliver and Autenrieth, Marijke and Voss, Manja}, title = {Balaenoptera borealis Lesson, 1828}, series = {Mammalia}, volume = {83}, journal = {Mammalia}, number = {4}, publisher = {De Gruyter}, address = {Berlin}, issn = {0025-1461}, doi = {10.1515/mammalia-2017-0149}, pages = {343 -- 351}, year = {2019}, abstract = {The whereabouts of the Balaenoptera borealis holotype, the skeleton of a 1819 stranded specimen, have been unknown since the World War II (WWII). Due to nomenclatural confusion, deficient documentation, and finally WWII bombing, which destroyed predominantly cetacean material in the Museum fib Naturkunde Berlin (MfN), the type skeleton of the sei whale sank into oblivion. Construction activities enabled a recent search and study on the remaining whale material. Here, we provide evidence that the type specimen was not destroyed. On the basis of species-wide and individual characters of the type material such as the shape of cranial elements and the pattern of the maxillary foramina, we show that the skull and mandibles, the vertebral column (except the atlas), and the ribs of the holotype remain intact. Further evidence that these skeletal remains belong to the previously missing holotype is provided by the characteristics of the spine. In addition, we analyzed ancient DNA from bone samples and confirm they are B. borealis, and the occurrence of same mitochondrial haplotypes indicate that the bones belong to the same individual. Additionally, a blue inscription was discovered at the caudal epiphysis of a thoracic vertebra; historical research matched this inscription with the material belonging to the former Anatomical-Zootomical Museum, from which the holotype was once bought.}, language = {en} } @article{PlanertBehrmannJokatetal.2017, author = {Planert, Lars and Behrmann, Jan H. and Jokat, Wilfried and Fromm, Tanja and Ryberg, Trond and Weber, Michael and Haberland, Christian}, title = {The wide-angle seismic image of a complex rifted margin, offshore North Namibia: Implications for the tectonics of continental breakup}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {716}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-1951}, doi = {10.1016/j.tecto.2016.06.024}, pages = {130 -- 148}, year = {2017}, abstract = {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.}, language = {en} } @article{HaberlandRietbrockLangeetal.2006, author = {Haberland, Christian and Rietbrock, Andreas and Lange, Dietrich and Bataille, Klaus and Hofmann, S.}, title = {Interaction between forearc and oceanic plate at the south-central Chilean margin as seen in local seismic data}, series = {Geophysical research letters}, volume = {33}, journal = {Geophysical research letters}, number = {23}, publisher = {Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2006GL028189}, pages = {5}, year = {2006}, abstract = {We installed a dense, amphibious, temporary seismological network to study the seismicity and structure of the seismogenic zone in southern Chile between 37° and 39°S, the nucleation area of the great 1960 Chile earthquake. 213 local earthquakes with 14.754 onset times were used for a simultaneous inversion for the 1-D velocity model and precise earthquake locations. Relocated artificial shots suggest an accuracy of the earthquake hypocenter of about 1 km (horizontally) and 500 m (vertically). Crustal events along trench-parallel and transverse, deep-reaching faults reflect the interseismic transpressional deformation of the forearc crust due to the subduction of the Nazca plate. The transverse faults seems to accomplish differential lateral stresses between subduction zone segments. Many events situated in an internally structured, planar seismicity patch at 20 to 40 km depth near the coast indicate a stress concentration at the plate's interface at 38°S which might in part be induced by the fragmented forearc structure.}, language = {en} } @article{RybergHaberlandHaberlauetal.2015, author = {Ryberg, Trond and Haberland, Christian and Haberlau, Thomas and Weber, Michael H. and Bauer, Klaus and Behrmann, Jan H. and Jokat, Wilfried}, title = {Crustal structure of northwest Namibia: Evidence for plume-rift-continent interaction}, series = {Geology}, volume = {43}, journal = {Geology}, number = {8}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G36768.1}, pages = {739 -- 742}, year = {2015}, abstract = {The causes for the formation of large igneous provinces and hotspot trails are still a matter of considerable dispute. Seismic tomography and other studies suggest that hot mantle material rising from the core-mantle boundary (CMB) might play a significant role in the formation of such hotspot trails. An important area to verify this concept is the South Atlantic region, with hotspot trails that spatially coincide with one of the largest low-velocity regions at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to form during the separation of the South American and African continents at ca. 130 Ma as a consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to constrain processes of plume-lithosphere interaction and the formation of continental flood basalts (Parana and Etendeka continental flood basalts) and associated intrusive rocks. Our study identified a narrow region (<100 km) of high-seismic-velocity anomalies in the middle and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors connecting the high-velocity body with shallow crustal structures that we speculate to mark potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed massive but localized mafic intrusion into the lower crust results from similar-sized variations in the lithosphere (i.e., lithosphere thickness or preexisting structures).}, language = {en} } @article{OverduinHaberlandRybergetal.2015, author = {Overduin, Pier Paul and Haberland, Christian and Ryberg, Trond and Kneier, Fabian and Jacobi, Tim and Grigoriev, Mikhail N. and Ohrnberger, Matthias}, title = {Submarine permafrost depth from ambient seismic noise}, series = {Geophysical research letters}, volume = {42}, journal = {Geophysical research letters}, number = {18}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2015GL065409}, pages = {7581 -- 7588}, year = {2015}, abstract = {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.}, language = {en} } @article{FrommPlanertJokatetal.2015, author = {Fromm, T. and Planert, Lars and Jokat, Wilfried and Ryberg, Trond and Behrmann, Jan H. and Weber, Michael H. and Haberland, Christian}, title = {South Atlantic opening: A plume-induced breakup?}, series = {Geology}, volume = {43}, journal = {Geology}, number = {10}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G36936.1}, pages = {931 -- 934}, year = {2015}, abstract = {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.}, language = {en} } @article{BraeuerAschHofstetteretal.2014, author = {Braeuer, Benjamin and Asch, G{\"u}nter and Hofstetter, Rami and Haberland, Christian and Jaser, D. and El-Kelani, R. and Weber, Michael H.}, title = {Detailed seismicity analysis revealing the dynamics of the southern Dead Sea area}, series = {Journal of seismology}, volume = {18}, journal = {Journal of seismology}, number = {4}, publisher = {Springer}, address = {Dordrecht}, issn = {1383-4649}, doi = {10.1007/s10950-014-9441-4}, pages = {731 -- 748}, year = {2014}, abstract = {Within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. During 18 recording months, 648 events were detected. Based on an already published tomography study clustering, focal mechanisms, statistics and the distribution of the microseismicity in relation to the velocity models from the tomography are analysed. The determined b value of 0.74 leads to a relatively high risk of large earthquakes compared to the moderate microseismic activity. The distribution of the seismicity indicates an asymmetric basin with a vertical strike-slip fault forming the eastern boundary of the basin, and an inclined western boundary, made up of strike-slip and normal faults. Furthermore, significant differences between the area north and south of the Bokek fault were observed. South of the Bokek fault, the western boundary is inactive while the entire seismicity occurs on the eastern boundary and below the basin-fill sediments. The largest events occurred here, and their focal mechanisms represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. The vertical extension of the spatial and temporal cluster from February 2007 is interpreted as being related to the locking of the region around the Bokek fault. North of the Bokek fault similar seismic activity occurs on both boundaries most notably within the basin-fill sediments, displaying mainly small events with strike-slip mechanism and normal faulting in EW direction. Therefore, we suggest that the Bokek fault forms the border between the single transform fault and the pull-apart basin with two active border faults.}, language = {en} } @article{ValesDiasRioetal.2014, author = {Vales, Dina and Dias, Nuno A. and Rio, Ines and Matias, Luis and Silveira, Graca and Madeira, Jose and Weber, Michael H. and Carrilho, Fernando and Haberland, Christian}, title = {Intraplate seismicity across the Cape Verde swell: A contribution from a temporary seismic network}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {636}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-1951}, doi = {10.1016/j.tecto.2014.09.014}, pages = {325 -- 337}, year = {2014}, abstract = {We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008. The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antao and Sao Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antao, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde. The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} }