128 research outputs found

    Metabolic profile of complete spinal cord injury in pons and cerebellum: A 3T 1H MRS study

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    Abstract The aim of this exploratory study was the assessment of the metabolic profiles of persons with complete spinal cord injury (SCI) in three region-of-interests (pons, cerebellar vermis, and cerebellar hemisphere), with magnetic resonance spectroscopy, and their correlations to clinical scores. Group differences and association between metabolic and clinical scores were examined. Fifteen people with chronic SCI (cSCI), five people with subacute SCI (sSCI) and fourteen healthy controls were included. Group comparison between cSCI and HC showed lower total N-acetyl-aspartate (tNAA) in the pons (p‚ÄČ=‚ÄČ0.04) and higher glutathione (GSH) in the cerebellar vermis (p‚ÄČ=‚ÄČ0.02). Choline levels in the cerebellar hemisphere were different between cSCI and HC (p‚ÄČ=‚ÄČ0.02) and sSCI and HC (p‚ÄČ=‚ÄČ0.02). A correlation was reported for choline containing compounds (tCho) to clinical scores in the pons (rho‚ÄČ=‚ÄČ‚ąí¬†0.55, p‚ÄČ=‚ÄČ0.01). tNAA to total creatine (tNAA/tCr ratio) correlated to clinical scores in the cerebellar vermis (rho‚ÄČ=‚ÄČ0.61, p‚ÄČ=‚ÄČ0.004) and GSH correlated to the independence score in the cerebellar hemisphere (rho‚ÄČ=‚ÄČ0.56, p‚ÄČ=‚ÄČ0.01). The correlation of tNAA, tCr, tCho and GSH to clinical scores might be indicators on how well the CNS copes with the post-traumatic remodeling and might be further examined as outcome markers

    Kinematics and rifting processes of the Liguro-Provençal Basin, Western Mediterranean

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    The Liguro-Proven√ßal Basin, situated at the junction of the Northern Apennines and the Western Alps, formed due to the rollback subduction of the Adriatic-African plate underneath Europe and the subsequent upper plate extension in the Oligocene to early Miocene times. The opening of the basin was accompanied by the counter-clockwise rotation of the Corsica-Sardinia block relative to Europe until 16 Ma, with the basin widening towards the southwest. It remains controversial if the extension ever reached seafloor spreading with the production of oceanic crust, or whether it led to anomalously thin continental crust and/or to mantle exhumation. Although considered as tectonically inactive today, the Liguro-Proven√ßal Basin shows active seismicity, indicating compression and possible basin inversion (Thorwart et al. 2021). Thus it is crucial to better understand the opening of the basin and the tectonic inheritance due to rifting in order to interpret the present-day seismicity. To this end, we compiled existing geological and geophysical data, including recent data from the 4DMB project (‚ÄúMountain Building Processes in Four Dimensions‚ÄĚ), to constrain the crustal and sedimentary thicknesses throughout the basin. We focus specifically on two profiles in the NE (Corsica-Provence) and SW (Sardinia-Gulf of Lion) parts of the basin, along the opening direction of the basin. For each selected profile we calculated the average velocity using the kinematic reconstructions of Le Breton et al. (2021) and the amount of extension using an aerial balancing approach. We then compared these profiles and amounts of extension with results of coupled thermo-mechanical of asymmetric rifting and surface processes modelling using Aspect and Fastscape codes from Neuharth et al. (2022). The results of the thermo-mechanical modelling fit very well the present-day geometry of the rifted continental crust, with a wider hyper-extended rifted margin on the European and a narrower rifted margin on the Corsica-Sardinia side. Rifting migrated southeastward through time and seems to not have reached oceanic spreading nor mantle exhumation in the northeast part of the basin, as observed in the most recent seismic profile A401A-SMPL obtained within the 4DMB SPP project. Towards the southwest, the model confirms the presence of exhumed mantle, as proposed in previous study (Jolivet et al. 2015). The synthesis of geophysical data and thermomechanical modelling also fits very well in the existing kinematic reconstructions from 35 to 0 Ma of the Western Mediterranean, allowing us to infer the lateral extent of oceanic crust and exhumed mantle domains within the basin. Finally, present-day compressional seismicity seems to reactivate rift-related structures

    Extension Dynamics of the Northern Fonualei Rift and Spreading Center and the Southern Mangatolu Triple Junction in the Lau Basin at 16¬įS

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    Due to the complexity of 2D magnetic anomaly maps north of 18¬įS and the sparsity of seismic data, the tectonic evolution of the northern Lau Basin has not yet been unraveled. We use a multi-method approach to reconstruct the formation of the basin at ‚ąľ16¬įS by compiling seismic, magnetic, gravimetric and geochemical data along a 185 km-long crustal transect. We identified a crustal zonation which preserves the level of subduction input at the time of the crust's formation. Paired with the seafloor magnetization, the crustal zonation enabled us to qualitatively approximate the dynamic spreading history of the region. Further assessment of the recent tectonic activity and the degree of tectonic overprinting visible in the crust both suggest a complex tectonic history including a dynamically moving spreading center and the reorganizing of the local magma supply. Comparing the compiled data sets has revealed substantial differences in the opening mechanisms of the two arms of the Overlapping Spreading Center (OSC) that is made up by the northernmost tip of the Fonualei Rift and Spreading Center in the east and the southernmost segment of the Mangatolu Triple Junction in the west. The observed transition from a predominantly tectonic opening mechanism at the eastern OSC arm to a magmatic opening mechanism at the western OSC arm coincides with an equally sharp transition from and strongly subduction influenced crust to a crust with virtually no subduction input. The degree of subduction input alters the geochemical composition, as well as the lithospheric stress response. Key Points Oceanic crust in the north-eastern Lau Basin formed at the now reorganized FRSC-MTJ system The position and the opening mechanisms of back-arc basin spreading center's change more dynamically at mid-ocean ridges Different opening mechanisms at the southern Mangatolu Triple Junction and northern Fonualei Rift Spreading Center despite their proximit

    Basin inversion: reactivated rift structures in the central Ligurian Sea revealed using ocean bottom seismometers

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    The Alpine orogen and the Apennine system are part of the complex tectonic setting in the Mediterranean Sea caused by the convergence between Africa and Eurasia. Between 30 Ma and 15 Ma, the Apennines-Calabrian-Maghrebides subduction retreated in a southeast direction pulling Corsica and Sardinia away from the Eurasian landmass, opening the Ligurian Sea. In this extensional setting, the Ligurian Sea was formed as a back-arc basin. The northern margin of the Ligurian Basin shows notable seismicity at the Alpine front, including frequent magnitude 4 events. Seismicity decreases offshore towards the basin center and Corsica, revealing a diffuse distribution of low-magnitude earthquakes. Within the framework of the AlpArray research initiative, a long-term amphibious seismological experiment was conducted in the Ligurian Sea to investigate the lithospheric structure and the seismicity in the Ligurian Basin. The passive seismic network consisted of 29 broad-band ocean bottom stations from Germany and France next to permanent and temporary broad-band land stations. The ocean bottom stations were in operation between June 2017 and February 2018. Two clusters consisting of 18 earthquakes occurred between ‚ąľ‚ÄČ10 km to ‚ąľ‚ÄČ16 km depth below the sea surface, within the lower crust and uppermost mantle, in the centre of the basin. Thrust faulting focal mechanisms indicate compression and tectonic inversion of the Ligurian Basin, which is an abandoned Oligocene‚ÄďMiocene rift basin. The basin inversion is suggested to be related to the Africa‚ÄďEurope plate convergence. The locations and focal mechanisms of seismicity suggest reactivation of pre-existing rifting-related structures. Slightly different striking directions of presumed rifting-related faults in the basin center compared to faults further east and hence away from the rift basin may reflect the counter-clockwise rotation of the Corsica‚ÄďSardinia block. Mantle refractions Pn and Sn have apparent velocities of 8.2 km/s and 4.7 km/s. The low Vp-Vs-ratio of 1.72 indicates a more brittle behavior of the mantle material. This supports the hypothesis of strengthening of crust and uppermost mantle during the Oligocene‚ÄďMiocene rifting-related extension and thinning of continental crust. This project is part of the DFG Priority Program ‚ÄúMountain Building Processes in Four Dimensions (4DMB)‚ÄĚ. This research has been supported by the Deutsche Forschungsgemeinschaft (grant nos. TH_2440/1-1, KO_2961/6-1, and LA_2970/4-1) and the Agence Nationale de la Recherche (grant no. ANR-15-CE31- 0015)

    3D crustal structure of the Ligurian Basin revealed by surface wave tomography using ocean bottom seismometer data

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    The Liguro-Proven√ßal basin was formed as a back-arc basin of the retreating Calabrian‚ÄďApennines subduction zone during the Oligocene and Miocene. The resulting rotation of the Corsica‚ÄďSardinia block is associated with rifting, shaping the Ligurian Basin. It is still debated whether oceanic or atypical oceanic crust was formed or if the crust is continental and experienced extreme thinning during the opening of the basin. We perform ambient noise tomography, also taking into account teleseismic events, using an amphibious network of seismic stations, including 22 broadband ocean bottom seismometers (OBSs), to investigate the lithospheric structure of the Ligurian Basin. The instruments were installed in the Ligurian Basin for 8 months between June 2017 and February 2018 as part of the AlpArray seismic network. Because of additional noise sources in the ocean, OBS data are rarely used for ambient noise studies. However, we carefully pre-processed the data, including corrections for instrument tilt and seafloor compliance and excluding higher modes of the ambient-noise Rayleigh waves. We calculate daily cross-correlation functions for the AlpArray OBS array and surrounding land stations. We also correlate short time windows that include teleseismic earthquakes, allowing us to derive surface wave group velocities for longer periods than using ambient noise only. We obtain group velocity maps by inverting Green's functions derived from the cross-correlation of ambient noise and teleseismic events. We then used the resulting 3D group velocity information to calculate 1D depth inversions for S-wave velocities. The group velocity and shear-wave velocity results compare well to existing large-scale studies that partly include the study area. We observe a high-velocity area beneath the Argentera Massif in onshore France, roughly 10‚ÄČkm below sea level. We interpret this as the root of the Argentera Massif. Our results add spatial resolution to known seismic velocities in the Ligurian Basin, thereby augmenting existing seismic profiles. The velocity model indicates that the southwestern and north-eastern Ligurian Basin are structurally separate (Figure 1, panel a). In agreement with existing seismic studies, our shear-wave velocity maps indicate a deepening of the Moho from 12‚ÄČkm at the south-western basin centre to 20‚Äď25‚ÄČkm at the Ligurian coast in the north-east and over 30‚ÄČkm at the Proven√ßal coast. The lack of high crustal vp/vs ratios beneath the southwestern part of the Ligurian Basin precludes mantle serpentinisation there. The poster summarises the findings published in Solid Earth (Wolf et al. (2021)

    Seismic refraction and wide-angle reflection OBS data from profile P05 during SONNE cruise SO267 (ARCHIMEDES), Lau Basin

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    The dataset contains ocean bottom hydrophone (OBH) data acquired along profile P05 during RV Sonne Expedition SO267 (project ARCHIMEDES) to the Lau Basin, Southwestern Pacific in December 2018. This seismic refraction data set contains 34 OBS that all recorded the shots along the ~220 km long seismic transect successfully. Data for two different shot intervals (50m and 150m) were acquired shooting from east to west and from west to east respectively. An 84 l airgun array served as seismic source that was towed behind the vessel 8 m below sea surface. The data were processed using standard methods for relocation of the instrument at the seafloor, clock drift correction, deconvolution and filtering

    Ligurian Ocean Bottom Seismology and Tectonics Research (LOBSTER)

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    The LOBSTER project constitutes the offshore component of the DFG Priority Program ‚ÄúMountain Building Processes in Four Dimensions‚ÄĚ (SPP 2017, 4DMB) and aimed to expand the densely spaced AlpArray broadband seismic network to the offshore domain in the Ligurian Sea. The LOBSTER program encompassed research cruises on the French RV Pourquoi Pas? in 2017 to deploy a long-term ocean bottom seismology network that was recovered using the German RV Maria S. Merian in 2018 (Fig. 1). The LOBSTER long-term seismic network consisted of 7 French (from IPGP) and 22 German (from the DEPAS pool and from GEOMAR) stations. During the second cruise an active seismic experiment was conducted to complement the passive seismology study. The refraction seismic data acquisition was conducted along two wide-angle profiles: P01 runs from the Gulf of Lion to Corsica and P02 trends parallel to the center of the Ligurian Basin in a NE-SW direction. Both profiles were analyzed using a travel time tomography (Dannowski et al., 2020 and in prep). The combined data set in addition to high-resolution bathymetry data shed light on today‚Äôs active deformation of the Ligurian Sea (Thorwart et al., 2021). In addition, the 3-D crustal and upper mantle structure of the Ligurian Basin was inferred from surface wave tomography (Wolf et al., 2021). The main technical aim of the LOBSTER project is to provide consistent data that can be smoothly integrated with the onshore seismology data. Key features in the data pre-processing are the correct timing, determining of the orientation of the horizontal seismometer components, and the searchability and availability of the data based on FAIR data standards. LOBSTER studied the Ligurian Sea at the transition from the western Alpine orogen to the Apennine system. This complex geodynamic setting is manifested in pronounced variations in crustal thickness. Topographic gradients in the area are the largest for the entire Alpine-Mediterranean domain, rising from -2500 m in the Ligurian basin to > +3000 m in the Alpine-Apennine orogen over a distance of less than 100 km. The Ligurian Basin is a back-arc basin opened by the south-eastward trench retreat of the Apennines-Calabria-Maghrebides subduction zone, which also triggered the opening of the adjacent western Mediterranean basins. The recent deformation in the Ligurian Sea results from compression along its northern margin (0.3 - 1.5 mm/year shortening), but no significant convergence is evident from GPS data, and rates of deformation are very low. The LOBSTER data set offers a better understanding of the complex geodynamic setting of the Ligurian Sea, which is characterized by pronounced variations in crustal thickness. Based on the LOBSTER data the following conclusions were documented: - Extension in the Ligurian Basin led to stretched and very thin continental crust or exhumed, partially serpentinised mantle. - Continental crustal thinning from north to south is related to the increase of extension with increasing distance from the rotation pole of the anticlockwise rotation of the Corsica‚ÄďSardinia block. - Seafloor spreading and formation of mantle-derived oceanic crust was not initiated during the extension of the Ligurian Basin. - The Ligurian Sea is currently closing while Africa and Eurasia are converging. Part of the stresses are taken up in the basin center through re-activation of extension-related faults. Data analysis is still ongoing and further results are expected from local earthquake tomography in the area of the Alps-Ligurian Junction conducted with the data from the long-term ocean bottom seismometer deployment

    eFAIRs project: current status and next steps

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    The seismological community promotes since decades standardisation of formats and services as well as open data policies which are making easy data exchange an asset for this community. Thus, data is made perfectly Findable and Accessible as well as Interoperable and Reusable with enhancements expected for the latter two. The strict and technical domain specific standardisation may complicate the sharing of more exotic data within the domain itself as well as hinder interoperability throughout the earth science community. Within eFAIRs, leveraging on the know-how of the major OBS park operators and seismological data curators within the Helmholtz association, we aim at facilitating integration of special datasets from the ocean floor enhancing interoperability and reusability. To achieve this goal, in close collaboration with AWI and Geomar, supported by IPGP, the Seismological Archive of the GFZ has created special workflows for OBS data curation. In particular, with close interaction with AWI, new datasets have been archived defining a new workflow which is being translated into guidelines for the community. Domain specific software have been modified to allow OBS data inclusion with specific additional metadata. Among these metadata also persistent identifiers of the instruments in use have been included for the first time from the AWI sensor information system. Next steps are going to enlarge the portfolio of keywords and standard vocabularies in use to facilitate data discovery from scientists of different domains. Finally we plan to adopt the developed workflows for OBS data management

    Project LOBSTER: DEPAS and GEOMAR ocean-bottom seismometer operations in the Ligurian Sea in 2017-2018

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    The long-term network comprising ocean bottom broadband seismometers (OBS) forms an integral part of the European AlpArray initiative and the German DFG Priority Programme SPP ‚ÄöMountain Building in 4 Dimensions' MB 4D (http://www.spp-mountainbuilding.de/). The instruments are deployed with a mean distance of 25 nm (46km) to the neighboring station (28 nm (51 km) to neighboring three stations) west and north of the island of Corsica. The westernmost instruments are located near the Gulf of Lions and the northernmost instruments were installed off the Ligurian coast. The scientific aim of the LOBSTER project is manifold: (1) characterisation of the crust and upper mantle of the Ligurian Basin and the transition from the oceanic to the continental domain; (2) understanding the structures and kinematics of rifting during the opening of the Ligurian Sea; (3) imaging the prolongation of the Alpine front; and (4) studying the recent deformation in the Ligurian Basin and the surrounding coastal areas as imaged through local seismicity. Additionally, the AlpArray OBS network was important to complete the densely spaced AlpArray broadband seismic network. The technical aim of the LOBSTER project is to provide consistent data that can be smoothly integrated into the land data. Instruments have been deployed in June 2017 by RV Pourquois Pas and recovered after 8 months of recording in January 2018 by RV Maria S Merian (MSM71)
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