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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Central Andes are the Earth's highest mountain belt formed by ocean–continent collision. Most of this uplift is thought to have occurred in the past 20 Myr, owing mainly to thickening of the continental crust, dominated by tectonic shortening. Here we use P-to-S ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Gefässchirurgie 2 (1997), S. 22-26 
    ISSN: 1434-3932
    Keywords: Schlüsselwörter Armvenen ; Infrainguinale Rekonstruktion ; Angioskopie ; Key words Upper extremity veins ; Infrainguinale bypass ; Angioscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The autogenous greater saphenous vein is the material of choice for infrainguinal arterial reconstructions. Substantial problems arise when this conduit is of poor quality or is absent because of earlier use. An alternative source for autogenous vein material are the upper extremities. In a retrospective study we compare 31 reconstructions with arm veins to 72 greater saphenous vein bypasses. In both groups quality control and valvulotomy were accomplished by using an angioscope. The two groups were similar concerning patient characteristic and results. The primary assisted patency rate in the arm vein group (93%, 36 months) did not differ significantly from the patency in the saphenous vein group (84%, 36 months, p=0.42). Similar results were seen for limb salvage. In conclusion, arm veins can be used as an adequate alternative to the greater saphenous vein in infrainguinal arterial reconstructions. Intraoperative quality control and postoperative follow-up are the keys achieving good long-term results.
    Notes: Zusammenfassung Die autologe V. saphena magna steht für infrainguinale arterielle Revaskularisation nicht immer in ausreichender Länge zur Verfügung, da sie für vorangegangene Revaskularisationen bereits verbraucht wurde oder eine ungenügende Qualität aufweist. Zur Beantwortung der Frage, ob mit autologem Armvenenmatrial ähnliche Resultate wie mit Saphena magna erreicht werden können, verglichen wir retrospektiv 31 Armvenenrekonstruktionen mit 72 autologen Saphena-magna-Brücken. Sämtliche Venen wurden unter angioskopischer Sicht einer Qualitätskontrolle unterzogen und gleichzeitig valvulotomiert. Die beiden Gruppen unterschieden sich bezüglich Krankengut und Resultate nicht signifikant voneinander. Die primär assistierte Offenrate mit Armvenen lag bei 93% nach 3 Jahren, mit frei verlegter Saphena magna bei 84% nach der gleichen Zeit (p=0,42). Mit Armvenen können in der peripheren Bypasschirurgie ähnliche Resultate erreicht werden wie mit der V. saphena magna. Entscheidende Bedeutung kommt dabei der Qualitätskontrolle des Transplantats intraoperativ sowie der lückenlosen postoperativen Überwachung zu.
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  • 3
    Publication Date: 2017-02-14
    Description: The southern central Chilean margin at the site of the largest historically recorded earthquake in the Valdivia region, in 1960 (Mw = 9.5), is part of the 5000-km-long active subduction system whose geodynamic evolution is controversially debated and poorly understood. Covering the area between 36° and 40°S, the oceanic crust is segmented by prominent fracture zones. The offshore forearc and its onshore continuation show a complex image with segments of varying geophysical character, and several fault systems active during the past 24 m.y. In autumn 2001, the project SPOC was organized to study the Subduction Processes Off Chile, with a focus on the seismogenic coupling zone and the forearc. The acquired seismic data crossing the Chilean subduction system were gathered in a combined offshore-onshore survey and provide new insights into the lithospheric structure and evolution of active margins with insignificant frontal accretion.
    Type: Article , NonPeerReviewed
    Format: text
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  • 4
    Publication Date: 2014-05-20
    Description: We obtained high-precision locations for 5250 earthquakes in the Iquique segment of the northern Chilean subduction zone from two temporary local seismic networks around 21°S. A double seismic zone in the downgoing Nazca slab can be clearly identified. One band of seismicity is located at the plate interface and a second one 20–25 km deeper in the oceanic mantle. It can be traced updip to uncommonly shallow levels of 50 km. A combined interpretation of seismicity and reflectivity along the seismic ANCORP’96 experiment suggests the prevalence of fluid processes in the subducted oceanic crust as well as in the uppermost 20 km of the mantle. Crustal seismicity is pervasive below the Coastal Cordillera. Beneath the Precordillera, the lower bound of crustal seismicity delineates a sharp west-dipping boundary down to 20 km depth, consistent with earlier findings indicating a rheological boundary.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 5
    Publication Date: 2016-01-08
    Description: The coda of passive seismic recordings is often rich in arrivals that are coherent across several stations. If reflections can be extracted, then they may be used for seismic reflection subsurface imaging. With the objective to image the upper crust of the North Chilean Precordillera (Central Andes; approximate location 21°S 69°W), we developed a workflow to process passive seismic data into subsurface reflection images. We analysed the waveform recordings of several hundred microseismic events using signal processing and imaging techniques adapted from active (controlled source) seismic imaging as used in the oil industry. Key processing steps involved precise arrival time picking and hypocentre determination, removing signal amplitude variations due to varying source radiation patterns, identification and separation of reflections from coherent noise, and transformation of the processed waveforms into images of the subsurface reflectivity. When designing our microseismic reflection imaging workflow, we took advantage of the fact that the passive seismic recording geometry with the hypocentres located at depth and the receivers positioned at the surface resembles a reverse vertical-seismic profiling experiment. The resultant P - and S -wave reflection images reveal several reflective features, such as an approximate 15° westward dipping reflector over the 5–25 km depth range that largely coincides with a distinct seismicity boundary. We interpret the imaged interface as the brittle-ductile transition zone boundary, possibly enhanced by a tectonic shear zone. For the area of the North Chilean Precordillera, the deduced microseismic reflection sections with horizontal extensions of about 50 km represent the first high-resolution images of the shallow crust, which could not be obtained from previous active-source seismic-reflection data.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 6
    Publication Date: 2020-02-12
    Description: In this study, we present an interpretation of seismic refraction profiles from the PISCO 94 experiment in northern Chile. As the PISCO experiment was a combined active and passive seismological study, we also discuss results of the passive part in the context of the seismic refraction model. Previous seismic refraction and gravimetric studies indicate a maximum crustal thickness of about 70 km beneath the Pre- and Western Cordillera. The new seismic refraction data lead to a differentiated image of the Andean crust which shows strong varying characteristics. The crustal discontinuities (up to five are detected) dip from W to E. The upper crust has a thickness of 18 km (Precordillera) to 23 km (magmatic arc) underlain by the recent middle crust down to 35-45 km where the velocity increases to about 7 km/s at its base. This crustal level is interpreted as old continental lower crust and its base as blurred continental (paleo) Moho. Beneath the Precordillera, a strong discontinuity at 70 km depth with a velocity increase to about 8 km/s was detected, interpreted as the recent geophysical Moho. For the magmatic arc, this deep discontinuity could not be found by active seismic measurements. The tomographic models of the seismological studies, in general, confirm the seismic refraction results. Anomalously high vp/vs rations in the deeper part of the forearc indicate a hydrated mantle wedge consisting of serpentine and amphibole-bearing peridotite and the 70 km discontinuity is interpreted as the boundary between these two different stages of the hydrated mantle wedge. A zone of high attenuation (Qp) and high vp/vs ratios beneath the magmatic arc coincides with the low velocity zones and indicates partially molten rocks from a depth of 20 km down to the asthenospheric wedge.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 7
    Publication Date: 2020-02-12
    Description: A temporary seismological network, which was located in the Antofagasta (northern Chile) region, recorded a large part of the aftershocks from a MW = 8.0 earthquake in 1995. Results from a tomographic inversion show that the aftershocks were concentrated in a plane, approximately 3 km thick spatial zone. Comparison of our results with earlier processed wide-angle reflection data, shows clearly that this zone is positioned at the top of the oceanic crust. Therefore, it represents the shearing boundary between the subducting oceanic and the continental plate, and gives an in-situ estimation of the thickness of the boundary. Outside of this zone, events were detected in the continental crust, as well as within the oceanic mantle.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 8
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    In:  64. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (Berlin 2004)
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 9
  • 10
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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