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  • 1
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    Unknown
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 91 (B12). pp. 12711-12721.
    Publication Date: 2020-07-23
    Description: Four major NE trending postglacial volcanic and tectonic fissure swarms (volcanic systems) occur on the Reykjanes Peninsula, and the westernmost three are the main subject of this paper. Two main types of basaltic volcanoes are associated with these systems: shields of picrite and olivine tholeiite and tholeiite fissures. The average volume of 26 shields is 1.11 km3, and the total production is 29 km3, whereas the corresponding figures for lavas from 101 volcanic fissures are 0.11 km3 and 11 km3. The tectonic fractures are either tension fractures or normal faults of widths up to 20 m, throws up to 10 m, and lengths up to several kilometers. The volcanism and tectonics can be explained by magmatic pressure changes in ellipsoidal magma reservoirs located beneath the fissure swarms. A magmatic pressure increase of the order of 10 MPa is found to be sufficient for an excess uplift of the order of several meters, which is all that is needed to account for the fractures and measured dilation in the fissure swarms. It is concluded that most shield volcanoes, in particular the picrite shields and the large olivine tholeiite shields, formed during the early postglacial period and that their formation was facilitated by the stress field generated as a result of rapid uplift and bending of the crust above the reservoirs. Since that time the reservoirs have become independent systems, the volcanism has been confined to fissures, and the production rate has decreased significantly. During typical fissure eruptions (0.015 km3), only the uppermost several hundred meters of the source reservoir, depending on its magma content, supply magma to the eruption.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2021-03-29
    Description: Piton de la Fournaise (Réunion Island) is an active basaltic shield volcano in the south-western part of the Indian Ocean. The activity consists essentially of lava being issued from two rift zones close to the summit cone. The summit cone has been monitored since 1980 by the OVPF (Volcanological Observatory of Piton de la Fournaise). Geodetic data and radar interferometry show a systematic asymmetric pattern of deformation associated with all the N–S trending eruptive fissures (Briole et al. 1998, Sigmundsson et al. 1999). The asymmetric deformation has been interpreted in various ways. The two main models proposed are (1) eastward dip of the dykes, based on inversion of data provided by radar interferometry (Sigmundsson et al 1999), and (2) the existence of a free boundary in the east part of the volcano. The second model allows the accommodation of dykes by eastward displacements, whilst the western part of the volcano is supported by the existing Piton des Neiges (Lénat et al., 1989). However,no displacements occur along the eastern coastline of Piton de la Fournaise. The only parts of the volcano affected by deformation are the rift zones and the summit cone. Moreover, geodetic data provided by the new real-time GPS network show that there is an asymmetric deformation of the summit cone prior to eruption (Staudacher 2005). The deformation itself seems to be related to pressure increase in the magma chamber. Absence of permanent displacements during periods of rest (such as 1992–1998) (Briole et al. 1998) support this link between magmatic pressure and deformation. Here we complement previous deformation studies by the results of several numerical models that aim at understanding the internal processes resulting in deformation of the volcano...
    Description: conference
    Keywords: 551 ; VAD 700 ; VAD 300 ; VAE 200 ; VEZ 200 ; Regionaler Vulkanismus {Geologie} ; Vulkanformen und Vulkantypen {Geologie} ; Geodynamik der Lithosphäre {Geologie} ; Indischer Ozean {Geologie} ; Piton de la Fournaise ; Schildvulkan ; Deformation 〈Geologie〉
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 3
    Publication Date: 2021-03-29
    Description: Dykes are magma-driven extension fractures and the main conduits for magma in volcanic eruptions. To understand the mechanics of dyke emplacement is thus essential to assess volcanic hazards. To improve the understanding of the processes of dyke initiation from shallow magma chambers and dyke propagation through a mechanicallylayered crust, field measurements and observations from Tenerife (Canary Islands) are used and compared with the results from numerical models. Careful studies of 550 dykes in three profiles in the Anaga massif (Tenerife) include measurements of dyke geometry and orientation. The results of these measurements show that dykes have been injected from a deep-seated reservoir during the shield-building phase. Furthermore, the dyke attitudes agree with the main axial trends of Tenerife that are preserved in the old massifs of Teno, Anaga, and Roque del Conde...
    Description: conference
    Keywords: 551 ; VAE 150 ; VEZ 130 ; Strukturelle Erscheinungen {Strukturgeologie} ; Inselgruppen {Atlantischer Ozean: Geologie} ; Teneriffa ; Gang 〈Geologie〉
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 4
    Publication Date: 2021-03-29
    Description: Der Holozäne Thingvellir Spaltenschwarm ist Teil des 60 km langen Hengill Vulkansystems, das sich in der Westvulkanischen Zone in Island befindet und ein etwa 9000 Jahre altes basaltisches Lavafeld nördlich des Sees Thingvallavatn durchquert. Dieser Spaltenschwarm enthält einige der größten postglazialen Verwerfungen und Brüche, die in der Riftzone Islands anzutreffen sind. Das Zentrum des Hengill Vulkansystems bildet der 0.8 Ma alte gleichnamige Vulkan. Der Gipfel des Vulkans ist durchzogen von NE-SW streichenden Abschiebungen, von denen einige bis zum See Thingvallavatn verfolgt werden können. Der Thingvellir Spaltenschwarm wird von nahezu vertikalen Zugbrüchen und geöffneten Abschiebungen dominiert...
    Description: conference
    Keywords: 551 ; VAE 830 ; VAE 150 ; VED 500 ; Bruchschollenstrukturen {Geologie} ; Strukturelle Erscheinungen {Strukturgeologie} ; Island {Geologie} ; Island ; Thingvellir ; Abschiebung 〉Geologie〉
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 5
    Publication Date: 2021-03-29
    Description: Oceanic transform faults and ridge segments form a network where mechanical interaction is to be expected. In particular, dike emplacement in ridge segments is likely to affect earthquake activity in the adjacent transform faults through processes such as stress transfer. Similarly, strike-slip displacement across transform faults may trigger dike injections and, eventually, eruptions in the adjacent ridge segments. For obvious reasons, direct observations of the possible mechanical interaction between submarine transform zones and ridge segments at mid-ocean ridges are difficult. The subaerial seismic zones of Iceland, however, are in clear spatial connections with the adjacent volcanic zones. These zones, therefore, provide excellent opportunities to study stress transfer between volcanic and seismic zones (Gudmundsson 2000)...
    Description: conference
    Keywords: 551 ; VAE 130 ; VAE 200 ; TOH 520 ; VAD 200 ; Geomechanik ; Geodynamik der Lithosphäre {Geologie} ; Mechanismen von Erdbeben und seismischen Störungen {Geophysik} ; Vulkanische Tätigkeit {Geologie} ; Island ; Horizontalverschiebung ; Vulkanismus ; Induzierte Seismizität
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 6
    facet.materialart.
    Unknown
    Universitätsverlag Göttingen
    Publication Date: 2021-03-29
    Description: Holocene shield volcanoes (lava shields) are common in Iceland, but they are restricted in space and time. As regards space, most of the shield volcanoes in Iceland occur within two bands in the West and North Volcanic Zones. There are no shields in the East Volcanic Zone apart from the island of Surtsey. The shields are mostly at the margins of or outside the volcanic systems. As regards time, many Holocene shield volcanoes formed some 5000–10000 years ago during early postglacial time. Apart from the shield on top of the island of Surtsey, there are no known shields in Iceland younger than about 3500B.P....
    Description: conference
    Keywords: 551 ; VAD 700 ; VAD 300 ; Regionaler Vulkanismus {Geologie} ; Vulkanformen und Vulkantypen {Geologie} ; Island ; Holozän ; Schildvulkan
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 7
    facet.materialart.
    Unknown
    Universitätsverlag Göttingen
    Publication Date: 2021-03-29
    Description: When viewed as ideal elastic cracks, seismogenic faults are often modeled as decreases from the host rock to the boundary between the core and the damage zone. mode II or mode III cracks in semiinfinite elastic bodies or half spaces. These models normally assume the rock to be homogeneous and isotropic. Such assumptions may be justified and necessary when using closed-form analytical solutions for fault displacement. They are not justified, however, when we attempt to understand fault-displacement profiles along earthquake rupture sites or in paleofault studies. This follows because crustal segments hosting faults are, as a rule, not homogeneous and isotropic, but rather heterogeneous and anisotropic. In particular, the fault rocks commonly form layers or units parallel with the fault plane. Also, the mechanical properties of the rocks next to the fault change as the fault develops (Gudmundsson 2004). During repeated earthquakes in a seismogenic fault zone, two main rock units develop around the fault plane. One unit is the core, located next to the fault plane and normally composed of soft (low Young’s modulus) breccia, gouge, and other cataclastic rocks. The other unit is the damage zone, containing some cataclastic rocks but characterized by fractures of various types...
    Description: conference
    Keywords: 551 ; VAE 140 ; VAE 150 ; Gesteinsdeformation {Strukturgeologie} ; Strukturelle Erscheinungen {Strukturgeologie} ; Bruchzone ; Deformation 〈Geologie〉 ; Verwerfung ; Modellierung
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 8
    Publication Date: 2021-03-29
    Description: Der Geitafell-Vulkan ist ein erloschener tertiärer Zentralvulkan (Stratovulkan) in Südost-Island. Aufgrund tiefer glazialer Erosion ist das Innere des Vulkans bis hinab zur erloschenen krustalen Magmakammer aufgeschlossen. Das bietet die einmalige Möglichkeit, die Infrastruktur und die tektonische Entwicklung eines typischen isländischen Zentralvulkans zu untersuchen. Der Geitafell-Vulkan besteht aus einer Abfolge von eruptiven Materialien unterschiedlicher mechanischer Eigenschaften wie zum Beispiel basaltische Laven, Hyaloklastite und saure Extrusiva. Im Kern des Vulkans ist der obere Teil einer erloschenen krustalen Magmakammer in Form mehrerer Gabbrokörper aufgeschlossen. Im direkten Kontakt mit der Magmakammer befindet sich ein sehr dichter Schwarm von Kegelgängen, die von der Magmakammer injiziert wurden, als der Geitafell-Vulkan von etwa 5 bis 6Ma aktiv war (Fridleifsson, 1983). Um unser Verständnis über die vulkanotektonische Entwicklung des Zentralvulkans zu verbessern, wurden im Geitafell-Gebiet mehr als 500 Gänge und Kegelgänge, 400 Mineralgänge und etwa 1100 Klüfte gemessen...
    Description: conference
    Keywords: 551 ; VAD 300 ; VAD 700 ; VEZ 130 ; Vulkanformen und Vulkantypen {Geologie} ; Regionaler Vulkanismus {Geologie} ; Inselgruppen {Atlantischer Ozean: Geologie} ; Island ; Stratovulkan
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 9
    Publication Date: 2021-03-29
    Description: Zur Nutzung von Erdwärme aus Teufen zwischen 2–5 km werden häufig Systeme aus einer Injektions- und Förderbohrung (‚Dubletten-System‘) genutzt. Dabei wird durch die Injektionsbohrung ein Fluid in den Untergrund verpresst, welches sich erhitzt und durch die Förderbohrung wieder an die Oberfläche gelangt. Ein wesentlicher Parameter für die produktive Nutzung von solchen Dubletten-Systemen ist eine hohe Permeabilität der Gesteine im Untergrund. Häufig werden in solchen geothermischen Reservoiren die Wegsamkeiten für Fluide von Brüchen kontrolliert, die bereits vorhanden sind oder künstlich erzeugt werden müssen (hydraulische Stimulation). Deshalb ist die Kenntnis über existierende Bruchgeometrien sowie Vernetzung der Bruchsysteme von fundamentaler Notwendigkeit zur Abschätzung der Permeabilität von geothermischen Reservoiren. Seismische Verfahren und Bohrkernanalysen besitzen im Allgemeinen dafür eine zu geringe Auflösung. Daher bieten sich dreidimensionale Rekonstruktionen des Bruchsystems aus analogen Obertageaufschlüssen an (vgl. Philipp et al. 2005; 2006)...
    Description: conference
    Keywords: 551 ; VDH 110 ; VAE 150 ; TOO 000 ; VRG 000 ; Untere Trias ; Strukturelle Erscheinungen {Strukturgeologie} ; Geothermik {Geophysik} ; Geothermalfelder ; Karlshafen 〈Region〉 ; Reinhausen 〈Gleichen, Göttingen, Region〉 ; Mittlerer Buntsandstein ; Strukturgeologie ; Permeabiblität ; Geothermische Energie
    Language: German
    Type: anthologyArticle , publishedVersion
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  • 10
    Publication Date: 2021-03-29
    Description: Das Holozäne Hengill-Vulkansystem liegt in der aktiven Westvulkanischen Zone in Südwestisland. Es beinhaltet den Hengill-Zentralvulkan, der sich südlich des Sees Thingvallavatn befindet, und ist eines der aktivsten geothermischen Systeme Islands (Abb. 1). Die aktuelle Spreizungsrate in der Westvulkanischen Zone liegt zwischen 3 und 7mma−1 bei einer Subsidenzrate von 1mma−1 (Tryggvason 1982; La Femina et al. 2005). Das Hengill-Vulkansystem ist 60–70km lang und zwischen 5 und 10km breit. Strukturgeologisch wird das Gebiet von großen NNE-streichenden Abschiebungen dominiert. Das Hauptziel dieser Untersuchung ist, das Verständnis für die Bruchentwicklung und die Fluidtransportmechanismen im Hengill-Gebiet zu verbessern. Dieses Verständnis ist notwendig, um realistischere Modelle über den Fluidtransport in den geothermischen Feldern erstellen zu können und um bessere Prognosen über ihre Lebensdauer zu ermöglichen. Weiterhin soll der Kenntnisstand über den Einfluss von Wässern auf Erdbebenentstehung untersucht werden, da in diesem Gebiet die meisten Erdbeben durch Fluidüberdruck ausgelöst werden.
    Description: conference
    Keywords: 551 ; VED 500 ; VAD 700 ; VAE 150 ; VAE 140 ; TOO 000 ; Island {Geologie} ; Regionaler Vulkanismus {Geologie} ; Strukturelle Erscheinungen {Strukturgeologie} ; Gesteinsdeformation {Strukturgeologie} ; Geothermik {Geophysik} ; Island 〈Südwest〉 ; Vulkan ; Klüftung ; Störung 〈Geologie〉 ; Wasserdurchlässigkeit ; Geothermische Energie
    Language: German
    Type: anthologyArticle , publishedVersion
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