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V. Araa A. Felpeto M. Astiz A. García R. Ortiz R. Abella 《Journal of Volcanology and Geothermal Research》2000,103(1-4)
The island of Tenerife is volcanically complex, and its eruptive history predominantly reflects the processes and products of two different eruptive styles: (1) non-explosive effusions of basaltic lavas from fissure vents mostly aligned along two ridges; and (2) less frequent but explosive salic eruptions from central vents associated with the Las Cañadas volcanic edifice and associated summit caldera. We have taken into account this fundamental distinction to develop a volcanic-hazards zonation (for lava flows and ash fall only) that includes: definition of the principal hazards; identification of the areas that have higher probability of containing emission centres; and numerical modelling of the vulnerable areas to be affected by volcanic hazards. Not only does the volcanic-hazards zonation map provide emergency-management officials with an updated assessment of the volcanic hazards, but it also represents a starting point for the preparation of a volcanic risk map for Tenerife. Finally, the hazards-zonation map also furnishes the basis for the design of a proposed volcano surveillance network. 相似文献
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The application of a magnetotelluric surveying method, developed specifically for detection of strong conductivity contrasts, has permitted interpretations of the deep structure of two important volcanic formations in the Canary Archipelago: the Timanfaya (Lanzarote) and Teide (Tenerife) volcanoes. Beneath the Timanfaya volcano, a highly conductive body (p ≤ 1 Ω m) has been detected, which is interpreted as a shallow magma chamber associated with the eruption which took place between the years 1730 and 1736. The core of this intrusion, still largely molten, would be located at approximately 4 km depth and would still maintain temperatures in excess of 900 °C.In the Telde caldera the asymmetry of the apparent resistivity components indicates a double depression; furthermore, a highly conductive level encountered in the centre of the eastern part of the volcanic complex has been attributed to the persistance of relatively high temperatures in the root of the last salic dome, extruded inside the caldera. In both zones, the deep limiting horizon is a highly conductive layer corresponding to the mantle (15 km in Lanzarote and 13 km in Tenerife), whereas other, more superficial, discontinuities have been related to local structures. 相似文献
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Design of hysteretic dampers with optimal ductility for the transverse seismic control of cable‐stayed bridges 
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下载免费PDF全文 Alfredo Camara Roberto Cristantielli Miguel A. Astiz Christian Málaga‐Chuquitaype 《地震工程与结构动力学》2017,46(11):1811-1833
Cable‐stayed bridges require a careful consideration of the lateral force exerted by the deck on the towers under strong earthquakes. This work explores the seismic response of cable‐stayed bridges with yielding metallic dampers composed of triangular plates that connect the deck with the supports in the transverse direction. A design method based on an equivalent single‐degree of freedom approximation is proposed. This is proved valid for conventional cable‐stayed bridges with 200‐ and 400‐m main spans, but not 600 m. The height of the plates is chosen to (1) achieve a yielding capacity that limits the maximum force transmitted from the deck to the towers, and to (2) control the hysteretic energy that the dampers dissipate by defining their design ductility. In order to select the optimal ductility and the damper configuration, a multi‐objective response factor that accounts for the energy dissipation, peak damper displacement and low‐cycle fatigue is introduced. The design method is applied to cable‐stayed bridges with different spans and deck–support connections. The results show that the dissipation by plastic deformation in the dampers prevents significant damage in the towers of the short‐to‐medium‐span bridges under the extreme seismic actions. However, the transverse response of the towers in the bridge with a 600‐m main span is less sensitive to the dampers. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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This paper presents an evaluation of the lava flowhazard on Lanzarote (Canary Islands) by means of aprobabilistic maximum slope model. This model assumesthat the topography plays the major role indetermining the path that a lava flow will follow. Thearea selected for containing future emission centreshas been chosen taking into account thecharacteristics of the recent eruptive activity andthe present activity of the island. The results of thesimulations constitute hazard maps whose values ateach point represent the probability of being coveredby lava. These results are qualitatively analysed toprovide some indication of the risk to the lifelines(electricity, drinking water etc.) of the island. 相似文献
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A magnetotelluric survey was carried out in order to contribute to the definition of the deep structure of the Phlegraean Fields area affected by the bradyseismic crisis begun in the summer 1982. In a preliminary campaign carried out in autumn 1983, the MT measurements were made in eight sites, located between 0.3 and 5 km from the Harbour of Pozzuoli and affected by different degrees of uplift.In a second campaign (autumn, 1984) seven of the first eight MT soundings were repeated and four new sites were investigated, one of which located in a stable zone 10 km away from Pozzuoli.MT measurements show the presence of a thick conductive layer (<1 m) thinned underneath the town of Pozzuoli, where its top reaches the minimum depth (1.2–2 km). The upper horizon of this layer has a greater concavity than that produced by surface deformation. Below the conductive layer, the substratum became progressively more resistive with depth. This resistive basement is well defined in the soundings located far away from Pozzuoli. Here, on the contrary, a zone or body much more conductive than its surroundings is detected. This conductive body could correspond to a high temperature magmatic intrusion, probably already solidified, with a rough cylindrical shape with a base diameter of 1.5±0.5 km.Introducing into the obtained model the depth of the conductive horizon desumed from the deep geothermal wells, the top of the intrusive body would lye at 3–4 km depth.A small uplift of this body related to tectonic readjustments eventually induced by strong earthquakes recently occurred in near zones could explain the surface deformation observed during the present bradyseismic crisis. 相似文献
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