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The tsunamigenic earthquake (Mw?=?8.1) that occurred on 29 September 2009 at 17:48 UTC offshore of the Samoa archipelago east of the Tonga trench represents an example of the so-called ??outer-rise?? earthquakes. The areas most affected were the south coasts of Western and American Samoa, where almost 200 people were killed and run-up heights were measured in excess of 5?m at several locations along the coast. Moreover, tide gauge records showed a maximum peak-to-peak height of about 3.5?m near Pago Pago (American Samoa) and of 1.5?m offshore of Apia (Western Samoa). In this work, different fault models based on the focal mechanism solutions proposed by Global CMT and by USGS immediately after the 2009 Samoan earthquake are tested by comparing the near-field recorded signals (three offshore DART buoys and two coastal tide gauges) and the synthetic signals provided by the numerical simulations. The analysis points out that there are lights and shadows, in the sense that none of the computed tsunamis agrees satisfactorily with all the considered signals, although some of them reproduce some of the records quite well. This ??partial agreement?? and ??partial disagreement?? are analysed in the perspective of tsunami forecast and of Tsunami Early Warning System strategy.  相似文献   
2.
Argnani  A.  Tinti  S.  Zaniboni  F.  Pagnoni  G.  Armigliato  A.  Panetta  D.  Tonini  R. 《Marine Geophysical Researches》2011,32(1-2):299-311
Marine Geophysical Research - The southern Adriatic basin is the current foredeep of the Albanide fold-and-thrust belt that runs along the eastern boundary of the Adriatic basin and partly owes its...  相似文献   
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Summary The most important italian contributions on the regulation effect of a lake are outlined and hemphasized.  相似文献   
4.
In the current ΛCDM cosmological scenario, N -body simulations provide us with a universal mass profile, and consequently a universal equilibrium circular velocity of the virialized objects, as galaxies. In this paper we obtain, by combining kinematical data of their inner regions with global observational properties, the universal rotation curve of disc galaxies and the corresponding mass distribution out to their virial radius. This curve extends the results of Paper I, concerning the inner luminous regions of Sb–Im spirals, out to the edge of the galaxy haloes.  相似文献   
5.
Long-term multi-hazard assessment for El Misti volcano (Peru)   总被引:1,自引:1,他引:0  
We propose a long-term probabilistic multi-hazard assessment for El Misti Volcano, a composite cone located <20 km from Arequipa. The second largest Peruvian city is a rapidly expanding economic centre and is classified by UNESCO as World Heritage. We apply the Bayesian Event Tree code for Volcanic Hazard (BET_VH) to produce probabilistic hazard maps for the predominant volcanic phenomena that may affect c.900,000 people living around the volcano. The methodology accounts for the natural variability displayed by volcanoes in their eruptive behaviour, such as different types/sizes of eruptions and possible vent locations. For this purpose, we treat probabilistically several model runs for some of the main hazardous phenomena (lahars, pyroclastic density currents (PDCs), tephra fall and ballistic ejecta) and data from past eruptions at El Misti (tephra fall, PDCs and lahars) and at other volcanoes (PDCs). The hazard maps, although neglecting possible interactions among phenomena or cascade effects, have been produced with a homogeneous method and refer to a common time window of 1 year. The probability maps reveal that only the north and east suburbs of Arequipa are exposed to all volcanic threats except for ballistic ejecta, which are limited to the uninhabited but touristic summit cone. The probability for pyroclastic density currents reaching recently expanding urban areas and the city along ravines is around 0.05 %/year, similar to the probability obtained for roof-critical tephra loading during the rainy season. Lahars represent by far the most probable threat (around 10 %/year) because at least four radial drainage channels can convey them approximately 20 km away from the volcano across the entire city area in heavy rain episodes, even without eruption. The Río Chili Valley represents the major concern to city safety owing to the probable cascading effect of combined threats: PDCs and rockslides, dammed lake break-outs and subsequent lahars or floods. Although this study does not intend to replace the current El Misti hazard map, the quantitative results of this probabilistic multi-hazard assessment can be incorporated into a multi-risk analysis, to support decision makers in any future improvement of the current hazard evaluation, such as further land-use planning and possible emergency management.  相似文献   
6.
The influence of gravitational slope deformation (GSD) on erosion rates and the shape of mountain belts has been identified worldwide, particularly in valleys affected by glacial retreat. However, due to a lack of understanding about the main predisposing factors influencing their spatial distribution, size and failure mechanisms, the effective impact of GSD on the evolution of the landscape remains difficult to quantify. This study presents the first detailed, regional-scale GSD inventory of the entire Upper Rhone catchment (western Switzerland). The detection and mapping of GSD are performed by combining different remote sensing approaches. Moreover, we propose a detailed characterisation of GSD, taking into account geometry, morphology and failure mechanisms. Based on these analyses, more than 300 GSD are identified, corresponding to 11 % of the entire study area. Spatial and statistical analyses indicate that GSD are not uniformly distributed across the study area: six GSD clusters are highlighted, containing more than 80 % of the GSD events detected. Our observations suggest that the distribution of GSDs is primarily related to coexisting active tectonic processes (including high uplift gradients and earthquake activity) and pre-existing regional-scale, tectonic weakness zones. The region’s lithological and structural conditions, on the other hand, appear largely to influence the failure mechanisms and the sizes of the GSD detected.  相似文献   
7.
The M w = 9.1 mega-thrust Sumatra–Andaman earthquake that occurred on December 26, 2004, was followed by a devastating tsunami that killed hundreds of thousands of people and caused catastrophic effects on human settlements and environments along many coasts of the Indian Ocean, where even countries very far from the source were affected. One of these cases is represented by the Republic of Seychelles, where the tsunami reached the region about 7 h after the earthquake and produced relevant damages, despite the country was more than 4,500 km far from the seismic source. In the present work, we present and discuss a study of the 2004 Sumatra tsunami by means of numerical simulations with the attention focused on the effects observed at the Seychelles Archipelago, a region never previously investigated with this approach. The case is interesting since these islands lay on a very shallow oceanic platform with steep slopes so as the ocean depth changes from thousands to few tens of meters over short distances, with significant effects on the tsunami propagation features: the waves are strongly refracted by the oceanic platform and the tsunami signal is modified by the introduction of additional frequencies. The study is used also to validate the UBO-TSUFD numerical code on a real tsunami event in the far field, and the results are compared with the available observations, i.e., the sea level time series recorded at the Pointe La Rue station, Mahé Island, and run-up measurements and inundation lines surveyed few weeks after the tsunami at Praslin Island, where the tsunami hit during low tide. Synthetic results are found in good agreement with observations, even though some of the observations remain not fully solved. Moreover, simulations have been run in high-tide condition since the 2004 Sumatra tsunami hitting at high tide can be taken as the worst-case scenario for the Seychelles islands and used for tsunami hazard and risk assessments.  相似文献   
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