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Izvestiya, Atmospheric and Oceanic Physics - Tsunami forecast possibilities for areas with a small base of historical tsunamis have been discussed using the Probabilistic Tsunami Hazard Assessment...  相似文献   
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Our analysis of new bathymetric data reveals six submarine landslides at the eastern Sunda margin between central Java and Sumba Island, Indonesia. Their volumes range between 1 km3 in the Java fore-arc basin up to 20 km3 at the trench off Sumba and Sumbawa. We estimate the potential hazard of each event by modeling the corresponding tsunami and its run-up on nearby coasts. Four slides are situated remarkably close to the epicenter of the 1977 tsunamigenic Sumba M w  = 8.3 earthquake. However, comparison of documented tsunami run-up heights and arrival times with our modeling results neither allows us to confirm nor can we falsify the hypothesis that the earthquake triggered these submarine landslides.  相似文献   
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Submarine landslides can generate local tsunamis with high run-ups, posing a hazard to human lives and coastal facilities. Both ancient (giant Storegga slide off Norwegian coast, 8200 B. P.) and recent (Papua New Guinea, 1998) events show high potential danger of tsunamigenic landslides and the importance of mitigation efforts. This contribution presents newly discovered landslides 70 km off Padang (Western Sumatra, Indonesia) based on recent bathymetry measurements. This highly populated city with over 750,000 inhabitants exhibits high tsunami vulnerability due to its very low elevation. We model tsunamis that might have been induced by the detected landslide events. Estimations of run-up heights extrapolated from offshore tsunami amplitudes for Padang and other locations in the northern Mentawai fore-arc basin yield maximum values of about 3 m. We also provide a systematic parametric study of landslide-induced tsunamis, which allows us to distinguish potentially dangerous scenarios for Padang. Inside the fore-arc basin, scenarios involving volumes of 0.5–25 km³ could endanger Padang. Apart from slide volume, the hazard distribution mainly depends on three landslide parameters: distance to Padang, water depth in the generation region, and slide direction.  相似文献   
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We use the technique of direct minimization of the Gibbs free energy of the 8-component (K2O-Na2O-Fe2O3-FeO-CaO-MgO-Al2O3-SiO2) multiphase system in order to determine the equilibrium mineral assemblages of rocks of different bulk chemical compositions equilibrated at various P-T conditions. The calculated modal compositions of rocks and experimental data on elastic moduli of single crystals are then used to calculate densities and isotropic elastic wave velocities of rocks together with their pressure and temperature derivatives. Sufficient accuracy of the calculations is confirmed by comparison with experimental data on the gabbro-eclogite transformation and precise ultrasonic measurements of elastic wave velocities in a number of magmatic and metamorphic rocks.We present calculated phase diagrams with isolines of density, elastic wave velocities, and their pressure and temperature derivatives for several anhydrous magmatic rocks, from granite to lherzolite. Density and elastic properties of rocks are controlled by their chemical compositions, especially the SiO2 content, and by P-T of equilibration, and they increase with pressure due to mineral reactions changing mineral assemblages from plagioclase-bearing and garnet-free to garnetbearing and plagioclase-free. TheV p -density correlation is high, and shows two clear trends: one for iron-poor ultramafic rocks and another for all the other rocks considered. Mineral reactions, which occur at high pressures, changeV p and density of anhydrous magmatic rocks following the well-known Birch (or a similar) law.Felsic, intermediate and mafic rocks can be well distinguished in theV p -V p /V s - diagram, although their values ofV p can be close to one another. TheV p -V p /V s -density diagrams together with calculated phase diagrams can serve as efficient instruments for petrologic interpretation of seismic velocities.  相似文献   
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In-situ elastic properties in deep boreholes are controlled by several factors, mainly by lithology, petrofabric, fluid-filled cracks and pores. In order to separate the effects of different factors it is useful to extract lithology-controlled part from observedin-situ velocities. For that purpose we calculated mineralogical composition and isotropic crack-free elastic properties in the lower part of the Kola borehole from bulk chemical compositions of core samples. We use a new technique of petrophysical modeling based on thermodynamic approach. The reasonable accuracy of the modeling is confirmed by comparison with the observations of mineralogical composition and laboratory measurements of density and elastic wave velocities in upper crustal crystalline rocks at high confining pressure. Calculations were carried out for 896 core samples from the depth segment of 6840–10535m. Using these results we estimate density and crack-free isotropic elastic properties of 554 lithology-defined layers composing this depth segment. Average synthetic P- wave velocity appears to be 2.7% higher than the velocity from Vertical Seismic Profiling (VSP), and 5% higher than sonic log velocity. Average synthetic S-wave velocity is 1.4 % higher than that from VSP. These differences can be explained by superposition of effects of fabric-related anisotropy, cracks aligned parallel to the foliation plain, and randomly oriented cracks, with the effect of cracks being the predominant control. Low sonic log velocities are likely caused by drilling-induced cracking (hydrofractures) in the borehole walls. The calculated synthetic density and velocity cross-sections can be used for much more detailed interpretations, for which, however, new, more detailed and reliable seismic data are required.  相似文献   
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