Implementation of effective seismic input for soil-structure interaction systems     

Marco G. Cremonini  Paul Christiano  Jacobo Bielak 《地震工程与结构动力学》1988,16(4):615-625

A previously introduced method for transmitting effective seismic excitation to a discretized soil-structure system implemented. The method permits free-field excitation of a linear soil system to be specified within the regie of computation, arbitrarily close to a zone that includes the (possibly non-linear) structure and local subgrade and bae, thus eliminating the need to transmit the seismic excitation through artificial boundaries. This approach is demonse through a numerical example comprising a linear, two-dimensional system. Some comments also are made on the rere efficiencies of various local absorbing boundaries.  相似文献   

Benthic Fluxes of Dissolved Inorganic Nitrogen in a Coastal Lagoon of the Northern Adriatic Sea: an Interpretation of Spatial Variability Based on Sediment Features and Infauna Activity   总被引：1，自引：0，他引：1  

Daniele Nizzoli  Giuseppe Castaldelli  Marco Bartoli  David Thomas Welsh  Patricia Arriaga Gomez  Anna Elisa Fano  Pierluigi Viaroli 《Marine Ecology》2002,23(S1):297-306

Abstract. Dark respiration rates, dissolved inorganic nitrogen (DIN) fluxes and nitrification rates were measured at two sites in the microtidal Sacca di Goro lagoon in September 2000. DIN fluxes correlated with the biomass of the dominant macrofauna species (the amphipod Corophium spp. at station Giralda and the polychaete Neanthes spp. at station Faro). Respiration (> 6 mmol O₂ m⁻²h⁻¹) and ammonium fluxes (> 80μmol N m⁻²h⁻¹) were higher at station Giralda despite the lower organic matter content (4.5 %) and lower macrofauna biomass (4 g AFDW m⁻²). At both sites ammonium fluxes were significantly correlated with the biomass of the benthic infauna, but Corophium stimulated ammonium NH₄⁺ fluxes 3-fold compared to Neanthes. The amphipod also enhanced nitrification rates (> 300 μmol N m⁻²h⁻¹) due to the high density of its burrows, the higher NH₄⁺ regeneration rates and the enhanced oxygen supply to the bacteria.  相似文献   

Transtensional shear zones controlling volcanic eruptions: the Middle Pleistocene Mt Amiata volcano (inner Northern Apennines,Italy)     

Andrea Brogi  Domenico Liotta  Marco Meccheri  Lorenzo Fabbrini 《地学学报》2010,22(2):137-146

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Geochemistry of trace elements in surface waters of the Arno River Basin,northern Tuscany,Italy     

Gianni Cortecci  Tiziano Boschetti  Enrico Dinelli  Rosa Cidu  Francesca Podda  Marco Doveri 《Applied Geochemistry》2009

Trace element geochemistry of the Arno River and its main tributaries was investigated on the basis of two sampling campaigns carried out in November 1996 and June 1997. By analyzing filtered and unfiltered water samples, Fe and Al are found in solution mainly as colloidal particles of size lower than 0.45 μm. In June (lower flow rate), Fe and Al are enriched in the filtered waters from the main river, and this feature was interpreted in terms of higher water temperature promoting the formation of smaller particles, thus reducing their aggregation properties. Iron and Al show perfectly synchronous downstream profiles along the Arno River, correlate quite well each to other, and display abrupt concentration increases near to Florence, where the lithology of the catchment changes from siliciclastic dominated to clay-sand (lacustrine-marine)-dominated. The same behaviour is shown by most of the other trace elements in the river, thus supporting a general lithological control. Trace elements in the final part of the Arno River are influenced by flocculation processes in addition to mixing. Adsorption phenomena on oxy-hydroxides are denoted by good elemental correlations with Fe (and Al). Sporadic anomalous concentration values, possibly related to anthropogenic contributions, may prevent such correlations. Referring to the quality of waters for potable use and fish life, toxic elements are below the acceptable limits of current European regulations, with few exceptions for Hg exceeding guideline values. Multivariate analysis groups trace elements according to geochemical affinities and natural or anthropogenic sources, thus distinguishing contaminated from uncontaminated samples. The results achieved in this work will help regional and national Authorities for compliance with the EU water policy, especially in assessing the water quality at the river basin scale and its vulnerability to human activities.  相似文献   

Estimating location and size of historical earthquake by combining archaeology and geology in Umm-El-Qanatir,Dead Sea Transform     

Neta Wechsler  Oded Katz  Yehoshua Dray  Ilana Gonen  Shmuel Marco 《Natural Hazards》2009,50(1):27-43

We study the Byzantine-to-Ummayad (6th–8th century) archaeological site of Umm-El-Qanatir, located 10 km east of the Dead Sea Transform (DST) in northern Israel. The site was damaged by an earthquake-induced landslide, and in this work we use slope stability analysis to constrain the historical seismic acceleration that occurred along the northern segment of the DST. Umm-El-Qanatir archaeological site is located on a slope of a canyon and contains evidence for earthquake-related damage, including fallen columns and walls, horizontal shift of heavy masonry blocks, and complete burial of ceramic pots and farming tools beneath fallen ceilings. A water pool that collected spring water is displaced nearly one meter by the landslide. The artifacts from the village and the spring area indicate that people inhabited the site until the middle of the 8th century. We argue that the destruction, which forced the abandonment of Umm-El-Qanatir together with nearby settlements, was associated with the earthquake of January 18, 749 CE. In order to evaluate the ground acceleration related to the above earthquake, we back-analyze the stability of a failed slope, which cut and displaced the water-pool, using slope stability software (Slope/W). The results show that the slope is statically stable and that high values of horizontal seismic acceleration (>0.3 g) are required to induce slope failure. Subsequently, we use the Newmark displacement method to calculate the earthquake magnitude needed to cause the slope failure as a function of distance from the site. The results (attributed to the 749 CE earthquake) show that a M_W > 7.0 earthquake up to 25 km from the site could have induced the studied landslide.  相似文献   

Monitoring ground subsidence induced by salt mining in the city of Tuzla (Bosnia and Herzegovina)   总被引：1，自引：0，他引：1  

F. Mancini  F. Stecchi  M. Zanni  G. Gabbianelli 《Environmental Geology》2009,58(2):381-389

Salt mining induced ground subsidence is a major hazard in the city of Tuzla (Northeastern sector of Bosnia and Herzegovina) and its surroundings since 1950, when solution mining of salt deposits by boreholes began. An analysis of the large (and never before processed) amount of topographical data collected during two periods: from 1956 to the Balkan War, and from 1992 to 2003 has been made. The analysis reveals a cumulative subsidence as high as 12 m during the whole period, causing damage to buildings and infrastructures within an area that includes a large portion of the historical town. Human-induced subsidence, (with rates up to 40 cm/year in the most developed area), has been investigated to recognize the areas affected by the sinking phenomenon and to produce a subsidence hazard. The time series of topographical observations have been enlarged by conducting new surveys in the urban area by modern space-geodesy methodologies, such as static relative GPS (Global Positioning System) and high resolution satellite imageries. The GPS monitoring started in 2004 and detected a decrease in the subsidence rates to 20 cm/year related to the reduction of salt exploitation. There is close correlation between the average subsidence rate and the annual amount of salt extracted.  相似文献   

Channelized and hillslope sediment transport and the geomorphology of mountain belts     

Heinz Schneider  Marco Schwab  Fritz Schlunegger 《International Journal of Earth Sciences》2009,98(1):241-243

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A new Isochirotherium trackway from the Triassic of Vieux Emosson, SW Switzerland: stratigraphic implications     

Marco Avanzini  Lionel Cavin 《Swiss Journal of Geoscience》2009,102(2):353-361

The footprint assemblage of Vieux Emosson, located at 2400 m altitude in the Swiss Alps, was first described in 1982. The assemblage was regarded as Late Ladinian or Carnian in age, but the dating was questioned because the taxa show few affinities with other Triassic assemblages. Here we describe a short trackway with shallow but well-preserved tracks referred to the ichnogenus Isochirotherium, showing affinities with Isochirotherium soergeli and Isochirotherium lomasi. The trackway is present on a piece of slab ex situ lying on a mass of fallen rocks, but the slab can be attributed with confidence to the same level as the main one previously mapped. Preliminary observations in situ and of the footprint casts made in 1979 and deposited in the Natural History Museum of Geneva suggest that none of these are attributable to dinosaurs and that the Vieux Emosson footprints are mainly “track preservation variations” of chirotherian tracks. The occurrence of the ichnogenus Isochirotherium favours an older age, probably Early or Middle Triassic, than previously suggested for the Vieux Emosson tracksite.  相似文献   

Contrasting sediment flux in Val Lumnezia (Graubünden, Eastern Swiss Alps), and implications for landscape development   总被引：1，自引：0，他引：1  

Marco Schwab  Fritz Schlunegger  Heinz Schneider  Gregor Stöckli  Dirk Rieke-Zapp 《Swiss Journal of Geoscience》2009,102(2):211-222

This paper presents qualitative estimates of sediment discharge from opposite valley flanks in the S–N-oriented Val Lumnezia, eastern Swiss Alps, and relates inferred differences in sediment flux to the litho-tectonic architecture of bedrock. The valley flank on the western side hosts the deep-seated Lumnezia landslide where an area of ca. 30 km² has experienced slip rates of several centimetres per year, potentially resulting in high sediment discharge to the trunk stream (i.e. the Glogn River). High slip rates have resulted in topographic changes that are detectable on aerial photographs and measurable with geodetic tools. In contrast, a network of tributary channels dissects the valley flank on the eastern side. There, an area of approximately 18 km² corresponding to < 30% of the surface has experienced a change in the landscape mainly by rock avalanche and rock fall, and the magnitudes of changes are below the calibration limit of digital photogrammetry. We thus infer lower magnitudes of sediment discharge on the eastern tributaries than on the western valley side, where landsliding has been the predominant erosional process. These differences are interpreted to be controlled by the dip-slope situation of bedrock on the western side that favours down-slope slip of material. Morphometric investigations reveal that the western valley side is characterized by a low topographic roughness because this valley flank has not been dissected by a channel network. It appears that high sediment discharge of the Lumnezia landslide has inhibited the establishment of a stable channel network and has largely controlled the overall evolution of the landscape. This contrasts to the general notion that channelized processes exert the first-order control on landscape evolution and formation of relief and needs to be considered in future studies about landscape architecture, drainage network and sediment discharge.  相似文献   

1951-2002年长江流域降水特征   总被引：2，自引：0，他引：2  

苏布达  姜彤  施雅风  Stefan BECKER  Marco GEMMER 《地理学报(英文版)》2004,14(2):204-218

The monthly, seasonal, and annual precipitation trends in the Yangtze river catchment have been detected through analysis of 51 meteorological stations‘ data between 1950-2002 provided by National Meteorological Administration. Results reveal that: 1) Summer precipitation in the Yangtze river catchment shows significant increasing tendency. The Poyanghu lake basin, Dongtinghu lake basin and Taihu lake basin in the middle and lower reaches are the places showing significant positive trends. Summer precipitation in the middle and lower reaches experienced an abrupt change in the year 1992; 2) The monthly precipitation in months just adjoining to summer shows decreasing tendency in the Yangtze river catchment. The upper and middle reaches in Jialingjiang river basin and Hanshui river basin are the places showing significant negative trends; 3) Extreme precipitation events show an increasing tendency in most places, especially in the middle and lower reaches of the Yangtze river catchment.  相似文献