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111.
112.
Effect of dust storm on ocean color and snow parameters 总被引:1,自引:0,他引:1
Vinay K. Kayetha Senthil Kumar J. Anup K. Prasad Guido Cervone Ramesh P. Singh 《Journal of the Indian Society of Remote Sensing》2007,35(1):1-9
The present study clearly shows the influence of dust storms on chlorophyll bloom in the offshore region of the Arabian Sea,
with a time lag of few days, during the pre-monsoon season. Various satellite derived parameters over the Arabian Sea, Himalayan
and Tibet snow covered regions show large changes due to the influence of dust storms. The MODIS snow albedo gives unreliable
values under the influence of dust storms due to increase in the aerosol loading over these regions and snow albedo product
must be used in combination with snow pixel counts during the dust storm season. A detailed study is required for the quantitative
evaluation of dust storms on the chlorophyll blooms in the Arabian Sea region and on the snow parameters in the Himalayan
region. 相似文献
113.
Full-scale Modelling of Falling Rock Protection Barriers 总被引:1,自引:0,他引:1
Full-scale impact tests, carried out to evaluate the behaviour of flexible falling rock protection barriers, are described
and relevant results presented and discussed. Falling rock protection barriers, which may be numbered among passive measures
against rockfall, are designed to intercept and stop falling rocks by dissipation of impact energies through the elasto-plastic
deformation of a system made up of metallic nets and supporting and connecting components. The testing programme involved
models of barriers subjected to the impact of free-falling blocks of kinetic energy ranging from 500 to 5,000 kJ. The experimental
test site, set-up in Fonzaso (Italy), and the experimental procedure were developed according to the new European testing
standards (ETAG 027) on falling rock protection kits. The paper is aimed at presenting an extensive and high quality database,
which can be extremely useful for a better understanding of the actual response of such structures and for any subsequent
analytical and numerical modelling. 相似文献
114.
Remote sensed data for automatic detection of land-use changes due to human activity in support to landslide studies 总被引:1,自引:1,他引:1
Slope instability studies appear to recognize a number of potential superficial slide-producing agents, which may be directly
detected and monitored with Earth Observation (EO) data. The main objective of this work is to use conventional EO data and
automatic techniques for providing land-use change maps useful in landslide prevention. The idea is to use the detection of
changes in areas already involved in landslide events as a precursory sign of variations in the equilibrium status of the
slope, independently from other natural triggering events, such as rain and seismic events. Attention is focused on man-induced
surface changes, such as deforestation, urban expansion and construction of artificial structures.
A historical set of 20 multi-temporal Landsat TM images, covering the period 1987–2000, was analyzed using a supervised change
detection technique on a test site affected by slope instability phenomena located in the Abruzzo region in Southern Italy.
A change image is obtained by comparing year-specific thematic map pairs. It contains useful information not only on the place
where a transition occurred, but also on the specific classes involved in the transitions between two different years. The
full set of change images is used to extract class-conditional transition probabilities, to evaluate variations in specific
class distribution and the total number of changed pixels in time. Four classes and their transitions were considered in the
analysis: (1) arboreous land, (2) agricultural land, (3) barren land, and (4) artificial structures.
The quantitative analysis of the class-joint transition probability values of some specific class-transitions that may worsen
slope stability showed that in an area prone to landslides the probability of landslide re-activation or first activation
is higher where changes have occurred. Although based on a limited number of known events, such a result encourages extensive
experimentation of the proposed technique on better documented landslide test sites. 相似文献
115.
Seyyedeh Halimeh Hashemi Azizi Payman Rezaee Mahdi Jafarzadeh Guido Meinhold Seyyed Reza Moussavi Harami Mehdi Masoodi 《Chemie der Erde / Geochemistry》2018,78(3):340-355
In Central Iran, the mixed siliciclastic?carbonate Nakhlak Group of Triassic age is commonly seen to have a Cimmerian affinity, although it shows considerable resemblances with the Triassic Aghdarband Group in far northeastern Iran, east of Kopeh-Dagh area, with Eurasian affinity. The Nakhlak Group is composed of the Alam (Late Olenekian?Anisian), Baqoroq (Late Anisian??Early Ladinian), and Ashin (Ladinian??Early Carnian) formations consisting mainly of volcanoclastic sandstone and shale and fossiliferous limestone. The Baqoroq Formation contains also metamorphic detritus. Sandstone petrofacies reflect the detrital evolution from active volcanism to growing orogen and again active volcanism. Textural and modal analyses of volcanic lithic fragments from the Alam Formation reflect the eruption style and magma composition of a felsic to intermediate syn-sedimentary arc activity. The detrital modes of the Baqoroq Formation sediments suggest a recycled orogenic source followed by arc activity in a remnant fore-arc basin. The sandstone samples from the Ashin Formation demonstrate a continuity of felsic to intermediate arc activity. Major and trace element concentrations of the Nakhlak Group clastic samples support sediment supply from first-cycle material and felsic magmatic arc input. The enrichment in LREE, the negative Eu anomalies, and the flat HREE patterns indicate origination from the old upper continental crust and young arc material. The chemical index of alteration (CIA ~51–70 for sandstone and 64–76 for shale samples) indicates medium degrees of chemical weathering at the source. Petrographical and geochemical evidence together with facies analysis constructed the following depositional conditions for the Nakhlak Group sediments: In the Olenekian, a fore-arc shallow to deep marine depositional basin developed that later was filled by recycled and arc-related detritus and changed into a continental basin in the Anisian. Ladinian extension let to a deepening of the basin. With respect to the similarities between the Nakhlak and Aghdarband (NE Iran) groups and unusual present-day position of the Nakhlak Group with no stratigraphic connection to the surrounding area, the development of first a fore-arc basin and later change into a back-arc depositional basin in close relation with the Aghdarband basin at the southern Eurasian active margin in the Triassic are here proposed. Understanding the basin development recorded in the Nakhlak Group provides constraints on the closure history of Palaeotethys and of the tectonic evolution of early Mesozoic basins at the southern Eurasian margin before the Cimmerian Orogeny. 相似文献
116.
In north-eastern Greece the mid-greenschist facies Makri Unit and the anchizonal Melia Formation belong to the eastern Circum-Rhodope Belt that forms the uppermost tectonostratigraphic unit of the Rhodope metamorphic nappe pile. The two metasedimentary successions had different source areas, although they now lie in close proximity in the Rhodope Massif. The U-Pb isotopic ages of detrital zircons from a metasandstone of the Makri Unit analysed using LA-SF-ICP-MS and SHRIMP-II gave age clusters at ca. 310-290 Ma and at ca. 240 Ma for magmatic zircons, which may have been derived from Carboniferous-Permian basement rocks of the Thracia Terrane (Lower Tectonic Unit of the Rhodope Massif) that subsequently underwent Triassic rifting. The youngest detrital zircon grains found so far indicate that the metasedimentary succession of the Makri Unit, or at least parts of it, cannot be older than Late Triassic. By contrast, clastic sedimentary rocks of the Melia Formation contain the primary detrital mineral assemblage of epidote, zoisite, garnet, and phengitic mica, which is absent in the Makri Unit, and clearly points to metamorphic rocks being the major source for these sediments. U-Pb analyses of detrital zircons gave a prominent age cluster at ca. 315-285 Ma for magmatic zircons. Inherited cores indicate the involvement of Pan-African and Late Ordovician-Early Silurian crustal sources during Late Carboniferous-Early Permian igneous event(s). Moreover, U-Pb detrital zircon geochronology indicates that the Melia Formation cannot be older than latest Middle Jurassic. We suggest that the Melia Formation was deposited in front of a metamorphic nappe pile with Rhodopean affinities in Tithonian or Cretaceous times. Both the Makri Unit and the Melia Formation have been tectonically juxtaposed from different sources to their present location during Balkan and Alpine orogenic processes. 相似文献
117.
Domenico Cosentino Paola Cipollari Letizia Di Bella Alessandra Esposito Costanza Faranda Guido Giordano Elsa Gliozzi Massimo Mattei Ilaria Mazzini Massimiliano Porreca Renato Funiciello 《Quaternary Research》2009,72(1):143-155
The historical site of the Monte Mario lower Pleistocene succession (Rome, Italy) is an important marker of the Pliocene/Pleistocene boundary. Recently, the Monte Mario site was excavated and restudied. A spectacular angular unconformity characterizes the contact between the Monte Vaticano and the Monte Mario formations, which marks the Pliocene/Pleistocene boundary. Biostratigraphical analyses carried out on ostracod, foraminifer, and calcareous nannofossil assemblages indicate an Early Pliocene age (topmost Zanclean, 3.81–3.70 Ma) for the underlying Monte Vaticano Formation, whereas the Monte Mario Formation has been dated as early Pleistocene (Santernian, 1.66–1.59 Ma). Palaeomagnetic analyses point to C2Ar and C1r2r polarity chrons for the Monte Vaticano and the Monte Mario formations, respectively. The Monte Mario Formation consists of two obliquity-forced depositional sequences (MM1 and MM2) characterized by transgressive systems tracts of littoral marine environments at depths, respectively, of 40–80 m and 15–20 m. The data obtained from foraminifer and ostracod assemblages allow us to reconstruct early Pleistocene relative sea-level changes near Rome. At the Plio/Pleistocene transition, a relative sea-level drop of at least 260 m occurred, as a result of both tectonic uplift of the central Tyrrhenian margin and glacio-eustatic changes linked to early Pleistocene glaciation (Marine Isotope Stage 58). 相似文献
118.
Cesare Comina Renato Maria Cosentini Gabriele Della Vecchia Sebastiano Foti Guido Musso 《Acta Geotechnica》2011,6(4):195-203
Monitoring transport of dissolved substances in soil deposits is particularly relevant where safety is concerned, as in the
case of geo-environmental barriers. Geophysical methods are very appealing, since they cover a wide domain, localising possible
preferential flow paths and providing reliable links between geophysical quantities and hydrological variables. This paper
describes a 3D laboratory application of electrical resistivity tomography (ERT) used to monitor solute transport processes.
Dissolution and transport tests on both homogeneous and heterogeneous samples were conducted in an instrumented oedometer
cell. ERT was used to create maps of electrical conductivity of the monitored domain at different time intervals and to estimate
concentration variations within the interstitial fluid. Comparisons with finite element simulations of the transport processes
were performed to check the consistency of the results. Tests confirmed that the technique can monitor salt transport, infer
the hydro-chemical behaviour of heterogeneous geomaterials and evaluate the performances of clay barriers. 相似文献
119.
Guido G. Weigend 《Geoforum》1975,6(2)
The Danube River, Europe's longest west of the Soviet Union, connects central and southeastern Europe. It flows through areas of great diversity of climates and land forms. Navigation has, in fact, been hindered by fluctuating water levels, ice, and defiles. Primarily for political reasons the river, prior to the middle of the 20th century, had never been a viable link of transportation and communication. Since the second world war, however, effective internationalization of the river, extensive navigation improvement projects, construction of dams and hydroelectric power plants, and greatly accelerated economic development in the Danube River basin in general, all point toward the river becoming one of Europe's principal axes and regional bonds. 相似文献
120.
The characteristics of the strong ground motion accelerograms from the 1999 Kocaeli earthquake are investigated in detail
in this study. The emphasis is on the comparison of the response spectra for the fault normal (FN) and fault parallel (FP)
components of the ground motions. The results show that the near-fault records with directivity effects characterize themselves
with increased base shear demands rather than increased displacement demands for both the FN and FP components and a narrower
velocity sensitive region for the FN component. This study also shows that the effectiveness of base isolation may vary from
site to site and for a given site, from component to component. The site effects in the Marmara region during the 1999 Kocaeli
earthquake are examined. Site amplifications are predicted by the classical spectral ratio (CSR) and the receiver function
(RF) methods. The CSR method gives higher estimates for the site amplifications compared to the RF method and is in better
conformity with the observed damage during the Kocaeli earthquake. The districts of Istanbul that are especially susceptible
to site amplification hazard are determined. It is apparent from the results that the site amplification hazard risk is the
highest for Avcilar and Bakirkoy districts. This study also shows that for sites which have the risk of soil amplification
for long-period structures, liquefaction may not be beneficial as a natural base isolator, and may result in shifting the
eigenperiod of the low- and mid-rise structures to the critical periods with high site amplifications. This may be especially
the case for Avcilar and Bakirkoy districts. In Fatih, Bakirkoy, and Cekmece districts, the predominant period of the ground
motion is calculated to be very close to the eigenperiods of the typical residential buildings. Therefore, these three districts
are expected to experience heavier damages in future earthquakes due to resonance effects. 相似文献