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排序方式: 共有274条查询结果,搜索用时 93 毫秒
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A passive teleseismic experiment (TOR), traversing the northern part of the Trans-European Suture Zone (TESZ) in Germany, Denmark and Sweden, recorded data for tomography of the upper mantle with a lateral resolution of few tens of kilometers as well as for a detailed study of seismic anisotropy. A joint inversion of teleseismic P-residual spheres and shear-wave splitting parameters allows us to retrieve the 3D orientation of dipping anisotropic structures in different domains of the sub-crustal lithosphere. We distinguish three major domains of different large-scale fabric divided by first-order sutures cutting the whole lithosphere thickness. The Baltic Shield north of the Sorgenfrei–Tornquist Zone (STZ) is characterised by lithosphere thickness around 175 km and the anisotropy is modelled by olivine aggregate of hexagonal symmetry with the high-velocity (ac) foliation plane striking NW–SE and dipping to NE. Southward of the STZ, beneath the Norwegian–Danish Basin, the lithosphere thins abruptly to about 75 km. In this domain, between the STZ and the so-called Caledonian Deformation Front (CDF), the anisotropic structures strike NE–SW and the high-velocity (ac) foliation dips to NW. To the south of the CDF, beneath northern Germany, we observe a heterogeneous lithosphere with variable thickness and anisotropic structures with high velocity dipping predominantly to SW. Most of the anisotropy observed at TOR stations can be explained by a preferred olivine orientation frozen in the sub-crustal lithosphere. Beneath northern Germany, a part of the shear-wave splitting is probably caused by a present-day flow in the asthenosphere. 相似文献
144.
The Mahanadi River is one of the largest river systems in the east coast of Indiaand the estuary drains and communicates with the Bay of Bengal. The seasonallyvarying fresh water river discharge and the intrusion of salt water from the baydepend on the flow associated with the semi-diurnal component of the astronomicaltide (dominated by M2 component). A numerical model has been developed tosimulate and study the salinity structure, velocity profile, flow and circulation patternand have been compared with the observed data. A reasonably good agreement isnoticed between the model simulations and the observations. The model result hasbeen utilised to compute sediment load transport to the estuary channel over a tidalcycle as well as on a monthly time scale. The sediment load transport owing to monthlyclimatological rainfall is discussed and it is inferred that a dynamic equilibrium existson a long-term over good/bad monsoons. 相似文献
145.
Jaroslava Plomerová Vladislav Babuška Libuše Ruprechtová Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1984,28(1):56-66
mam mm ua a na Pn, Pg, Sn u Sg nu¶rt;u u au -ma. aa, m ¶rt; amu 5° m numa ua¶rt;a ¶rt;am mu a na n au ma¶rt;amu u mu anmau , uu m n u ma¶rt;am¶rt;a. am nmau a uu m anmau mmu aua. 相似文献
146.
Y. S. Babu Rao Jagan Mohan A. Bhattacharya 《Journal of the Indian Society of Remote Sensing》1983,11(1):75-78
Mapping of the Archaean, Precambrian and Permocarboniferous sedimentary formations in the northern and southern parts of Godavari river covering parts of Adilabad and Karimnagar districts through photointerpretation technique, has been found to be fairly accurate and reliable. Their unique photo characters and other recognition elements are briefly described in this paper. 相似文献
147.
A. Sridharan T. G. Soosan Babu T. Jose B. M. Abraham 《Geotechnical and Geological Engineering》2006,24(5):1163-1179
Due to the high demand for rubble and aggregates for construction purposes, rubble quarries and aggregate crushers are very
common. Out of the different quarry wastes, quarry dust is one, which is produced in abundance. About 20–25% of the total
production in each crusher unit is left out as the waste material-quarry dust. Bulk utilization of this waste material is
possible through geotechnical applications like embankments, back-fill material, sub-base material and the like. It becomes
a useful additive to the natural soil to improve its strength characteristics. For the above applications one of the important
engineering properties is the shear strength. The purpose of the present investigation is to understand the shear strength
behavior of quarry dust and soil-quarry dust mixes. 相似文献
148.
V. Purnachandra Rao Pratima M. Kessarkar R. Nagendra E. V. S. S. K. Babu 《Journal of Earth System Science》2007,116(6):525-536
Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in
the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur
Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus
of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed
between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments.
A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present.
Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P2O5 content of the phosphorites ranges from 18 to 26%. The CaO/P2O5, Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, Al, K, Fe, and Ti are low.
We suggest that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at intertidal
conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then
reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey coloured phosphate
clasts at water depths between 180 and 320m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture.
Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts
onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability
of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites. 相似文献
149.
Bhardwaj Pandit G. L. Sivakumar Babu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(2):152-168
Traditional reliability-based design methodologies often involve selection of design which is of lowest cost and satisfies safety requirements. But, this design is sensitive to variation in statistics of input parameters (noise parameters) and might become unsatisfactory if an underestimation of coefficient of variation of input parameters is made. A relatively new design methodology known as robust geotechnical design (RGD) is applied for the case of reinforcement of rock slope using end-anchored rock bolts. This ensures selection of a cost-effective and safe design for which probability of failure (Pf) of reinforced rock slope is least sensitive to the noise parameters. Reliability-based RGD approach involves evaluation of Pf for each design with different possible noise parameters. Finding Pf for the complex geotechnical structure is computationally expensive, and thus an augmented radial basis function-based response surface is used as a surrogate to the finite element model of rock slope. This response surface, being very efficient, also performs well for a range of values of noise parameters. Later, minimum distance algorithm is applied to obtain a cost-effective and robust design. Finally, a comparison is made in the costs between two robust designs obtained for different target probability of failure for the same rock slope. 相似文献
150.