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41.
The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events 总被引:1,自引:0,他引:1
D.V. Reddy P. Nagabhushanam Devender Kumar B.S. Sukhija P.J. Thomas Anand K. Pandey R.N. Sahoo G.V. Ravi Prasad K. Datta 《Tectonophysics》2009,474(3-4):463-472
Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon (14C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. 14C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by 14C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, 14C dating could constrain the 1548 AD event though not distinctly. Further studies using combined 14C and OSL dating may better constrain the seismo-chronology of the study region. 相似文献
42.
A detailed analysis of depositional history of Miocene sediments and various effects which are governed for creation of accommodation
space as well as the processes of sedimentation inherent to the depositional system at that period is described in this work.
The early Miocene clastic sediments are deposited in prograding environment where sediment supply exceeds the accommodation
space available. The accommodation space created due to basin subsidence and source area upliftment due to local and regional
tectonic activity in the basin. In the early Miocene time, the Assam shelf major transgression occurred and several minor
transgression followed. There was wide spread deposition of the fluvial Tipam sandstones. In Miocene time due to thrust loading
and flexure subsidence, accommodation space was created for deposition of the sediments. The Tipam Sandstone is deposited
by cyclic deposition of fining upward sequence in a fluvial to brackish water environment of braided river processes. The
mechanism of braided rivers is also discussed in which it laterally expanded, leaving sheet like or wedge — shaped deposits
of channel and bar complexes preserving only minor amounts of flood plain material. 相似文献
43.
The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana
basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-,
medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates
the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained
sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy
analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic
states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total
thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between
number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari
Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential
subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make
the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally
migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances. 相似文献
44.
In this paper, we have constructed mesonic stiff fluid cosmological models in five dimensional LRS Bianchi type-I and Bianchi
type-VI0 space times in general theory of relativity. Some physical and geometrical properties of the models are discussed. 相似文献
45.
In this paper, we constructed some five dimensional LRS Bianchi type-I string cosmological models based on Lyra geometry and studied some physical and geometrical properties of the models. 相似文献
46.
Five dimensional LRS Bianchi type-I effective stiff fluid cosmological models in scalar tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) are constructed. Further, some physical and geometrical features of these models are discussed. 相似文献
47.
Late Quaternary environmental and climate changes registered in lacustrine sediments of the Serra Sul de Carajás,south‐east Amazonia 下载免费PDF全文
48.
Exact solutions are obtained in (4+1) dimensions for plane symmetric and cylindrically symmetric inhomogeneous spacetimes. In the former case the three space depends on time only while the metric corresponding to the extra dimension is dependent on space as well as time coordinates. The cylindrically symmetric nonstatic solutions for the perfect fluid have no singularity near the axis, but show big bang type of singularity in the finite past. One of the classes of such solutions satisfies the barotropic equation of state of the form =p. Static solutions with cylindrically symmetric solutions are also obtained in 5 dimensions. 相似文献
49.
An attempt has been made to identify plausible groundwater potential zones (GWPZ) based on Grey Analytic Hierarchy Process Method (Grey-AHP) using integrated remote sensing and geographic information system. Grey-AHP combines the advantages of classical analytic hierarchy process and grey clustering method for accurate estimation of weight coefficients. The method also examines the effectiveness of GWPZ identification process. The proposed methodology has been applied to the Hirakud canal command area, Odisha (India). Feature layers [e.g. soil type, geology] are utilized for groundwater potential index (GWPI) calculation. The resulting GWPI map has been classified into three GWPZ namely: good, moderate and poor. Effectiveness based on grey clustering method is found to be in between ‘better’ and ‘common’ classes. Value of coefficient of determination (R2 = 0.865) supports the obtained effectiveness evaluation result. This analysis demonstrates the potential applicability of the methodology for a general aquifer system. 相似文献
50.
Satya Narayan Soumyashree Debasis Sahoo Ujjawal Kumar Vipin Kumar Pathak T. J. Majumdar 《国际地球制图》2017,32(4):351-366
The present study deals with classical problem of edge detection in potential field data over complex tectonic regime for both shallower and deeper sources, simultaneously. Balanced horizontal derivative (BHD) technique is a latest edge detection concept which delineates edges using balancing of amplitude responses for both shallower and deeper sources. The BHD technique has been validated by comparing with total horizontal derivative (THD) technique. Initially, three different synthetic models have been generated with spherical, cylindrical and vertical prismatic objects at different depths and corresponding gravity responses have been enhanced using BHD and THD techniques. Structural features have been delineated from EIGEN6C4 free-air gravity data using THD and BHD techniques over a part of the Bay of Bengal. Major lineaments have been identified in N–S direction followed by those identified along the NE–SW, NW–SE and E–W directions. Both studies of synthetic models and real gravity data reveal that BHD is an advanced technique than THD. 相似文献