Dleineation and characterization of geomorphological features in a part of lower maharahstra metamorphic plateau using IRS-ID LISS-III Data     

G. P. Obi Reddy  A. K. Maji 《Journal of the Indian Society of Remote Sensing》2003,31(4):241-250

In the present study, an attempt has been made to delineate and characterize the different geomorphic units of Tundiya river catchment in a part of Lower Maharahstra Metamorphic Plateau, north-eastern part of Nagpur district, Maharashtra. The drainage, contour and delineated geological units have been overlaid on IRS-ID LISS III satellite imagery (bands 2,3 and 4) in EASI/PACE analysis system to delineate and characterize different geomorphological units and analysis of their processes based on the field observations. The study area is basically of metamorphic in origin with different geological formations and is influenced by the various fluvio-morphological processes. Based on the satellite data analysis, the distinct geomorphological units viz., table top summits, structural hills, subdued plateau, linear ridges, shallow, moderate and deeply buried foot slopes, shallow valley fills and deep valley fills have been delineated and characterized. The information generated from satellite data in the form of vector layers has been used in GIS to generate geological and geomorphological maps of the study area. The present study demonstrates that IRS-ID LISS-III data in conjunction with geology, drainage and contour parameters to enable detailed evaluation of different geomorphological units and analysis of their processes based on the field observations. The delineated geomorphological units can be utilized for evaluation and management of natural resources and geo-environment on sustainable basis at river catchment level.  相似文献   

西藏夏季降水的季节内变化特征及其影响系统     

次仁央宗  柯宗建  陈丽娟  尼玛吉 《气象》2016,42(11):1342-1350

利用西藏地区1980-2013年夏季降水量资料、NCEP再分析资料等,分析了西藏地区夏季降水主模态季节内变化特征,尤其是盛夏7和8月降水异常对应的大尺度环流特征和影响系统。结果表明:西藏夏季降水存在明显的季节内变化,6和7月降水主模态的时间系数变化具有较好的持续性,而7和8月降水主模态的时间系数的相关关系明显减弱。西藏地区7和8月降水偏多年,西藏地区上游低层纬向风场均呈西风异常,但是水汽来源有差异;同时欧亚中高纬地区对流层中高层环流存在显著差异。西藏7月降水与南亚高压强度存在显著负相关关系,南亚高压偏强/弱时,降水偏少/多。西藏8月降水与南亚高压的位置关系更密切,南亚高压偏南/北,降水偏多/少。  相似文献   

Role of hydrological regime and floodplain sediments in channel instability of the Bhagirathi River,Ganga-Brahmaputra Delta,India     

Sanat Kumar Guchhait  Aznarul Islam  Balai Chandra Das  Nishith Kumar Maji 《自然地理学》2016,37(6):476-510

Abstract

This research deals with the surface dynamics and key factors – hydrological regime, sediment load, and erodibility of floodplain facies – of frequent channel shifting, intensive meandering, and lateral instability of the Bhagirathi River in the western part of the Ganga-Brahmaputra Delta (GBD). At present, the floodplain of the Bhagirathi is categorized as a medium energy (specific stream power of 10–300 W m^?2), non-cohesive floodplain, which exhibits a mixed-load and a meandering channel, an entrenchment ratio >2.2, width–depth ratio >12, sinuosity >1.4, and channel slope <0.02. In the study area, since 1975, four meander cutoffs have been shaped at an average rate of one in every 9–10 years. In the active meander belt and sand-silt dominated floodplains of GBD, frequent shifting of the channel and meander migration escalate severe bank erosion (e.g. 2.5 × 10⁶ m³ of land lost between 1999 and 2004) throughout the year. Remote sensing based spatio-temporal analysis and stratigraphic analysis reveal that the impact of the Farakka barrage, completed in 1975, is not the sole factor of downstream channel oscillation; rather, hydrogeomorphic instability induced by the Ajay–Mayurakshi fluvial system and the erodibility of floodplain sediments control the channel dynamics of the study area.  相似文献   

Transient loading-related settlement of a square foundation on geogrid-reinforced sand     

B. M. Das  A. Maji 《Geotechnical and Geological Engineering》1994,12(4):241-251

Summary Laboratory model test results are presented that determine the effectiveness of using layers of geogrids as reinforcement in sand to reduce the settlement of square surface foundations subjected to transient loading. The model tests were conducted with only one type of geogrid at one relative density of compaction of sand. The maximum intensity of the transient load applied always exceeded the static ultimate bearing capacity of the foundation when supported by unreinforced sand. The settlement reduction factors for various depths of reinforcement have been determined.  相似文献   

Coulomb static stress variations in the Kachchh, Gujarat, India: Implications for the occurrences of two recent earthquakes (M_w= 5.6) in the 2001 Bhuj earthquake region     

Prantik Mandal  R. K. Chadha  I. P. Raju  N. Kumar  C. Satyamurty  R. Narsaiah  A. Maji 《Geophysical Journal International》2007,169(1):281-285

  相似文献   

Effect of surface stress on magneto-elastic surface waves in finitely conducting media     

Debi Pada Acharya  Chaitali Maji 《Acta Geophysica》2007,55(4):554-576

This paper deals with the investigation of the effect of surface stress and conductivity on the propagation of surface wave in isotropic, homogeneous, elastic media under the action of a primary magnetic field. Formulation of the general surface wave propagation problem has been made, and the corresponding frequency equation has been derived. Frequency equations for Rayleigh wave, surface shear wave and Stoneley wave have been deduced from that of general surface wave as special cases. The effects of surface stress and magnetic field on the wave velocities and attenuation factors of Rayleigh wave and surface shear wave are shown by numerical calculations and graphs. Some important wave velocity equations, as obtained by other authors, have been deduced as special cases from the wave velocity equation for Stoneley wave. It is found that the combined effect of surface stress and magnetic field modulates the wave velocity ratios and attenuation factors of Rayleigh wave and surface shear wave to a considerable extent.  相似文献   

Remote Sensing and Geographical Information System for canopy cover mapping     

Ndr Krishna  A K Maji  YVN Krishna Murthy  BSP Rao 《Journal of the Indian Society of Remote Sensing》2001,29(3):107-113

Availability of remote sensing data from earth observation satellites has made it convenient to map and monitor land use/land cover at regional to local scales. A land cover map is very critical for a various planning activities including watershed planning. The spectral and spatial resolutions are major constraints for mapping the crop resources at microlevel. The cropping pattern zones have been mapped using the false color composite, physiography, irrigation and toposheets. The IRS LISS-III data is classified into various categories depending on spectral reflectance from crop canopy and are overlaid on cropping zones map. The re-classified resultant map provides land use/land cover information including dominant cropping systems. The canopy cover is estimated monthly considering the crop calendar for the area.  相似文献   

An overview on geochemistry of Proterozoic massif-type anorthosites and associated rocks     

A. K. Maji  A. Patra  P. Ghosh 《Journal of Earth System Science》2010,119(6):861-878

A critical study of 311 published WR chemical analyses, isotopic and mineral chemistry of anorthosites and associated rocks from eight Proterozoic massif anorthosite complexes of India, North America and Norway indicates marked similarities in mineralogy and chemistry among similar rock types. The anorthosite and mafic-leucomafic rocks (e.g., leuconorite, leucogabbro, leucotroctolite, anorthositic gabbro, gabbroic anorthosite, etc.) constituting the major part of the massifs are characterized by higher Na₂O + K₂O, Al₂O₃, SiO₂, Mg# and Sr contents, low in plagioclase incompatible elements and REE with positive Eu anomalies. Their δ ¹⁸O‰ (5.7–7.5), initial ⁸⁷Sr/⁸⁶Sr (0.7034–0.7066) and ɛ _Nd values (+1.14 to +5.5) suggest a depleted mantle origin. The Fe-rich dioritic rocks occurring at the margin of massifs have isotopic, chemical and mineral composition more close to anorthosite-mafic-leucomafic rocks. However, there is a gradual decrease in plagioclase content, An content of plagioclase and X_Mg of orthopyroxene, and an increase in mafic silicates, oxide minerals content, plagioclase incompatible elements and REE from anorthosite-mafic-leucomafic rocks to Fe-rich dioritic rocks. The Fe-rich dioritic rocks are interpreted as residual melt from mantle derived high-Al gabbro melt, which produced the anorthosite and mafic-leucomafic rocks. Mineralogically and chemically, the K-rich felsic rocks are distinct from anorthosite-mafic-leucomafic-Fe-rich dioritic suite. They have higher δ ¹⁸O values (6.8–10.8‰) and initial ⁸⁷Sr/⁸⁶Sr (0.7067–0.7104). By contrast, the K-rich felsic suites are products of melting of crustal precursors.  相似文献   

Assessment of flexural analysis applied to the Sumatra-Java subduction zone     

R. T. Ratheesh Kumar  Tanmay K. Maji  Rajesh R. Nair 《Journal of Earth System Science》2010,119(5):717-730

Indian Ocean subduction zone is one of the most active plate margins of the globe as evident from its vast record of great magnitude earthquake and tsunami events. We use Bouguer admittance (Morlet isostatic response function) in Sumatra-Java subduction zones comprising both the subduction and over-riding plates to determine the lithospheric mechanical strength variations. We determine effective elastic thickness (T _e ) for five oceanic windows (size 990 × 990 km²) by analyzing the admittance using Bouguer gravity and bathymetry data. The results show bimodal T _e values < 20 km for Sumatra and 20−40 km for Java. The lower bimodal values obtained for Sumatra appears to correlate well with the zones of historical seismicity. This is in sharp contrast with Java subduction zone, which shows higher T _e values (20–40 km) and apparently associated with low magnitude earthquakes. We suggest a strong and wide interseismic coupling for Sumatra between the subducting and over-riding plates, and deeper mantle contributing to low strength, shallow focus — high magnitude seismicity and vice versa for Java, leading to their seismogenic zonation.  相似文献   

Head-on collisions of two types of dust-acoustic solitons in a magnetized quantum plasma     

M. K. Ghorui  U. K. Samanta  T. K. Maji  P. Chatterjee 《Astrophysics and Space Science》2014,352(1):159-169

  相似文献