A unified earthquake catalogue for South Asia covering the period 1900–2014     

Nath  Sankar Kumar  Mandal  Suman  Das Adhikari  Manik  Maiti  Soumya Kanti 《Natural Hazards》2017,85(3):1787-1810

Seismicity analysis is very much pertinent for Indian subcontinent and its adjoining region which is seismically active including many great earthquakes associated with collision and subduction tectonics in the northern, north-eastern part of the subcontinent and in the Andaman and Nicobar Island. An earthquake catalogue has been generated for South Asia covering the period 1900–2014 by compiling the records of earthquake occurrences from International Seismological Center, Global Centroid Moment Tensor (GCMT), US Geological Survey, India Meteorological Department and published literature. The uniform magnitude scaling in moment magnitude M _W,GCMT is achieved through connecting relationships between different magnitude types. These relationships are derived by orthogonal standard regression analysis on available data pairs. The derived relationships have been compared with the existing equations already reported by others. The catalogue is subsequently subjected to a seismicity declustering algorithm to identify the foreshocks, main-shocks and aftershocks. The catalogue thus compiled is envisaged to be a useful resource for seismotectonic and seismic hazard studies in the region.

  相似文献   

Geology and geochemistry of Pachmarhi dykes and sills,Satpura Gondwana Basin,central India: problems of dyke-sill-flow correlations in the Deccan Traps     

Hetu C. Sheth  Jyotiranjan S. Ray  Ranjini Ray  Loÿc Vanderkluysen  John J. Mahoney  Alok Kumar  Anil D. Shukla  Partha Das  Subhrashis Adhikari  Bikashkali Jana 《Contributions to Mineralogy and Petrology》2009,158(3):357-380

Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers and higher TiO₂ contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow correlations even with extensive geochemical fingerprinting.  相似文献   

Influence of discontinuity structure on rock fragmentation by blasting     

G. R. Adhikari  R. N. Gupta 《Geotechnical and Geological Engineering》1989,7(3):239-248

  相似文献   

Climate and water balance change among public,private, and tribal lands within Greater Wild land Ecosystems across North Central USA     

Adhikari  Arjun  Hansen  Andrew J. 《Climatic change》2019,152(3-4):551-567

Climatic Change - The remaining wildlands in the North Central US include varying proportions of public, private, and tribal lands across water balance ecotones. These wildlands may be highly...  相似文献   

Quantifying Four Decades of Changes in Land Use and Land Cover in India’s Kailash Sacred Landscape: Suggested Option for Priority Based Patch Level Future Forest Conservation     

G. Singh  M. S. Sarkar  A. Pandey  S. Lingwal  I. D. Rai  B. S. Adhikari  G. S. Rawat  R. S. Rawal 《Journal of the Indian Society of Remote Sensing》2018,46(10):1625-1635

Effective quantification of land cover changes remains a challenge in Himalayan hills and mountains, and has a colossal value addition for natural resource management. Here we present a new robust method for classifying land cover vegetation at physiognomic scale along steep elevational gradients from ~?200 to ~?7000 masl in the Kailash Sacred Landscape, Western Himalaya, India along with four decades of land use and land cover changes (1976–2011) using remote sensing techniques coupled with intensive ground surveys. Results show that forest cover loss was minimum ca 7.14% of existing forest in 1976; but, however forest fragmentation is high especially in montane broad-leaved and subtropical needle leaved forests. This change largely impacted the quality of valuable tree species such as Quercus spp. Post 1976, continuous migration forced conversion of high altitude agricultural lands into grasslands and scrublands. Human settlement expansion was high especially in low altitudinal range valleys between 1000 and 2000 masl and has increased 6.76 fold since 1976, leading to high forest fragmentation in spite of reduced agriculture area in the landscape. Our physiognomic level classified land cover map will be a key for forest managers to prioritize conservation zones for protecting this unique forest land.  相似文献   

Tracking IMF Fluctuations Nearby Sun Using Wavelet Analysis: Parker Solar Probe First Encounter Data     

Gautam  S. P.  Silwal  A.  Bashyal  A.  Chaudhary  K.  Khanal  M.  Ale  B.  Adhikari  B.  Poudel  P.  Karki  M.  Chapagain  N. P. 《Geomagnetism and Aeronomy》2022,62(1-2):138-150

Geomagnetism and Aeronomy - The Parker Solar Probe (PSP) satellite was launched by NASA in 2018 to study the Sun’s environment from a closer distance than any spacecraft has ever reached...  相似文献   

A Neotectonic based geomorphic analysis using remote sensing data to delineate potential areas of hydrocarbon exploration: Cachar area,Assam     

Subhobroto Mazumder  Kalyan Adhikari  Durga Shanker Mitra  Samiran Mahapatra  Krishan Kumar Singh Pangtey 《Journal of the Geological Society of India》2016,88(1):87-97

TheAssamArakan fold thrust belt has highly deformed folded units of Tertiary sediments bounded by eastward dipping thrust slices with a convexity towards west. In the Tripura-Cachar region, this folded belt is characterized by the occurrence of wide synclines and narrow anticlines that hosts a number of hydrocarbon producing fields. In the Cachar area of Assam, most of these fields occur in the culmination of anticlinal structures. Other wells drilled in analogous structural settings are found to be dry. In this paper a neotectonic based geomorphic analysis is carried out to delineate a fault network and geomorphic highs in Cachar area as expressions of sub-surface structures which had subsequently been validated by available geophysical data. Of these geomorphic highs, those that are in the synclinal areas are believed to represent subtle sub-surface structural highs. Synclinal structures associated with NNE-SSW faults might be considered interesting for hydrocarbon exploration and are subsequently categorized following their degree of confidence for exploration of hydrocarbon. Additionally, a genetic model of the structures in the region is also proposed.  相似文献   

A simplified method for unified buckling and free vibration analysis of pile-supported structures in seismically liquefiable soils     

S. Bhattacharya  S. Adhikari  N.A. Alexander 《Soil Dynamics and Earthquake Engineering》2009

In seismic-prone zones with liquefiable deposit piles are routinely used to support structures (buildings/bridges). In this paper, a unified buckling and dynamic approach is taken to characterize this vibration. The pile–soil system is modelled as Euler–Bernoulli beam resting against an elastic support with axial load and a pile head mass with rotary inertia. The emphasis here is to obtain a simple expression that can be used by practicing engineers to obtain the fundamental frequency of the structure–pile–soil system. An approximate method based on an equivalent single-degree-of-freedom model has been proposed. Natural frequencies obtained from the exact analytical method are compared with approximate results. Proposed expressions are general as they are functions of non-dimensional parameters. It is shown that this simplified method captures the essential design features such as: (a) the continuous reduction of the first natural frequency of the structure–pile–soil system due to progressive reduction of soil stiffness due to liquefaction; (b) the reduction in the axial load-carrying capacity of the pile due to instability caused by liquefaction. The results derived in this paper have the potential to be directly applied in practice due to their simple yet general nature. An example problem has been taken to demonstrate the application of the method.  相似文献   

Fabrication of Nanoparticle-Doped Polyvinyl Alcohol-Cellulose Acetate Membrane and Characterization of the Surface Enhancement     

Sathish Raam Ravichandran  Chitra Devi Venkatachalam  Mothil Sengottian  Sarath Sekar  Bhavya Shri Subramaniam Ramasamy  Sakthivel Elangovan  Siddharth Thorali Sivakumar  Shanmuga Sundaram Subramanian 《洁净——土壤、空气、水》2023,51(3):2100305

In the present study, nanocomposite polymeric membranes are fabricated using polyvinyl alcohol (PVA), cellulose acetate (CA) as polymers, and dimethyl sulfoxide (DMSO) as the solvent. To enhance the performance of the membrane, nanoparticles like TiO₂, CaO, CdO, and ZrO are added to the polymeric solution and the doped polymeric solution is cast on a glass plate. Nine combinations of membranes are fabricated with two different concentrations (0.1% and 0.2%) of nanoparticles. The basic properties of the membranes such as density, porosity, viscosity, permeability, pure water flux, and water content are studied for the samples. Membrane pore structure and surface properties are identified and it is found that doping nanoparticles on the surface of membranes improve mechanical strength, stability, pore size, etc., allowing the membranes to perform better in extreme industrial-level effluent treatment applications. High-resolution scanning electron microscopy (SEM) shows the homogeneous dispersion of ZrO, TiO₂, CaO, and CdO nanoparticles on the surface of the PVA-CA membrane. The doping of nanoparticles on the PVA-CA membrane results in improved mechanical strength and good chemical oxidation stability. In comparison, the PCD-TiO₂ sample shows high thermal stability and oxidation stability at high temperatures until 200°C, which has a high potential for treating industrial effluents.  相似文献   

基于台网目录分析研究汶川8.0级地震余震时空分布特征   总被引：3，自引：2，他引：1       下载免费PDF全文

李丽  Lok Bijaya Adhikari  李纲  高福旺 《地球物理学报》2018,61(5):1797-1805

2008年5月12日汶川M_S8.0地震主震发生后至2012年5月12日,我国地震台网在龙门山断裂区域内（102°E-105°E,30°N-34°N）共记录93837个地震事件,其中80995次事件含有深度信息.本文以台网地震目录为主要研究对象,分析了汶川地震余震序列的时空分布与演化特征.与构造活动密切相关的余震频次-震级关系变化显示,与主震断裂活动直接相关的余震活动在主震后4个月内基本结束.余震释放能量的空间分布及演化分析显示,在主震后6~24 h即有可能捕获未来余震区的大致展布乃至余震发展趋势.  相似文献