Fractal study of seismicity in order to characterize the various tectonic blocks of North-east Himalaya,India     

P. N. S. Roy  Suparna Chowdhury  Partha Sarkar  Saroj Kumar Mondal 《Natural Hazards》2015,77(1):5-18

North-eastern Himalaya is said to be one of the world most complex geological set-up with different kinds of seismotectonic systems. Region has experienced two of the world’s strongest earthquakes, such as Shillong earthquake of 1897 known as Assam earthquake and subsequent 1950 earthquake in Arunachal Pradesh, both of with magnitude of 8.7, and also several other strong earthquakes. Various techniques have been applied to understand the past strong earthquake mechanism as well as hazard estimation carried out for future earthquake. Fractal correlation dimension (D _c) is being used in this study with the seismicity for the period 1961 to recent for understanding the pattern of seismic hazard. The entire area has been divided into four major tectonic blocks, and each block event was divided into consecutive fifty events window for seeing spatiotemporal patterns. After comparing the patterns, we have identified that Block of Eastern Himalaya near Main Central Thrust, Main Boundary Thrust, north of Kopili lineament and Block of Shillong plateau near Dauki fault are having relatively intense clustering of events in recent times, which may be identified as the zones of most potential to have a strong event.  相似文献   

Integrated mineral magnetic and lithologic studies to delineate dynamic modes of depositional conditions in the Leh valley basin, Ladakh Himalaya, India     

S. J. Sangode  Suman Rawat  D. C. Meshram  N. R. Phadtare  N. Suresh 《Journal of the Geological Society of India》2013,82(2):107-120

We present here lithofacies and mineral magnetic results from a ～50 m thick composite record of fluvial, lacustrine and aeolian facies within the Leh valley basin of Indus River in Ladakh Himalaya. Mineral magnetic studies decipher interplay of two contrasting sediment sources viz., the unimodal ferrimagnetic source derived from Ladakh batholithic glacial domain and mixed ferri-to antiferromagnetic source derived from Indus sedimentary sequence. The lithofacies variability expresses dynamic changes in the depositional regimes controlled by base level fluctuations that are governed by the interaction of basin fill conditions and the response to Late Quaternary climatic perturbations. A three stage evolution of the Leh valley basin is proposed after comparison to other characteristic lithofacies changes within the valley as: (I) the basin under-fill conditions marked by fluvial and fluvio-lacustrine phase till ～24m (～64 Ka OSL age) above modern base level followed by (II) predominantly varved, glacio-lacustrine, basin overfill phase till 38m (～28 Ka) gradually passing into an aeolian phase; and (III) basin incision that began at the earliest Holocene warming. Advancement and retreat of glaciers from the transverse valleys, attributed to climatic oscillations, appears to have greatly controlled the basin-fill conditions in the Leh valley. The present approach demonstrates its larger scope in recording the Late Quaternary response of individual valley basins to delineate local and regional attributes of climate change in the Himalayan and Karakoram region.  相似文献   

Insight into adsorption equilibrium,kinetics and thermodynamics of lead onto alluvial soil     

B. Das  N. K. Mondal  R. Bhaumik  P. Roy 《International Journal of Environmental Science and Technology》2014,11(4):1101-1114

In the present study, adsorption of lead (II) ions from aqueous solution by alluvial soil of Bhagirathi River was investigated under batch mode. The influence of solution pH, sorbent dose, initial lead (II) concentration, contact time, stirring rate and temperature on the removal process were investigated. The lead adsorption was favored with maximum adsorption at pH 6.0. Sorption equilibrium time was observed in 60 min. The equilibrium adsorption data were analyzed by the Freundlich, Langmuir, Dubinin–Radushkevich and Temkin adsorption isotherm models. The kinetics of lead (II) ion was discussed by pseudo first-order, pseudo second-order, intra-particle diffusion, and surface mass transfer models. It was shown that the adsorption of lead ions could be described by the pseudo second-order kinetic model. The activation energy of the adsorption process (E _a) was found to be ?38.33 kJ mol^?1 using the Arrhenius equation, indicating exothermic nature of lead adsorption onto alluvial soil. Thermodynamic parameters, such as Gibbs free energy (?G ⁰), the enthalpy (?H ⁰), and the entropy change of sorption (?S ⁰) have also been evaluated and it has been found that the adsorption process was spontaneous, feasible, and exothermic in nature. The results indicated that alluvial soil of Bhagirathi River can be used as an effective and low cost adsorbent to remove lead ions from aqueous solutions.  相似文献   

Goldschmidt Conference 2013, Florence,Italy     

Sisir K. Mondal 《Journal of the Geological Society of India》2014,83(1):104-105

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http://www.sciencedirect.com/science/article/pii/S1674987113000340     

Suman Kilaru  Bandaru Karunakar  Goud Vijay  Kumar Rao 《地学前缘(英文版)》2013,4(6):717-728

Regional surface gravity data and global satellite magnetic data have been utilized to generate a preliminary model of the crustal structure along a southwest-northeast profile （Gadra-Fatehpur） through western Rajasthan.The study area represents the western part of the Indian continental landmass which has undergone several major episodes of repeated subduction/collision,plume traces and rifting from Archaean to recent times.The temporal and spatial relationship between the various geotectonic provinces is quite complex,thereby limiting the emergence of a suitable crustal structure model for this region.Exposures of the Malani Igneous Suite （MIS）,a product of bimodal volcanism （～780 Ma）,and considered to be the third largest felsic magmatic province of the world,is evident along the profile and also to the southwest of the study area.The easternmost part of the profile is close to the DAFB （Delhi Aravalli Fold Belt）,a Proterozoic orogenic belt.This study probes the geometry of the different crustal units in terms of density and susceptibility variations in order to decipher the imprints of the major tectonic processes the region has undergone.In order to decipher the crustal geometry of the Gadra-Fatehpur profile,two NW-SE gravity and magnetic profile vertical sections （A-A＇ in the south and B-B＇ in the north） are modelled on the basis of the constraints provided from previous seismic models.The crustal model of the Gadra-Fatehpur profile is composed of alluvium,Tertiary sediments,MIS,Marwar Supergroup,low-density layers （LDLs） and the middle-lower crustal layers,with a distinct change in configuration from the southwest to northeast.The Moho dips from SW to NE,the MIS in the SW gives way to the thick pile of the Marwar Supergroup to the NE.The evolution of MIS has been suggested to have occurred as a consequence of delamination of the upper mantle.LDLs are incorporated in Gadra-Fatehpur model.In the SW,LDL （2550 kg/m3） lies below the MIS in the NE,another LDL （2604 kg/m3） is depicted below the mid-crustal layer.  相似文献   

Point Discharge Current During a Solar Eclipse     

S. S. De  Suman Paul  S. Barui  P. Hazra  D. Kala  D. K. Haldar  A. Ghosh  G. Guha 《Earth, Moon, and Planets》2013,111(1-2):79-87

The effect of solar eclipse of July 22, 2009, obscuring up to 91 %, upon the value of point discharge current (PDC) has been reported in this paper. The observation had been taken from Kolkata (Lat. 22.56°N, Long. 88.5°E). During the eclipse period, significant variations in the magnitude of PDC were observed than their average value for the same period in other days. The average value of the PDC for the successive ±10 days adjacent to the solar eclipse day was about 2.253 A.U. (Arbitrary Unit), while the minimum value showed about 2.242 A.U. at the time of greatest phase at 06:26.4 IST (Indian Standard Time). The results are mainly interpreted in terms of changes of the conductivity of the medium during the solar eclipse.  相似文献   

Detection of 2009 Leonid,Perseid and Geminid Meteor Showers through its effects on Transmitted VLF Signals     

S. S. De  B. K. De  Pinaki Pal  B. Bandyopadhyay  S. Barui  D. K. Haldar  Suman Paul  Minu Sanfui  Goutami Chattopadhyay 《Astrophysics and Space Science》2011,332(2):353-357

The detection of 2009 Leonid, Perseid and Geminid meteor showers over Agartala, Tripura, India (Lat: 23.0° N, Long: 91.4° E) will be reported here by using two VLF receivers tuned to subionospheric transmitted VLF signals at the frequency 16.4 kHz from Aldra Island, Norway (Lat: 66.42° N, Long: 13.13° E) and the other at 18.2 kHz from Vijayananarayanam, India (Lat: 8.4° N; Long: 77.7° E). The received signals exhibited their peak values on November 17, 2009 when ZHR (Zenithal Hourly Rate) was highest. Some typical variations which are observed in the records of amplitude during the 2009 Leonid, Perseid and Geminid meteor showers will be presented in this paper.  相似文献   

Studies on the Effects of 2009 Leonid Meteor Shower on Subionospheric Transmitted VLF Signals and Vertical Electric Potential Gradient     

S. S. De  B. Bandyopadhyay  S. Barui  Suman Paul  D. K. Haldar  D. De  B. K. De  S. Chattopadhyay  A. K. Kundu 《Earth, Moon, and Planets》2012,108(2):111-121

The effects of 2009 Leonid Meteor Shower upon the two VLF subionospheric transmitted signals and vertical electric potential gradient from the ground surface have been studied from Kolkata (Lat: 22.56°N, Long: 88.5°E) on November 17, 2009. The received signals showed their peak values when ZHR (Zenithal Hourly Rate) was highest. Some typical variations in the outcome of these measurements during the meteor showers will be presented in this paper.  相似文献   

Comparative assessment of crisp and fuzzy analytic hierarchy process for multi-criteria decision making in geographic information system (GIS)-based site suitability analysis for relocation of tigers     

Laxmikant Sharma  Suman Sinha  Mahendra Singh Nathawat 《国际地球制图》2013,28(2)

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Stress drop and its relation to tectonic and structural elements for the meizoseismal region of great 1905 Kangra earthquake of the NW Himalaya     

Kumar  Naresh  Yadav  Dilip K.  Mondal  S. K.  Roy  P. N. S. 《Natural Hazards》2013,69(3):2021-2038

Natural Hazards - Investigations of micro- and low-magnitude earthquakes in the Kangra-Chamba region of the NW Himalaya were performed to evaluate the relationship between earthquake source,...  相似文献