Textural and Mineralogical Characteristics of the Beach Sands of Tamil Nadu, Southern India     

C.G. Chandrasekaran  K.V. Muralidharan  K. Joshi Nirmal Kumar 《Gondwana Research》2001,4(4):588

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Monitoring Urban Landscape Dynamics Over Delhi (India) Using Remote Sensing (1998–2011) Inputs     

Richa Sharma  P. K. Joshi 《Journal of the Indian Society of Remote Sensing》2013,41(3):641-650

Urbanization is increasingly becoming a widespread phenomenon at all scales of development around the globe. Be it developing or developed nations, all are witnessing urbanization at very high pace. In order to study its impacts, various methodologies and techniques are being implemented to measure growth of urban extents over spatial and temporal domains. But urbanization being a very dynamic phenomenon has been facing ambiguities regarding methods to study its dynamism. This paper aims at quantifying urban expansion in Delhi, the capital city of India. The process has been studied using urban land cover pattern derived from Landsat TM/ETM satellite data for two decades (1998–2011). These maps show that built-up increased by 417 ha in first time period (1998–2003) and 6,633 ha during next period (2003–2011) of study. For quantification of metrics for urban expansion, the Urban Landscape Analysis Tool (ULAT) was employed. Land cover mapping was done with accuracy of 92.67 %, 93.3 % and 96 % respectively for years 1998, 2003 and 2011. Three major land covers classes mapped are; (i) built-up, (ii) water and (iii) other or non-built-up. The maps were then utilized to extract degree of urbanization based on spatial density of built-up area consisting of seven classes, (i) Urban built-up, (ii) Suburban built-up,(iii) Rural built-up, (iv) Urbanized open land, (v) Captured open land, (vi) Rural open land and (vii) Water. These classes were demarcated based on the urbanness of cells. Similarly urban footprint maps were generated. The two time maps were compared to qualitatively and quantitatively capture the dynamics of urban expansion in the city. Along with urbanized area and urban footprint maps, the new development areas during the study time periods were also identified. The new development areas consisted of three major categories of developments, (i) infill, (ii) extension and (iii) leapfrog.  相似文献   

Cartosat-1 derived DEM (CartoDEM) towards Parameter Estimation of Microwatersheds and Comparison with ALTM DEM     

Rajashree Vinod Bothale  A. K. Joshi  Y. V. N. Krishnamurthy 《Journal of the Indian Society of Remote Sensing》2013,41(3):487-495

Hydrologic analysis of microwatersheds is essential for water resources planning at large scale. Space based input for decentralized planning at panchayat level use high resolution DEM. Drainage and slope play important role in planning and Digital Elevations Models (DEM) are widely being used for estimation of hydrologic parameters which are useful as input for hydrologic models. The estimates vary as per resolution and type of DEM. This paper evaluates the suitability of DEM derived through Cartosat-1 satellite stereo data(CartoDEM) for hydrologic parameter estimation of microwatersheds and compares the results with Airborne Laser Terrain Mapper (ALTM) based DEM data. Comparison is based on the hydrologic parameters delineated in Geographical Information System. Microwatersheds are delineated and drainage length extracted using two different cell sizes for both DEMs. Correctness Index, Figure of Merit, visual comparison, Percent within buffer and Junction comparison method, compared extracted river network. Average watershed slope is calculated using three different methods. CartoDEM derived drainage is comparable with ALTM derived drainage. There is high correlation between Carto5 and Caro10 DEMs in terms of drainage delineation and slope calculation. Average watershed slope vary as per calculation methods but average channel slope value (S3) although less, is comparable across DEMs.  相似文献   

Measurements of radon flux and soil-gas radon concentration along the Main Central Thrust, Garhwal Himalaya, using SRM and RAD7 detectors     

Abhay Anand Bourai  Sunita Aswal  Anoop Dangwal  Mukesh Rawat  Mukesh Prasad  Nagendra Prasad Naithani  Veena Joshi  Rakesh Chand Ramola 《Acta Geophysica》2013,61(4):950-957

Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. ²²²Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then ²²²Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m^?3 with geometrical mean value of 302 ± 84 Bq·m^?3. Th significance of this work is its usefulness from radiation protection point of view.  相似文献   

Role of attenuation relationship in shaping the seismic hazard     

K. Mohan  A. Joshi 《Natural Hazards》2012,60(2):649-670

Attenuation relationships are commonly used for engineering studies to estimate the peak ground acceleration values. This paper presents the role of attenuation relationship in defining the seismic hazard in an area. It is seen that the seismic hazard in an area, which is calculated using attenuation relationships, is mostly controlled by the type of attenuation relationship used in the study. The present work aims to study the effect of attenuation relationship on seismic hazard study. In the present work, seismic hazard maps have been prepared in the seismically very active northeast Himalaya using the approach given by Joshi and Patel (Tectonophysics 283:289–310, 1997). The attenuation relationships of Jain et al. (2000), Sharma (2000), Joyner and Boore (Bull Seism Soc Am 71:2011–2038, 1981) and Abrahamson and Litehiser (Bull Seism Soc Am 79:549–580, 1989) have been considered in the present study. Among all considered attenuation relationships, the Abrahamson and Litehiser (Bull Seism Soc Am 79:549–580, 1989) attenuation relationship gives the least root mean square error between the recorded and calculated peak ground acceleration values. Therefore, the same has been used to define attenuation characteristic of the region. The mean and standard deviation of peak ground acceleration values at all the observation points due to above-mentioned attenuation relationships in the NE Himalayas are calculated. The study shows that the Zone III covers an area of 81,000 km² and Zone II of 96,000 km² in the map prepared using the mean peak ground acceleration values, whereas the area of Zone IV increases by 40,000 km² when the map is prepared by adding the standard deviation values in the mean peak ground acceleration values, and only Zone II is left with 183,000 km² when the standard deviation values are subtracted from the mean. This high standard deviation is due to the difference in the peak ground acceleration values obtained from different events. This study shows that a rigorous test needs to be done for selecting attenuation relationship for any hazard study in a given area.  相似文献   

Near-field and far-field simulation of accelerograms of Sikkim earthquake of September 18, 2011 using modified semi-empirical approach     

A. Joshi  Pushpa Kumari  Sandeep Singh  M. L. Sharma 《Natural Hazards》2012,64(2):1029-1054

The semi-empirical approach for modeling of strong ground motion given by Midorikawa (Tectonophysics 218:287?C295, 1993) has been modified in the present paper for component wise simulation of strong ground motion. The modified approach uses seismic moment in place of attenuation relation for scaling of acceleration envelope. Various strong motion properties like directivity effect and dependence of peak ground acceleration with respect to surface projection of source model have been studied in detail in the present work. Recently, Sikkim earthquake of magnitude 6.9 (M _w ) that occurred on September 18, 2011 has been recorded at various near-field and far-field strong motion stations. The modified semi-empirical technique has been used to confirm the location and parameters of rupture responsible for this earthquake. Strong motion record obtained from the iterative modeling of the rupture plane has been compared with available strong motion records from near as well as far-field stations in terms of root mean square error between observed and simulated records. Several possibilities of nucleation point, rupture velocity, and dip of rupture plane have been considered in the present work and records have been simulated at near-field stations. Final selection of model parameters is based on root mean square error of waveform comparison. Final model confirms southward propagating rupture. Simulations at three near-field and twelve far-field stations have been made using final model. Comparison of simulated and observed record has been made in terms of peak ground acceleration and response spectra at 5?% damping. Comparison of simulated and observed record suggests that the method is capable of simulating record which bears realistic appearance in terms of shape and strong motion parameters. Present work shows that this technique gives records which matches in a wide frequency range for Sikkim earthquake and that too from simple and easily accessible parameters of the rupture plane.  相似文献   

Determination of Q β(f) in Different Parts of Kumaon Himalaya from the Inversion of Spectral Acceleration Data     

A. Joshi  P. Kumar  M. Mohanty  A. R. Bansal  V. P. Dimri  R. K. Chadha 《Pure and Applied Geophysics》2012,169(10):1821-1845

This paper presents the results of a modified two-step inversion algorithm approach to find S wave quality factor Q _β(f) given by Joshi (Bull Seis Soc Am 96:2165–2180, 2006). Seismic moment is calculated from the source displacement spectra of the S wave using both horizontal components. Average value of seismic moment computed from two horizontal components recorded at several stations is used as an input to the first part of inversion together with the spectra of S phase in the acceleration record. Several values of the corner frequency have been selected iteratively and are used as inputs to the inversion algorithm. Solution corresponding to minimum root mean square error (RMSE) is used for obtaining the final estimate of Q _β(f) relation. The estimates of seismic moment, corner frequency and Q _β(f) from the first part of inversion are further used for obtaining the residual of theoretical and observed source spectra which are treated as site amplification terms. The acceleration record corrected for the site amplification term is used for determination of seismic moment from source spectra by using Q _β(f) obtained from first part of inversion. Corrected acceleration record and new estimate of seismic moment are used as inputs to the second part of the inversion scheme which is similar to the first part except for use of input data. The final outcome from this part of inversion is a new Q _β(f) relation together with known values of seismic moment and corner frequency of each input. The process of two-step inversion is repeated for this new estimate of seismic moment and goes on until minimum RMSE is obtained which gives final estimate of Q _β(f) at each station and corner frequency of input events. The Pithoragarh district in the state of Uttarakhand in India lies in the border region of India and Nepal and is part of the seismically active Kumaon Himalaya zone. A network of eight strong motion recorders has been installed in this region since March, 2006. In this study we have analyzed data from 18 local events recorded between March, 2006 and October, 2010 at various stations. These events have been located using HYPO71 and data has been used to obtain frequency-dependent shear-wave attenuation. The Q _β(f) at each station is calculated by using both the north-south (NS) and east-west (EW) components of acceleration records as inputs to the developed inversion algorithm. The average Q _β(f) values obtained from Q _β(f) values at different stations from both NS and EW components have been used to compute a regional average relationship for the Pithoragarh region of Kumaon Himalaya of form Q _β(f)?=?(29?±?1.2)f ^{(1.1 ± 0.06)}.  相似文献   

Geomorphometry and fractal dimension of a riverine badland in Maharashtra     

Veena Joshi  Devidas Tambe  Gorakh Dhawade 《Journal of the Geological Society of India》2009,73(3):355-370

One of the most serious limitations in studying the surface morphometry of a badland landscape is the nonavailability of a very fine resolution data which is essential for such types of studies. Local relief of most of the badlands in India and also from other parts of the world exhibit limited relief amplitude, often within a few meters. The paper reports a case study carried out in a riverine badland formed along the Western Deccan Trap Region. An attempt has been made in the present paper to extract the morphometric variables of the landscape from the DEMs derived from a high resolution field generated data, because the accuracy of the DEM derived values are dependent on the pixel resolution of the DEM from which they are generated. The size of the pixel resolution should be fixed differently for different landscapes depending on the landscape process in the area. The local relief of the area is around 10 m and for such types of landscapes the topographical maps and also the web-available DEMs are of very coarse resolutions which are not suitable for the analysis. Therefore two well defined tributary catchments were chosen from the area under investigation and theodolite surveys were carried out, contours were generated with 10 cm interval, DEMs were derived by using Arc GIS software. SRTM (Shuttle Radar Topography Mission) 90 m resolution data were utilized to generate DEM for the whole basin. Hypsometric and the drainage basin parameters were extracted from these data by using the same software. Fractal dimension of the whole basin and the sample basins were also obtained for the same data. The morphometric data generated were used to understand the geomorphic processes operating in the area.  相似文献   

Grain surface features of alluvial sediments of upper Pravara Basin and their environmental implications     

Veena U. Joshi 《Journal of the Geological Society of India》2009,74(6):711-722

Quartz sand grains obtained from a deeply gullied topography along the banks of two tributaries of River Pravara in Godavari Basin, Maharashtra have been examined with a scanning electron microscope (SEM) in order to make the environmental interpretations of these deposits. The sediments reveal features resulting from mechanical grinding as well as from chemical alteration. Conchoidal fractures, cleavage planes, grooves, v-shaped indentations etc are the mechanical features documented on the grains whereas solution pits of varying sizes and intensity, precipitation surfaces, oriented v-pits, solution crevasses and etching are the features of diagenetic origin. Few sand grains show the evidence of wind transported sediments. Several evidence indicate that the samples have undergone digenetic changes. Few grains exhibit the features of intense chemical breakdown. The overall assemblages of the grain surface features suggest that the samples have been subjected to subaqueous transport for a considerable period of time. The chemical features such as etching, solution pits or semi circular arcuate steps that are found in abundance in these grains are due to the dissolution of the sediments in a low energy fluviatile environment, such as in floodplain region.  相似文献   

Body Wave Crustal Attenuation Characteristics in the Garhwal Himalaya,India     

Sanjay S. Negi  Ajay Paul  Anand Joshi  Kamal 《Pure and Applied Geophysics》2015,172(6):1451-1469

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