Peak ground motion predictions in India: an appraisal for rock sites   总被引：1，自引：0，他引：1  

Sankar Kumar Nath  Kiran Kumar Singh Thingbaijam 《Journal of Seismology》2011,15(2):295-315

Proper selection and ranking of Ground Motion Prediction Equations (GMPEs) is critical for successful logic-tree implementation in probabilistic seismic hazard analysis. The present study explores this issue in predicting peak ground accelerations at the rock sites in India. Macroseismic intensity data complemented with limited strong ground-motion recordings are used for the purpose. The findings corroborate the possible conformity between the GMPEs developed for tectonically active shallow crust across the globe. On the other hand, the relevant GMPEs in the intraplate regions cluster into two different groups with the equations of lower ranks catering to higher ground motions. The earthquakes in the subduction zones have significant regional implications. However, affinity in the ground-motion attenuations between the major interface events (M _W > 7.4) in Andaman-Nicobar, Japan and Cascadia, respectively, is noted. This can be also observed for the intraslab events in the Hindukush and Taiwan respectively. Overall, we do not observe any significant advantage with the equations developed using the regional data. These findings are expected to be useful in probabilistic seismic hazard analysis across the study region.  相似文献   

An Environmental Threshold of Soil Test P and Degree of P Saturation of Brazilian Oxisols     

Amlan Kumar Ghosh  Joyce Barbosa  Ivo Ribeiro da Silva 《洁净——土壤、空气、水》2011,39(5):421-427

To develop P management guidelines for poultry litter application in Oxisols of Brazil, the relationship between water soluble P (WSP), soil test P (STP), and degree of P saturation (DPS) needs to be established. The study examined this relationship in Oxisols of Brazil receiving poultry litter. Soils were analyzed for Mehlich‐1 P (M1‐P), WSP, P fractions, P sorption index (PSI), and P saturation based on Mehlich‐1 extractable P, Al, Fe (DPS_M1), and PSI (DPS_PSI). Surface water bodies in the catchment area were examined for inorganic and total P. All the surface water bodies in the catchment area of the sampled plots were highly enriched in inorganic and organic P. Enrichment of soil P fractions following poultry litter application followed the order HCl‐bound > NaOH‐bound > NaHCO₃‐bound fraction. M1‐P was correlated to labile (NaHCO₃‐P_i), and stable P pools (NaOH‐P and HCl‐P) and reflected the cumulative P accumulation in these soils. P saturation indices increased with cumulative P addition and increasing M1‐P. WSP increased with increasing DPS and a change point was noticed at 23% DPS_PSI (equivalent to DPS_M1 of 16.5%) corresponding to M1‐P of 44.5 mg P kg^?1, which could be regarded as threshold for P loss in these soils.  相似文献   

Holocene climate variability from lake sediment core in Larsemann Hills,Antarctica     

Pawan Govil  Abhijit Mazumder  Anoop Tiwari  Sandeep Kumar 《Journal of the Geological Society of India》2011,78(1):30-35

A sediment core (L2) from Larsemann Hills, Antarctica was analyzed for Biogenic Silica (BSi), Sand (%) and Total Organic Carbon (TOC). The 78 cm core length represents the time span of ∼8.3 cal ka BP. The values of BSi from the core show prominent high productivity from ∼8.3 to ∼6 cal ka BP in comparison to less productivity in mid-late Holocene (∼6 cal ka BP to recent). Moreover, high sand (%) infers the glacio-fluvial deposition from ∼8.3 to ∼5 cal ka BP TOC shows little variation through out the core, except in the upper ∼10 cm (∼4 cal ka BP) part wherein it is comparatively high. The increased TOC in the upper part of the core possibly indicates presence of algal mat due to exposure of the lake to the ice free (glacier free) conditions.  相似文献   

Hydrouranium anomalies as an effective tool in exploration of concealed unconformity related U-deposit in Srisailam sub-basin,Andhra Pradesh — Case study from Chitrial area     

M. B. Verma  P. S. Dandele  G. Nagendra Babu  K. Umamaheswar  P. B. Maithani 《Journal of the Geological Society of India》2011,78(5):468-476

Relationship of hydro-uranium anomalies (2-649 ppb) vis-à-vis underlying uranium ore body has been attempted based on seventy nine water samples collected from the exploratory boreholes on the northern periphery of Srisailam sub basin, Nalgonda district, A.P. Water table is hosted in the granitoid aquifer which underlies the cover rocks of Srisailam Formation. TDS (total dissolved salt) range from 123 to 1088 ppm (x^? = 329 ppm) and analyzed >500 ppm in eight samples. Water samples show a strong positive correlation of TDS with Cl^? (r=0.90), Na⁺ (r=0.82), Mg (r=0.80) and a moderate positive correlation with Sr (r=0.48) and Ca (r=0.70). Low value (<0.4) of Normalised Magnesium (NMg) indicates that host rock aquifer has not undergone chloritisation. Accumulate contour plan of uranium ore body shows NW-SE trend and coincides with the hydro-uranium contour. Correlation sections of ore body display true as well as false hydro-uranium anomalies in N-S and E-W profiles. Hydro-uranium anomalies owe their origin to uranium cations, dissolved from the mineralized horizon in to groundwater. Hydro-geochemical orientation survey carried out at Chitrial plateau may be applied regionally in the Srisailam sub basin as an effective tool to explore the concealed unconformity type uranium mineralization below Srisailam Formation.  相似文献   

Groundwater resources management through flow modeling in lower part of Bhagirathi — Jalangi interfluve,Nadia, West Bengal     

Sudhir Kumar  Subrata Halder  D. C. Singhal 《Journal of the Geological Society of India》2011,78(6):587-598

Groundwater utilization in Nadia district, West Bengal has been subjected to rapid exploitation in the wake of increasing urbanization and production of agricultural commodities. It is, therefore, necessary to evaluate the existing trend and availability of groundwater in time and space and its movement for proper planning in future. In the present study, an attempt has been made develop a groundwater management model using Visual MODFLOW software. The groundwater flow model for the study area was formulated by using input hydrogeological data and appropriate boundary conditions. The groundwater flow pattern of the study area indicates the occurrence of base flow which feed both the Rivers Bhagirathi and Jalangi throughout the year. The computed hydraulic heads were calibrated by comparing with observed groundwater level data for years 2004 to 2006 and were verified with the data of 2007. The outcome of modeling shows that this model can be used for prediction purpose in the future by updating input boundary conditions and hydrologic stresses during the preceding year. The model optimized unit draft for deep tube well as 556.5 m³/day and the same for shallow tube well as 41 m³/day keeping the existing tube well structures in running condition and maintaining the present and recent past trends of groundwater level. The model can be further improved if more spatial and temporal input parameters are available and can be incorporated into the model for more realistic characterization of groundwater flow.  相似文献   

Chemical weathering of the Indo-Gangetic alluvium with special reference to release of fluoride in the groundwater,Unnao district,Uttar Pradesh   总被引：1，自引：0，他引：1  

S. Kumar  A. Saxena 《Journal of the Geological Society of India》2011,77(5):459-477

In the central part of Indo-Gangetic alluvium in the Unnao district, Uttar Pradesh there are many pockets where groundwater shows high fluoride content. Drinking of fluorinated ground water has effected a large population and in many villages more than 80% of the population is suffering from fluorosis. The source of this fluoride appears to be the alluvial sediments deposited in the geological past as no hard rock terrain is present in the nearby areas. The area is dominantly made up of mud with pockets of sand. The sand fraction is made up of quartz, plagioclase, microcline, muscovite and biotite along with some accessory minerals like garnet, epidote, chlorite, tourmaline, hornblende, kyanite and a few opaque minerals. Moreover, the fluoride content in the groundwater varies both spatially and with depth indicating a sporadic occurrence. The surface water is devoid of high content of fluoride but is reported in hand pumps and in the dug wells. This paper deals with the geochemical study of the sediments up to a depth of 45m as most of the hand pumps are up to this depth to understand the source of fluoride. ¹⁴C dates of calcretes have suggested that the 45 m thick succession must have been formed in about 45000 years.  相似文献   

Structural analyses of the crystalline rocks between Dirang and Tawang,West Kameng district,Arunachal Himalaya     

Hari B. Srivastava  Vaibhava Srivastava  Rajesh K. Srivastava  Chandra Kant Singh 《Journal of the Geological Society of India》2011,78(1):45-56

In Kameng Valley of Arunachal Pradesh, the crystalline rocks of Se La Group of Higher Himalaya are thrust over the Lesser Himalayan rocks of Dirang Formation, Bomdila Group along the Main Central Thrust and exhibit well preserved structures on macro- to microscopic scales. Detailed analysis of structures reveals that the rocks of the area have suffered four phases of deformation D₁, D₂, D₃ and D₄. These structures have been grouped into (i) early structures (ii) structures related to progressive ductile thrusting and (iii) late structures. The early structures which developed before thrusting formed during D₁ and D₂ phases of deformation, synchronous to F₁ and F₂ phases of folding respectively. The structures related to progressive ductile shearing developed during D₃ phase of deformation, when the emplacement of the crystalline rocks took place over the rocks of Dirang Formation along the Main Central Thrust. Different asymmetric structures/kinematic indicators developed during this ductile/brittle-ductile regime suggest top-to-SSW sense of movement of the crystalline rocks of the area. D₄ is attributed to brittle deformation. Based on satellite data two new thrusts, i.e. Tawang and Se La thrusts have been identified parallel to Main Central Thrust, which are suggestive of imbricate thrusting. Strain analysis from the quartz grains of the gneissic rocks reveals constriction type of strain ellipsoid where k value is higher near the MCT, gradually decreases towards the north. Further, the dynamic analysis carried out on the mesoscopic ductile and brittle-ductile shear zones suggest a NNE-SSW horizontal compression corresponding to the direction of northward movement of Indian Plate.  相似文献   

Numerical Modeling and Spatial Moment Analysis of Thermal Fronts in a Coupled Fracture-Skin-Matrix System     

N.?NatarajanEmail author  G.?Suresh Kumar 《Geotechnical and Geological Engineering》2011,29(4):477-491

In this study, the behavior of thermal fronts along the fracture is studied in the presence of fracture-skin in a coupled fracture-matrix system. Cold water is injected into the fracture, which advances gradually towards production well, while extracting heat from the surrounding reservoir matrix. The heat conduction into the fracture-skin and the rock-matrix from the high permeability fracture is assumed to be one dimensional perpendicular to the axis of fluid flow along the fracture. Constant temperature cold water is injected through an injection well at the fracture inlet. The fluid flow takes place along the horizontal fracture which ensures connectivity between the injection and production wells. Since the rock-matrix is assumed to be tight, the permeability of fracture-skin as well as the rock-matrix is neglected. The present study focuses on the heat flux transfer at the fracture-skin interface as against the earlier studies on fracture-matrix interface, and the sensitivity of additional heterogeneity in the form of fracture skin in a conventional fracture-matrix coupled system is studied. The behavior of thermal fronts for various thermal conductivity values of the fracture-skin and rock-matrix is analyzed. Spatial moment analysis is performed on the thermal distribution profiles resulting from numerical studies in order to investigate the impact on mobility and dispersion behavior of the fluid in the presence of fracture-skin. The presence of fracture skin affects the heat transfer significantly in the coupled fracture-matrix system. The lower order spatial moments indicate that the effective thermal velocity increases with increase in skin thermal conductivity and a significant thermal dispersion is observed at the inlet of the fracture owing to the high thermal conductivity of the fracture-skin at the early stages. Furthermore the higher spatial moments indicate that the asymmetricity increases with decrease in skin thermal conductivity unlike the case with half fracture aperture and fluid velocity and the kurtosis is maximum with higher skin thermal conductivity which implies enhanced heat extraction from the fracture-skin into the fracture. Results suggest that the amount of heat extraction by the circulating fluid within the fracture from the reservoir not only depends on the rock-matrix module of the reservoir characteristics but also the fracture-skin characteristics of the system and subsequently influence the reservoir efficiency.  相似文献   

Comparison of Two Sample Preparation Methods for X‐Ray Fluorescence Spectrometry in the Determination of Ni and Cr     

Surendra P. Verma  Rosalinda González‐Ramírez  Rodolfo Rodríguez‐Ríos 《Geostandards and Geoanalytical Research》2011,35(2):183-192

Pressed powder pellets and fused beads or glass disks are routinely used in X‐ray fluorescence spectrometry for the determination of major and trace elements, respectively, in geological materials. In order to evaluate the performance of these two sample preparation methods, we determined Ni and Cr concentrations of fourteen RMs from Japan, France and South Africa, and eighty‐five igneous and three sedimentary rock samples from Mexico in both powder pellets and glass beads. We also computed new values of statistical parameters for RMs from an outlier‐based multiple‐test method and compared them with the literature mean and confidence limit values. The results showed that the multiple‐test method provided more reliable central tendency and dispersion parameters for RMs than those obtained previously from the two or three standard deviation method, or from robust methods. The powder pellet and fused bead sample preparation methods provided consistent results for Ni and Cr at concentration levels > 50 μg g^?1 in this application; for lower concentration levels, however, these methods showed somewhat greater differences. For quantitative comparisons, both ordinary and weighted least‐squares linear regression models were used to show that the two sample preparation methods provided generally unbiased results.  相似文献   

The study of indoor radon in the urban dwellings using plastic track detectors     

M. Shakir Khan  M. Zubair  Deepak Verma  A. H. Naqvi  Ameer Azam  M. K. Bhardwaj 《Environmental Earth Sciences》2011,63(2):279-282

Radon and its progeny have been recognized as one of the major contributors to the natural radiation and health hazards in the human dwellings. Even lung cancer is expected if it is present in enhanced levels beyond maximum permissible limit. This paper reports the measurements of indoor radon and its progeny in the urban dwellings of the Etah district of Uttar Pradesh province in Northern India using the cellulose nitrate (LR-115 type-II) plastic track detectors. It is found that the values of radon concentration vary from 3.52 to 248.64 Bq m⁻³ with a standard deviation of 69.19. The values of radon progeny concentration vary from 0.38 to 26.88 mWL with a standard deviation of 7.48. The effective dose has been calculated and found to vary from 0.05 to 3.76 mSv year⁻¹ with a standard deviation of 1.05. The lifetime fatality risk is found to vary from 0.04 × 10⁻⁴ to 2.90 × 10⁻⁴. The results have been compared with the results reported in the rural areas of the same district.  相似文献