Calibration of foundation movements for AASHTO LRFD bridge design specifications     

Naresh C. Samtani  John M. Kulicki 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3):185-194

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Estimation of Q p and Q s of Kinnaur Himalaya     

Naresh Kumar  Shonkholen Mate  Sagarika Mukhopadhyay 《Journal of Seismology》2014,18(1):47-59

The attenuation characteristics of the Kinnaur area of the North West Himalayas were studied using local earthquakes that occurred during 2008–2009. Most of the analyzed events are from the vicinity of the Panjal Thrust (PT) and South Tibetan Detachment Thrust, which are well-defined tectonic discontinuities in the Himalayas. The frequency-dependent attenuation of P and S waves was estimated using the extended coda normalization method. Data from 64 local earthquakes recorded at 10 broadband stations were used. The coda normalization of the spectral amplitudes of P and S waves was done at central frequencies of 1.5, 3, 6, 9, and 12 Hz. Q _p increases from about 58 at 1.5 Hz to 706 at 12 Hz, and Q _s increases from 105 at 1.5 Hz to 1,207 at 12 Hz. The results show that the quality factors for both P and S waves (Q _p and Q _s) increase as a function of frequency according to the relation Q?=?Q _o f ⁿ , where Q _o is the corresponding Q value at 1 Hz frequency and “n” is the frequency relation parameter. We obtained Q _p?=?(47?±?2)f ^(1.04±0.04) and Q _s?=?(86?±?4)f ^(0.96±0.03) by fitting power law dependency model for the estimated values of the entire study region. The Q ₀ and n values show that the region is seismically very active and the crust is highly heterogeneous. There was no systematic variation of values of Q _p and Q _s at different frequencies from one tectonic unit to another. As a consequence, average values of these parameters were obtained for each frequency for the entire region, and these were used for interpretation and for comparison with worldwide data. Q _p values lie within the range of values observed for some tectonically active regions of the world, whereas Q _s values were the lowest among the values compared for different parts of the world. Q _s/Q _p values were >1 for the entire range of frequencies studied. All these factors indicate that the crust is highly heterogeneous in the study region. The high Q _s/Q _p values also indicate that the region is partially saturated with fluids.  相似文献   

An assessment of regional vulnerability of rice to climate change in India   总被引：1，自引：0，他引：1  

Naresh Kumar Soora  P. K. Aggarwal  Rani Saxena  Swaroopa Rani  Surabhi Jain  Nitin Chauhan 《Climatic change》2013,118(3-4):683-699

A simulation analysis was carried out using the InfoCrop-rice model to quantify impacts and adaptation gains, as well as to identify vulnerable regions for irrigated and rain fed rice cultivation in future climates in India. Climates in A1b, A2, B1 and B2 emission scenarios as per a global climate model (MIROC3.2.HI) and a regional climate model (PRECIS) were considered for the study. On an aggregated scale, the mean of all emission scenarios indicate that climate change is likely to reduce irrigated rice yields by ~4 % in 2020 (2010–2039), ~7 % in 2050 (2040–2069), and by ~10 % in 2080 (2070–2099) climate scenarios. On the other hand, rainfed rice yields in India are likely to be reduced by ~6 % in the 2020 scenario, but in the 2050 and 2080 scenarios they are projected to decrease only marginally (<2.5 %). However, spatial variations exist for the magnitude of the impact, with some regions likely to be affected more than others. Adaptation strategies comprising agronomical management can offset negative impacts in the near future—particularly in rainfed conditions—but in the longer run, developing suitable varieties coupled with improved and efficient crop husbandry will become essential. For irrigated rice crop, genotypic and agronomic improvements will become crucial; while for rainfed conditions, improved management and additional fertilizers will be needed. Basically climate change is likely to exhibit three types of impacts on rice crop: i) regions that are adversely affected by climate change can gain in net productivity with adaptation; ii) regions that are adversely affected will still remain vulnerable despite adaptation gains; and iii) rainfed regions (with currently low rainfall) that are likely to gain due to increase in rainfall can further benefit by adaptation. Regions falling in the vulnerable category even after suggested adaptation to climate change will require more intensive, specific and innovative adaptation options. The present analysis indicates the possibility of substantial improvement in yields with efficient utilization of inputs and adoption of improved varieties.  相似文献   

Rapid Determination of Trace and Ultra Trace Level Elements in Diverse Silicate Rocks in Pressed Powder Pellet Targets by LA‐ICP‐MS using a Matrix‐Independent Protocol     

Pulok K. Mukherjee  Param P. Khanna  Naresh K. Saini 《Geostandards and Geoanalytical Research》2014,38(3):363-379

A simple, single sample preparation involving pressed rock powder pellets was utilised to determine the trace and ultra trace abundances of petrogenetically important elements including high field‐strength elements and REEs by laser ablation‐ICP‐MS. One of the elements predetermined by XRF spectrometry served as an internal standard. The influence of sample preparation parameters (grain size, pellet compactness and amount of binding media) on analytical performance was also investigated, including sample homogeneity issues at the laser sampling scale. Line scanning with a high repetition frequency (20 Hz) and large beam diameter (200 μm) ensured ablation from a larger sample surface area, eliminating issues related to sample heterogeneity. A median grain size of about 10 μm for silicate rock powders was found to be sufficiently representative at this scale of laser sampling. Granitic rocks or samples containing resistant minerals such as zircon needed extra grinding to achieve grain sizes down to < 5 μm for better precision for elements that are concentrated in these phases. Using ¹³⁷Ba as an internal standard, reasonable accuracies within 15–20% for most of the high mass trace elements were achieved; in the case of low mass elements, it may deviate up to 40%. Precision of measurements rarely exceeded 15% RSD.  相似文献   

Preparation and Characterisation of Two Geochemical Reference Materials: DG‐H (Granite) and AM‐H (Amphibolite) from the Himalayan Orogenic Belt     

Naresh K. Saini  Param P. Khanna  Pulok K. Mukherjee  Kishor K. Purohit 《Geostandards and Geoanalytical Research》2014,38(1):111-122

Two geochemical reference materials of Himalayan origin named DG‐H (a granite) and AM‐H (an amphibolite) prepared by the Wadia Institute of Himalayan Geology Dehradun are described. Both samples were collected from the NW Himachal Himalaya in India. With the participation of analysts from more than forty international laboratories, element determination data collected during the past 10 years for characterisation of the samples was processed to assign working values using statistical procedures in use for this purpose. Earlier work published on these samples is incorporated in the present communication making it an updated document. The typical chemical and petrological characteristics of these two samples may prove useful for method validation and calibration of analytical instruments used for analysing similar rock types, and for widening the analytical range of several analytical methods used for geochemical analysis.  相似文献   

Variable anelastic attenuation and site effect in estimating source parameters of various major earthquakes including M w 7.8 Nepal and M w 7.5 Hindu kush earthquake by using far-field strong-motion data     

Kumar  Naresh  Kumar  Parveen  Chauhan  Vishal  Hazarika  Devajit 《International Journal of Earth Sciences》2017,106(7):2371-2386

International Journal of Earth Sciences - Strong-motion records of recent Gorkha Nepal earthquake (M w 7.8), its strong aftershocks and seismic events of Hindu kush region have been analysed for...  相似文献   

Evaluating the impact of climate change in threshold values of thermodynamic indices during pre-monsoon thunderstorm season over Eastern India     

Sahu  Rajesh Kumar  Dadich  Jiteshwar  Tyagi  Bhishma  Vissa  Naresh Krishna  Singh  Jyotsna 《Natural Hazards》2020,102(3):1541-1569

Natural Hazards - The present study analyses thermodynamic indices variation over three sites of eastern Indian region: Bhubaneswar, Kolkata and Ranchi, associated with pre-monsoon thunderstorms...  相似文献