Effect of Corrugation and Reinforcement on the Dispersion of SH-wave Propagation in Corrugated Poroelastic Layer Lying over a Fibre-reinforced Half-space   总被引：1，自引：1，他引：0  

Abhishek Kumar Singh  Amrita Das  Anirban Lakshman  Amares Chattopadhyay 《Acta Geophysica》2016,64(5):1340-1369

The presence of porosity and reinforcement in a medium is an important factor affecting seismic wave propagation and plays vital role in many geophysical prospects. Also, the presence of salt and ore deposits, mountains, basins, mountain roots, etc. is responsible for the existence of corrugated boundary surfaces of constituent layers. Such facts brought motivation for the present paper which deals with the propagation of SH-wave in a heterogeneous fluid-saturated poroelastic layer with corrugated boundaries lying over an initially stressed fibre-reinforced elastic halfspace. Closed form of dispersion relation has been obtained and is found in well agreement to classical Love wave equation for isotropic case. The effect of corrugation, wave number, undulation, position parameter, horizontal compressive/tensile initial stress and heterogeneity on phase velocity has been analysed through numerical computation and graphical illustration. Moreover, comparative study exploring the effect of presence and absence of reinforcement in half-space on dispersion curve is the major highlight of the current study.  相似文献   

Lithosphere of the Dharwar craton by joint inversion of P and S receiver functions   总被引：1，自引：0，他引：1  

S. Kiselev  L. Vinnik  S. Oreshin  S. Gupta  S. S. Rai  A. Singh  M. R. Kumar  G. Mohan 《Geophysical Journal International》2008,173(3):1106-1118

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Evolution of primordial black holes in Jordan–Brans–Dicke cosmology     

A. S. Majumdar  D. Gangopadhyay  L. P. Singh 《Monthly notices of the Royal Astronomical Society》2008,385(3):1467-1470

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Recent Sea Level and Sea Surface Temperature Changes Along the Maldives Coast     

O. P. Singh  Tariq Masood Ali Khan  Fahmida Aktar  Majajul Alam Sarker 《Marine Geodesy》2013,36(4):209-218

Maldives, a South Asian small island nation in the northern part of the Indian Ocean is extremely vulnerable to the impacts of Sea Level Rise (SLR) due to its low altitude from the mean sea level. This artricle attempts to estimate the recent rates of SLR in Maldives during different seasons of the year with the help of existing tidal data recorded in the Maldives coast. Corresponding Sea Surface Temperature (SST) trends, utilizing reliable satellite climatology, have also been obtained. The relationships between the SST and mean sea level have been comprehensively investigated. Results show that recent sea level trends in the Maldives coast are very high. At Male, the capital of the Republic of Maldives, the rising rates of Mean Tidal Level (MTL) are: 8.5, 7.6, and 5.8 mm/year during the postmonsoon (October-December), Premonsoon (March-May) and southwest monsoon (June-September) seasons respectively. At Gan, a station very close to the equator, the increasing rate of MTL is maximum during the period from June to September (which is 6.2 mm/year). These rising trends in MTL along the Maldives coast are certainly alarming for this small developing island nation, which is hardly one meter above the mean sea level. Thus there is a need for careful monitoring of future sea level changes in the Maldives coast. The trends presented are based on the available time-series of MTL for the Maldives coast, which are rather short. These trends need not necessarily reflect the long-term scenario. SST in the Maldives coast has also registered significant increasing trend during the period from June to September. There are large seasonal variations in the SST trends at Gan but SST and MTL trends at Male are consistently increasing during all the seasons and the rising rates are very high. The interannual mode of variation is prominent both in SST as well as MTL. Annual profile of MTL along the Maldives coast is bimodal, having two maxima during April and July. The April Mode is by far the dominant one. The SST appears to be the main factor governing the sea level variations along the Maldives coast. The influence of SST and sea level is more near the equatorial region (i.e., at Gan). There is lag of about two months for the maximum influence of SST on the sea level. The correlation coefficient between the smoothed SST and mean tidal level at Gan with lag of two months is as high as ~ +0.8, which is highly significant. The corresponding correlation coefficients at Male with the lags of one and two months are +0.5 and +0.3, respectively. Thus, the important finding of the present work for the Maldives coast is the dominance of SST factor in sea level variation, especially near the region close to the equator.  相似文献   

Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon   总被引：1，自引：1，他引：0  

O. P. Singh Tariq Masood Ali Khan  Tad S. Murty  Md. Sazedur Rahman 《Marine Geodesy》2013,36(1):65-72

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.  相似文献   

A parsimonious crop-water productivity index: an application to Brazil     

Marco P Maneta  Purnendu N Singh  Marcelo Torres  Wesley W Wallender  Stephen A Vosti  Lineu N Rodrigues  Luis H Bassoi  Julie A Young 《Area》2009,41(1):94-106

Reducing poverty in rural areas of developing countries requires sustained and sustainable increases in agricultural water productivity. However, aside from traditional measures of precipitation, little is known about water available to farmers or how productively they use it. We present a crop-water productivity index (a ratio of the value of annual crop production to a dimensionless potential water availability index) for large water basins using readily available low-resolution data. The index is transferable, permits direct inter-basin comparisons, and is simple to calculate. We calculate the index for each municipality in the São Francisco river basin in Brazil. No clear patterns linking water availability and value of agricultural output are evident, even though clusters of municípios with high- and low-crop-water productivity emerge, and the former may be useful in guiding policies aimed at increasing water productivity. Finally, analyses of the effects of information uncertainty on the crop-water productivity index suggest that the returns to agricultural investments in certain places in the São Francisco river basin are more risky than others. Improvements in data quality and quantity can help refine estimates of the index and reduce their uncertainty.  相似文献   

Hisslers observed during daytime in a low latitude ground station     

Krishna Kumar Singh  Ravindra Pratap Patel  Balraj Kumar  Mohamad Altaf  Prince Ahmad Ganai  Abhay Kumar Singh  Ram Pal Singh  Lalmani 《Acta Geophysica》2009,57(2):536-547

The observation of hisslers during daytime at low latitude station Jammu, India, is reported. The hissler elements are quasi-periodic falling tones observed during the period of hiss activity and appear in minutelong sequences with average spacing between individual elements of the order of 0.15 s. Hissler elements exhibit almost no dispersion and no complex internal structure in slope and intensity, and successive hissler elements do not overlap in time. It seems that the reported hisslers might have propagated in prolongitudinal mode.  相似文献   

Trace metals in antifouling paint particles and their heterogeneous contamination of coastal sediments   总被引：4，自引：0，他引：4  

Nimisha Singh 《Marine pollution bulletin》2009,58(4):559-564

Antifouling paint residues collected from the hard-standings of a marine leisure boat facility have been chemically characterised. Scanning electron microscopy revealed distinct layers, many containing oxidic particles of Cu and Zn. Quantitative analysis indicated concentrations of Cu and Zn averaging about 300 and 100 mg g⁻¹, respectively, and small proportions of these metals (<2%) in organometallic form as pyrithione compounds. Other trace metals present included Ag, Cd, Cr, Ni, Pb and Sn, with maximum concentrations of about 330, 75, 1200, 780, 1800 and 25,000 μg g⁻¹, respectively. Estuarine sediment collected near a boatyard contained concentrations of Cu and Zn an order of magnitude greater than respective concentrations in “background” sediment, and mass balance calculations suggested that the former sample was contaminated by about 1% by weight of paint particles. Clearly, antifouling residues represent a highly significant, heterogeneous source of metallic contamination in the marine environment where boating activities occur.  相似文献   

Deterministic Seismic Scenarios for Imphal City     

S. T. G. Raghu Kanth  Konjengbam Darunkumar Singh  Kumar Pallav 《Pure and Applied Geophysics》2009,166(4):641-672

In this article, the spatial variation of ground motion in Imphal City has been estimated by the finite-fault seismological model coupled with site response analysis. The important seismic sources around Imphal City have been identified from the fault map and past seismicity data. The rock level acceleration time histories at Imphal City for the 1869 Cachar (M_w 7.5) earthquake and a hypothetical M_w 8.1 event in the Indo-Burma subduction zone have been estimated by a stochastic finite-fault model. Soil investigation data of 122 boreholes have been collected from several construction projects in Imphal City. Site response analysis has been carried out and the surface level ground motion has been determined for Imphal City for these two earthquake events. The results are presented in the form of peak ground acceleration (PGA) contour map. From the present study it has been ascertained that the maximum amplification for PGA over Imphal City is as high as 2.5. The obtained contour maps can serve as guidelines for identifying vulnerable areas and disaster mitigation in Imphal City.  相似文献   

Low frequency drought variability associated with climate indices     

Mehmet Özger  Ashok K. Mishra  Vijay P. Singh 《Journal of Hydrology》2009,364(1-2):152-162

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