Effect of surface wave inversion non-uniqueness on 1D seismic ground response analysis     

Narayan Roy  Ravi SankarJakka  H. R. Wason 《Natural Hazards》2013,68(2):1141-1153

Surface wave methods are increasingly being used for geotechnical site characterization. The methodology is based on the dispersive characteristic of Rayleigh waves in vertically heterogeneous medium. Experimental dispersion curve is inverted to obtain one-dimensional shear-wave velocity profile by inverse problem solution. Uncertainty associated with this surface wave inversion has drawn much attention. Inverse problem solution can provide different equivalent shear-wave velocity profiles, which may lead to different seismic site response analysis. In this study, a neighborhood algorithm has been used for inversion of dispersion curve to get a set of equivalent shear-wave velocity profiles. These equivalent velocity profiles are then used for 1D ground response analysis for different input motion record of the same earthquake at different epicentral distances. Results show significant variation in amplification spectrum in terms of maximum amplification as well as peak frequency. The extent of this uncertainty largely depends on the characteristics of the ground motion records at different epicentral distances. A linear variation is observed between mean coefficients of variation of amplification spectrum and epicentral distance of ground motion records. A gradual increase in mean value of peak frequency and peak amplification with the epicentral distance is also observed.  相似文献   

Diversity and Distribution of Microzooplankton Tintinnid (Ciliata: Protozoa) in the Core Region of Indian Sundarban Wetland          下载免费PDF全文

Dibyendu Rakshit  Santosh K. Sarkar  Kamala K. Satpathy  Palani Sankar Ganesh  Nallamuthu Godhantaraman  Jayanta K. Biswas 《洁净——土壤、空气、水》2016,44(10):1278-1286

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Unbiased estimates of galaxy scaling relations from photometric redshift surveys     

Graziano Rossi  Ravi K. Sheth 《Monthly notices of the Royal Astronomical Society》2008,387(2):735-740

Many physical properties of galaxies correlate with one another, and these correlations are often used to constrain galaxy formation models. Such correlations include the colour–magnitude relation, the luminosity–size relation, the fundamental plane, etc. However, the transformation from observable (e.g. angular size, apparent brightness) to physical quantity (physical size, luminosity) is often distance dependent. Noise in the distance estimate will lead to biased estimates of these correlations, thus compromising the ability of photometric redshift surveys to constrain galaxy formation models. We describe two methods which can remove this bias. One is a generalization of the V _max method, and the other is a maximum-likelihood approach. We illustrate their effectiveness by studying the size–luminosity relation in a mock catalogue, although both methods can be applied to other scaling relations as well. We show that if one simply uses photometric redshifts one obtains a biased relation; our methods correct for this bias and recover the true relation.  相似文献   

Vertical uplift capacity of a group of shallow circular plate anchors in sand     

R. Ganesh 《Marine Georesources & Geotechnology》2013,31(3):282-290

ABSTRACT

The uplift capacity of a group of circular plate anchors buried horizontally in sand along a line has been determined. The uplift capacity of an interfering anchor is presented in terms of nondimensional uplift factors, F_γi and F_qi, due to components of soil unit weight and surcharge pressure acting on the ground surface, respectively. Theoretical solutions have been developed by applying the upper bound theorem of limit analysis based on a simple rigid wedge collapse mechanism. In the case of two and infinite number of anchors, closed-form solutions have been developed for computing the factor F_qi, whereas the factor F_γi is determined using a semianalytical approach. As expected, the interference of the anchors leads to a continuous reduction in the uplift resistance with a decrease in the spacing between the anchors, and the uplift resistance decreases with the increasing number of anchors at a given spacing. The results compare reasonably well with the available theoretical and experimental data from the literature.  相似文献   

The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events   总被引：1，自引：0，他引：1  

D.V. Reddy  P. Nagabhushanam  Devender Kumar  B.S. Sukhija  P.J. Thomas  Anand K. Pandey  R.N. Sahoo  G.V. Ravi Prasad  K. Datta 《Tectonophysics》2009,474(3-4):463-472

Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon (¹⁴C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. ¹⁴C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by ¹⁴C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, ¹⁴C dating could constrain the 1548 AD event though not distinctly. Further studies using combined ¹⁴C and OSL dating may better constrain the seismo-chronology of the study region.  相似文献   

Mathematical analysis of a chaotic model in relevance to monsoon ISO     

Sandipan Mukherjee  Ravi Prakash Shukla  Ashok Kumar Mittal  Avinash Chandra Pandey 《Meteorology and Atmospheric Physics》2011,114(3-4):83-93

Mathematical analysis of a predominantly bimodal chaotic attractor, Lu system, was carried out to investigate a possible application of the model as a prototype of monsoon intra-seasonal oscillation (ISO). Bifurcation structures of the system are explored as the system parameter c and the forcing parameter F are varied. Stability criteria of equilibrium points of the forced Lu system are also explored in detail. A sensitivity study is carried out, by changing forcing parameter F, to explore relationships between some of the derived variables of the model and, based on such relationships, an empirical rule is used for extended range prediction. Analogous variables are also derived from the ISO data and prediction results are compared. Application of the prediction rule of regime transition to the observed ISO and chaotic model data is purely based on the bimodal characteristics of ISO and neglects some of the intricate mechanisms therein. We have found that a forced Lu system can be a good prototype in the prediction of peak anomaly of the monsoon ISO when growth rates around a threshold value are taken as predictors.  相似文献   

Hill slope stability analysis using two and three dimensions analysis: A comparative study     

Rajesh Singh  Ravi Kumar Umrao  T. N. Singh 《Journal of the Geological Society of India》2017,89(3):295-302

Slope instability is very common phenomenon, especially in tectonically active hills of the lesser Himalaya. The deformed, weathered and fragile rocks of the lesser Himalaya are often vulnerable under natural or anthropogenic influences. There were several cases of slope failure along highway sections in Uttarakhand Himalaya. The study was carried out along a highway section of NH-109. The factor of safety (FoS) is commonly most acceptable parameter that analyses the health of slopes. The two dimensional (2D) numerical analysis techniques are commonly used to obtain the FoS. It is observed that many times FoS obtained from 2D analysis techniques do not qualify the actual conditions and are usually lower in value as compared to ground conditions. This, in turn, increases the cost of remedial measures used for protection of slopes. This paper presents a comparative study of 2D and 3D numerical analysis based on the finite difference method (FDM) using fast Langrangian analysis of continua (FLAC) codes. The study indicates that there is no appreciable difference between FoS values obtained from 2D and 3D analysis based on the selected slope conditions. The difference ranges from 0.02 to 0.07 for analysed cases in uniform rock mass. The study also exhibits some of the important analytical observations and effects of variables on resultant FoS.  相似文献   

Interpretation of coastal wind transfer functions with momentum balances derived from idealized numerical model simulations     

Sung Yong Kim  Ganesh Gopalakrishnan  Aurelien Ponte 《Ocean Dynamics》2015,65(1):115-141

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Effectiveness of Dichanthium annulatum in Watercourses for Reducing Sediment Delivery from Agricultural Watersheds          下载免费PDF全文

Battu Krishna Rao  Prasanta K. Mishra  Ravi S. Kurothe  Vinod C. Pande  Gopal Kumar 《洁净——土壤、空气、水》2015,43(5):710-716

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Phodong (Sikkim) earthquake of 14 February 2006 and its aftershocks—Coulomb stress analysis     

P. Solomon Raju  V.K. Gahalaut  M. Ravi Kumar 《Journal of Geodynamics》2008,46(1-2):63-67

The 14 February 2006 Phodong (Sikkim) earthquake of moderate magnitude (Mw 5.3) triggered several aftershocks that were recorded by a local seismic network. The thrust earthquake is part of the continuing earthquake activity in the Himalayan seismic belt region that occurs on the detachment or ramp under the Higher Himalaya. The aftershocks of the earthquake occurred in increased stress regions caused by the earthquake rupture. Triggering of aftershocks by such a moderate magnitude earthquake implies that the faults in the Himalaya are critically stressed and even a small change of stress, about 0.001–0.002 MPa, can trigger earthquakes on such faults.  相似文献