Response of multiply supported secondary systems to earthquakes in frequency domain     

Aparna Dey  Vinay K. Gupta 《地震工程与结构动力学》1998,27(2):187-201

A new formulation of the transfer function has been proposed for the seismic analysis of linear, multiply supported secondary systems. The transfer function for a given response quantity has been formulated by directly using the fixed-base modes of the primary and secondary systems. This approach is exact and does not involve the determination of the combined system properties. Further, it is applicable to the secondary systems with various mass ratios and configurations. A few example primary–secondary systems have been considered to illustrate the proposed formulation in case of different mass ratios. It has also been shown how the proposed formulation can be used to obtain reasonably accurate stochastic estimates of the secondary system responses. © 1998 John Wiley & Sons, Ltd.  相似文献   

A time-domain nonlinear effective-stress non-Masing approach of ground response analysis of Guwahati city,India     

Basu  Devdeep  Boga  Madhulatha  Dey  Arindam 《地震工程与工程振动(英文版)》2019,18(1):61-75

The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.  相似文献   

TeV neutrinos and gamma-rays from pulsars     

A. Bhadra  R. K. Dey 《Monthly notices of the Royal Astronomical Society》2009,395(3):1371-1375

Recent studies suggest that pulsars could be strong sources of TeV muon neutrinos provided positive ions are accelerated by pulsar polar caps to PeV energies. In such a situation, muon neutrinos are produced through the Δ-resonance in interactions of pulsar-accelerated ions with its thermal radiation field. High-energy gamma-rays should also be produced simultaneously in pulsar environment as both charged and neutral pions are generated in the interactions of energetic hadrons with the ambient photon fields. Here, we estimate TeV gamma-ray flux at the Earth from a few nearby young pulsars. When compared with the observations, we find that proper consideration of the effect of polar cap geometry in flux calculation is important. Incorporating such an effect, we obtain the (revised) event rates at the Earth due to a few potential nearby pulsars. The results suggest that pulsars are unlikely to be detected by the upcoming neutrino telescopes. We also estimate TeV gamma-ray and neutrino fluxes from pulsar nebulae for the adopted model of particle acceleration.  相似文献   

Nagaur — tertiary interface under Punjab-Haryana semi-desertic plains in western India     

R. C. Dey 《Journal of the Geological Society of India》2009,74(1):131-137

The subsurface Nagaur Basin in northwest Haryana and southwest Punjab hosts evaporite sequence, conformably overlain by Nagaur red beds and grey beds. A polymictic conglomerate intervenes the Nagaur sequence and the overlying Tertiary sequence. The focus is on the new finds of (i) distinctive ‘grey beds’ overlying ubiquitous red beds, (ii) ‘Malout conglomerate and grit’ horizon (Palaeocene-Miocene) marking an unconformity over the Nagaur Group (early Cambrian) and (iii) ‘entrapped gas and dried-up leaves/carbonaceous flakes’ in the conglomerate unit and succeeding Tertiary rocks. Palaeoenvironmental significance has been discussed. The Nagaur ‘red beds’ has been likened to ‘continental red beds’ of Schreiber (1978) and ‘reworked red beds’ of Krynine (1949). The ‘grey beds’ are channel fillings, fresh material having been derived from fresh cuttings by streams/rivers following structural grains in the Aravalli landscape where the interfluves provided weathered (oxidised) materials for the red beds. Association of continental red beds and grey beds is known in the Newark Series (Triassic) of the Eastern United States and the Keweenawan ‘late Precambrian’ of the Lake Superior region.  相似文献   

Morphological signatures of fault lines in an earthquake prone zone of southern Baromura hill,north-east India: a multi sources approach for spatial data analysis   总被引：3，自引：2，他引：1  

Sudip Dey  Prasamita Sarkar  Chandrani Debbarma 《Environmental Earth Sciences》2009,59(2):353-361

This paper aims to assess the morphological signatures of tectonic features (faults) on the basis of multi sources spatial data analysis. For that purpose, the present authors selected the southern part of Baromura hill of Tripura, which has been discussed very little in the scientific literatures. An extensive field work was done in the assumed faulted areas to understand the geomorphic signatures of faulting. In the field, GPS was used for fixing the ground control points. Scanned Survey of India (SOI) topographical sheets, SPOT PAN and Land sat band-5 was used for digital analysis. An old DEM on IRS LISS-III FCC was also consulted for final mapping. Two clear lineaments (Faults) were detected from field observation on southern Baromura hill. Apart from these, another one was found in the outer part of this hill range. An attempt was made to explain the morphological signatures of those faults by density slicing on radiometric data based on emittance of different physical components. Finally a geomorphic map with main tectonic features of Baromura was prepared for future disaster management planning.  相似文献   

Review of Cuttability Indices and A New Rockmass Classification Approach for Selection of Surface Miners     

Kaushik Dey  A. K. Ghose 《Rock Mechanics and Rock Engineering》2011,44(5):601-611

Rock excavation is carried out either by drilling and blasting or using rock-cutting machines like rippers, bucket wheel excavators, surface miners, road headers etc. Economics of mechanised rock excavation by rock-cutting machines largely depends on the achieved production rates. Thus, assessment of the performance (productivity) is important prior to deploying a rock-cutting machine. In doing so, several researchers have classified rockmass in different ways and have developed cuttability indices to correlate machine performance directly. However, most of these indices were developed to assess the performance of road headers/tunnel-boring machines apart from a few that were developed in the earlier days when the ripper was a popular excavating equipment. Presently, around 400 surface miners are in operation around the world amongst which, 105 are in India. Until now, no rockmass classification system is available to assess the performance of surface miners. Surface miners are being deployed largely on trial and error basis or based on the performance charts provided by the manufacturer. In this context, it is logical to establish a suitable cuttability index to predict the performance of surface miners. In this present paper, the existing cuttability indices are reviewed and a new cuttability indexes proposed. A new relationship is also developed to predict the output from surface miners using the proposed cuttability index.  相似文献   

Variations In Upper Mantle Structure Under Northern Australia     

S. C. Dey  B. L. N. Kennett  J. R. Bowman  A. Goody 《Geophysical Journal International》1993,114(2):304-310

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Wide-angle linear forward modelling of synthetic seismograms     

A. Dey  A. Gisolf 《Geophysical Prospecting》2007,55(5):707-718

We address the issue of linearity and scale dependence in forward modelling of seismic data from well logs, for large ray parameters, wide angles or large offsets. We present a forward model, within the context of seismic‐to‐well matching, that is linearized in the elastic properties of the earth. This model preserves linearity at large ray parameters and can handle fine‐layering effects such as induced anisotropy. Starting from a low‐contrast small‐ray‐parameter model, we extend it to a large‐ray‐parameter model by fully linearizing the elastic‐property contrasts. Overall linearity of the forward model is extended by partitioning the compressional‐wave and shear‐wave velocity fields into two fundamental scales: a kinematic scale that governs wavefield propagation effects and a dynamic scale that governs wavefield scattering effects. This analysis reveals that the standard practice in forward modelling of strongly filtering the ratio of compressional‐wave velocity to shear‐wave velocity is well founded in the underlying physics. The partitioning of the velocity fields also leads naturally to forward modelling that accounts fully for stretch effects, to resolution of the angle‐of‐incidence versus ray‐parameter dichotomy in seismic‐amplitude analysis, and to full accounting for induced anisotropy and dispersion effects due to fine‐layering of isotropic media. With the onset of routine long‐offset acquisition and the compelling need to optimize asset management in order to maximize reserve recovery, this forward model recognizes the physics of seismic wave propagation and enables a more complete exploitation of amplitude information in pre‐critical seismic data.  相似文献   

Seismic induced soil gas radon anomalies observed at multiparametric geophysical observatory,Tezpur (Eastern Himalaya), India: an appraisal of probable model for earthquake forecasting based on peak of radon anomalies     

Chetia  Timangshu  Baruah  Saurabh  Dey  Chandan  Baruah  Santanu  Sharma  Sangeeta 《Natural Hazards》2022,111(3):3071-3098

Natural Hazards - We applied multiple linear regressions to scrutinize the maximum variability produced in soil gas radon (Rn-222) by pressure, temperature and rainfall. Statistical methodologies...  相似文献   

Vibroseis deconvolution: a comparison of cross-correlation and frequency-domain sweep deconvolution   总被引：3，自引：0，他引：3  

K.F. Brittle  L.R. Lines  A.K. Dey 《Geophysical Prospecting》2001,49(6):675-686

Ideally, traditional vibroseis processing produces a band-limited zero-phase Klauder wavelet through cross-correlation of the sweep with the recorded signal. An alternative wavelet processing method involves deconvolving the sweep from the recorded vibroseis trace. This deconvolution can be achieved through frequency-domain division. We compare and contrast the advantages and disadvantages of sweep deconvolution versus cross-correlation on synthetic and real data.  相似文献