Spatial variation and conditional simulation of seismic ground motion     

Gopala Krishna Rodda  Dhiman Basu 《Bulletin of Earthquake Engineering》2018,16(10):4399-4426

Spatially varying ground motion (SVGM) may have influence on certain civil engineering structures with spatially extended superstructure and/or substructures. Conditional simulation of spatially varying ground motion (CSSVGM) may be viewed from two different perspectives. Most procedures available in the literature neglect the spatial variability in auto-spectral density (ASD) and estimate the SVGM through cross-spectral density (CSD) which was computed using the empirical coherency models. This paper proposes a coherency model that accounts for the spatial variability of ASD. A framework has been developed for the CSSVGM, through the mapping of both proposed coherency model and ASD over the footprint of an array. Current framework (existing in the literature) accounts for only the phase variability of SVGM while proposed framework accounts for both phase and amplitude variability. Ground motion generated from both perspectives is then assessed with the data recorded over SMART1 and LSST arrays. For the purpose of assessment, a definition of target spectrum based on the direction of arrival is explored. The effect of choice of coherency model on the simulated spatially varying ground motion is investigated first. Spectra resulting from both the perspectives are assessed against the target spectrum. An attempt has been made to predict the SVGM for a future event using a coherency model calibrated against a past event and an estimate of ASD of the seed ground motion. Finally, the effect of form of ASD (of a seed ground motion) on SVGM simulated is investigated by considering the ASD in different forms. Simulating SVGM through the mapping of both coherency model and ASD seems to be more appropriate than through CSD.  相似文献   

RS & GIS-based landslide susceptibility mapping of the Balason River basin,Darjeeling Himalaya,using logistic regression (LR) model     

Subrata Mondal  Sujit Mandal 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(1):29-44

The present study deals with the preparation of a landslide susceptibility map of the Balason River basin, Darjeeling Himalaya, using a logistic regression model based on Geographic Information System and Remote Sensing. The landslide inventory map was prepared with a total of 295 landslide locations extracted from various satellite images and intensive field survey. Topographical maps, satellite images, geological, geomorphological, soil, rainfall and seismic data were collected, processed and constructed into a spatial database in a GIS environment. The chosen landslide-conditioning factors were altitude, slope aspect, slope angle, slope curvature, geology, geomorphology, soil, land use/land cover, normalised differential vegetation index, drainage density, lineament number density, distance from lineament, distance to drainage, stream power index, topographic wetted index, rainfall and peak ground acceleration. The produced landslide susceptibility map satisfied the decision rules and ?2 Log likelihood, Cox &; Snell R-Square and Nagelkerke R-Square values proved that all the independent variables were statistically significant. The receiver operating characteristic curve showed that the prediction accuracy of the landslide probability map was 96.10%. The proposed LR method can be used in other hazard/disaster studies and decision-making.  相似文献   

A numerical method for the solution of the nonlinear turbulent one-dimensional free surface flow equations     

Sujit K Bose 《Computational Geosciences》2018,22(1):81-86

Free surface flow of an incompressible fluid over a shallow plane/undulating horizontal bed is characteristically turbulent due to disturbances generated by the bed resistance and other causes. The governing equations of such flows in one dimension, for finite amplitude of surface elevation over the bed, are the Continuity Equation and a highly nonlinear Momentum Equation of order three. The method developed in this paper introduces the “discharge” variable q = η U, where η = elevation of the free surface above the bed level, and U = average stream-wise forward velocity. By this substitution, the continuity equation becomes a linear first-order PDE and the momentum equation is transformed after introduction of a small approximation in the fifth term. Next, it is shown by an invertibility argument that q can be a function of η: q = F(η), rendering the momentum equation as a first order, second degree ODE for F(η), that can be be integrated by the Runge-Kutta method. The continuity equation then takes the form of a first order evolutionary PDE that can be integrated by a Lax-Wendroff type of scheme for the temporal evolution of the surface elevation η. The method is implemented for two particular cases: when the initial elevation is triangular with vertical angle of 120 ^° and when it has a sinusoidal form. The computations exhibit the physically interesting feature that the frontal portion of the propagating wave undergoes a sharp jump followed by tumbling over as a breaker. Compared to other discretization methods, the application of the Runge-Kutta and an extended version of the Lax-Wendroff scheme is much easier.  相似文献   

Estimation of Raft Settlement Based on Linear Elastic Finite Element Analysis     

Bhartiya  Priyanka  Chakraborty  Tanusree  Basu  Dipanjan 《Geotechnical and Geological Engineering》2022,40(6):2907-2919

Geotechnical and Geological Engineering - A detailed parametric study based on linear-elastic three-dimensional finite element (FE) analysis with proper raft–soil interaction is performed for...  相似文献   

Laboratory Thermal Performance Tests on a Model Heat Exchanger Pile in Sand     

Cory A. Kramer  Omid Ghasemi-Fare  Prasenjit Basu 《Geotechnical and Geological Engineering》2015,33(2):253-271

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Seismic clusters and their characteristics at the Arabian Sea Triple Junction: Supportive evidences for plate margin deformations     

Basab Mukhopadhyay  Manoj Mukhopadhyay  Sujit Dasgupta 《Journal of the Geological Society of India》2011,78(2):131-146

The plate margin features defining the Arabian Sea Triple Junction (ASTJ) are: the Aden Ridge (AR), Sheba Ridge (SR) with their intervening Alula-Fartak Transform (AFT), Carlsberg Ridge (CR) and Owen Fracture Zone (OFZ). Exact nature of ASTJ is presently debated: whether it is RRF (ridge-ridge-fault) or RRR (ridge-ridge-ridge) type. A revised seismicity map for ASTJ is given here using data for a period little more than a century. “Point density spatial statistical criterion” is applied to short-listed 742 earthquakes (mb ≥ 4.3), 10 numbers of spatio-temporal seismic clusters are identified for ASTJ and its arms. Relocated hypocentres help better constraining the cluster identification wherever such data exist. Seismic clusters actually diagnose the most intense zones of strain accumulation due to far field as well as the local stress operating at ASTJ. An earthquake swarm emanating from a prominent seismic cluster below SR provides an opportunity to investigate the pore pressure diffusion process (due to the active source) by means of “r-t plot”. Stress and faulting pattern in the active zones are deduced from 43 CMT solutions. While normal or lateral faulting is characteristic for these arms, an anomalous thrust earthquake occurs in the triangular ‘Wheatley Deep’ deformation zone proximal to ASTJ. The latter appears to have formed due to a shift of the deformational front from OFZ towards a transform that offsets SR. Though ASTJ is still in the process of evolution, available data favour that this RRF triple junction may eventually be converted to a more stable RRR type.  相似文献   

New technologies, old divides: linking internet access to social and locational characteristics of US farms     

Pratyusha Basu  Jayajit Chakraborty 《GeoJournal》2011,76(5):469-481

Access to new information and communication technologies is widely viewed as a prerequisite for participation in the global economy, so that inequalities in such access have become a significant policy concern. Rural areas are especially underserved in terms of internet providers, and this is true in both developed and less developed economies. This article focuses on access to the internet within farming operations in the US as an important aspect of understanding the digital divide within rural areas. Using county level data from the 2007 US Census of Agriculture and multivariate regression analysis, our study examines the statistical relationship between farm internet access and a set of explanatory factors which include demographic characteristics of operators, economic characteristics of farms, and geographic location (region and metropolitan status) of the farm. Further, it seeks to understand whether access to the internet can be socially and locationally differentiated from access to high speed internet. Our findings indicate that existing social divides are replicated in terms of the digital divide, so that social inequalities are potentially a more pressing problem than infrastructural gaps in terms of rural access to the internet in the US.  相似文献   

Effects of bedrock anisotropy on hillslope failure in the Darjeeling-Sikkim Himalaya: an insight from physical and numerical models     

Sujit Roy  Amiya Baruah  Santanu Misra  Nibir Mandal 《Landslides》2015,12(5):927-941

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Precambrian crustal growth and tectonics: introduction     

Vinod K. Singh  Ram Chandra  Asish R. Basu  Surendra P. Verma  Tapas K. Biswal 《International Geology Review》2015,57(11-12):v-viii

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Mapping optical ray trajectories through island wake vortices     

Christopher G. Nunalee  Ping He  Sukanta Basu  Jean Minet  Mikhail A. Vorontsov 《Meteorology and Atmospheric Physics》2015,127(3):355-368

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