Raghukanth Stg

Indian Institute of Technology Madras | IIT Madras · Department of Civil Engineering

Ground motion prediction equations (GMPEs) are developed using past strong-motion records to predict the effect of future events. Often, the records in the database are incomplete, not covering all possible input scenarios or not recorded at the site of interest for performing site-specific hazards. Such cases are handled by adjusting the GMPEs to...

This article focuses on estimating the seismic recurrence parameters of India and adjoining regions based on a comprehensive catalogue assimilated from various sources. The study region encompasses latitude 0∘ N–40∘ N and longitude 65∘ E–100∘ E. The updated catalogue for the region contained 69519 events, including 28770 mainshocks. The updated cat...

According to the current Indian Standard earthquake-resistant design code (IS 1893, 2016), the vertical design spectrum is assumed as two-thirds of the horizontal spectrum. However, a previous investigation of the Indian ground motion records suggests that the vertical spectra exceeded the horizontal in many instances, which would render the previo...

The present study aims at simulating broadband ground motions in the epicentral region of the 2015 Mw 7.9 Nepal event, using hybrid broadband technique. The spectral element method is used to simulate the low-frequency ground motion. The 3D material property variation and the basin geometry at the Kathmandu basin are incorporated in the spectral el...

This study presents broadband (BB) ground motions for two historical earthquakes (Mw ≥ 8) in Northeast (NE) India. We apply a recently developed geology-based 3D velocity model of the Northeastern region (NER) to simulate low frequency (LF) ground motions (f < 1Hz). These synthetics are further combined with high frequency (HF) scattering wave-fiel...

Developing a ground motion model (GMM) for Fourier amplitude spectrum (FAS) is essential in seismology and engineering for generating response spectrum and synthetic time histories. Despite data-driven techniques being efficient in modeling complex relations, very few GMMs are developed for FAS using them. An efficient hybrid data-driven algorithm...

This paper presents the results of a study on the characteristics of vertical-to-horizontal ratio (V/H) of 5% damped acceleration spectra for Indian ground motion records. Preliminary analysis indicates that at least 50% of the records exceed the Indian seismic design code considered norm of 2/3 at both the short and long period ranges. In addition...

Peak ground motions and spectral accelerations estimated from the prediction equations are highly significant in earthquake hazard studies. Recently, these predictive relationships developed for higher-order parameters obtained paramount importance as they describe different ground motion characteristics. The northeastern region of India experience...

The ground motions recorded in the near‐field regions of earthquakes reveal that, along with translational motions the rotational motions can severely damage structures. To capture these ground rotations more realistically, the present study makes a novel attempt to model the Earth medium as a horizontally layered reduced micropolar half‐space. Lay...

The present paper analyzes the effect of Himalayan topography on ground motion’s characteristics due to a hypothetical earthquake event of high magnitude. A spectral finite element model is developed to incorporate the Himalayan topography and three-dimensional velocity model for the Himalayan region. The developed model is validated by simulating...

The 25 th April 2015 Nepal earthquake is the first major event in the Himalayan orogeny that provides a relatively well recorded dataset. This paper presents a comprehensive analysis of the mainshock and its five major aftershocks through 21 well established ground motion parameters. The analysis is presented for near field stations of the Kathmand...

This study presents broadband ground motions for the Indo-Gangetic basin, a large sedimentary basin in India, for potential future great (Mw 8.5) Himalayan earthquakes. We use a recently developed 3D earth structure model of the basin as an input to simulate low-frequency ground motion (0–0.5 Hz). These ground motions are further combined with high...

The present study aims at developing a prediction model for ground motion intensity measures using the artificial neural network (ANN) technique for active shallow crustal earthquakes in India. The database for the study consists of 659 ground motion records collected from 138 earthquakes recorded by various seismic networks in the study region. Ow...

The present article focusses on determining the response of reduced micropolar half-space subjected to specific loading conditions. Analytical expressions for translational and rotational displacements are derived for the half-space subjected to impulses using the method of potentials. The derived analytical expressions are numerically evaluated to...

In this paper, the utility of power spectral density (PSD) in ground motion prediction for hazard analysis is examined. The main advantage of PSD is that the area under PSD of excitation gives the energy of the excitation and it is structure independent. The PSD of ground motion from past earthquakes and properties of PSD in terms of spectral momen...

Indo-Gangetic (IG) Basin, formed between the Indian shield and Himalayas, is the largest sedimentary basin in India. The region also constitutes many metropolitan cities, including the capital city New Delhi. The seismic risk in the region is attributed due to the proximity to seismically active Himalayan faults, the possible seismic wave amplifica...

As damage is better correlated to displacements than forces during an earthquake, displacement response spectrum (DRS) is critical for important structures. However, there are no past attempts to develop attenuation relations or response spectra for displacement spectral ordinates. Hence, in this study, probabilistic seismic hazard analysis (PSHA)...

The geologic analysis of lunar tectonic and co‐existing mass wasting features provides important insights into seismicity, seismic ground motion, and the seismic risk of the landed missions. Hence, we performed a detailed geologic mapping of tectonic features and co‐seismic boulder avalanches present at the 930‐km‐diameter lunar Orientale basin. We...

The present work aims at developing the first probabilistic fling hazard map of India and adjoined regions. First, we developed a new ANN-based ground motion prediction equation (GMPE) for fling corresponding to horizontal and vertical directions. The developed GMPE is based on permanent ground residual displacement from 556 scenario events conside...

The present work aims to ascertain the deterministic tsunami hazard map for maximum wave height along the Indian coastline due to subduction events in the Sumatra region. The region between 15°S-30°N lat. and 50°E-115°N long. was modelled in using Geoclaw, which discretizes and solves the shallow-water wave equation using adaptive finite volume alg...

This article addresses the effect of the rupture process on tsunami wave simulations by assessing the propagation of uncertainties from source to wave heights. Thirteen slip models available for the 2004 (Mw 9.2) Sumatra earthquake are utilized in the evaluation. First, quasi-static displacement of the ocean floor is estimated using Okada’s solutio...

The present work aims at exploring the application of nonlinear principal component analysis in dimensionality reduction and prediction of response spectra. The evaluation is performed based on log10 scaled response spectra at 91 spectral periods corresponding to 13552 records available in the NGA-West2 database. The non-linear principal component...

The present work aims at building a non-stationary random field model for the slip distribution on the rupture plane. The estimates are arrived based on 230 slip fields available in the SRCMOD database. The evaluation is performed by segregating and quantifying the trend and fluctuation components of the field. Here, the trend portion of the slip i...

This work aims at developing a hybrid ground motion prediction equation (GMPE) for spectral acceleration in Western Himalayas and North-Eastern India. The GMPE is derived using an efficient nonparametric modelling based on neural network algorithm. In this study, owing to sparsity in the recorded ground motions (498 recordings) for the region, the...

Analytical expressions for displacements and rotations in a homogeneous reduced micropolar half-space subjected to a finite buried source are derived using the method of potentials. Explicit solutions for displacements and rotations are derived for a uniformly distributed force acting over a circular region in the horizontal or vertical direction....

This article characterizes the regions of earthquake slip that are responsible for strong motion generation (SMG), using extreme value theory (EVT). A three-step iterative procedure involving Zipf plot, mean excess function plot and moment ratio plot is used to define the threshold value for a slip model. This threshold slip demarcates the region o...

Plain Language Summary Like Earth, the Moon is also seismically active but with relatively lesser intensity. The seismometers installed by the Apollo missions detected 28 shallow moonquakes during 1969–1977. The moonquake that occurred at Laue crater on 3 January 1975 is the largest recorded moonquake (MW 4.1). Our analysis of high‐resolution satel...

The present study proposes a methodology to generate stochastic slip field with desired probability structure and spectral characteristics. The characterization utilizes 100 tsunamigenic and 130 non-tsunamigenic slip models available in the SRCMOD database. First, the cumulative distribution function (CDF) of marginal slip distributions is obtained...

In this study, a total of 115,246 ground motions recorded during earthquakes of Moment magnitudes ranging from Mw 5.0 to Mw 9.0 are analyzed statistically. A total of 21 ground motion parameters characterising the recorded acceleration time histories are used in the analysis. Classification of these parameters through statistical correlation is rep...

A nonlinear dynamic analysis method in earthquake-resistant design requires real-time ground motion records. However, a definite criterion is required for ground motion selection. In the present study, a damage potential measure ‘distance from zero-amplitude axis (dZ-A)’ is developed through multivariate analysis of 21 different ground motion param...

Amplitude, duration and frequency content are the three key characteristics of a ground motion time history. Few ground motion parameters quantifies two and rarely three of these features. There are even fewer ground motion prediction equations (GMPEs) available for these ground motion parameters. In this study, new GMPEs are derived for a total of...

In this article, a predictive model for ground motion characteristics is developed using the artificial neural network (ANN) technique. This model is developed to predict peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), spectral acceleration at 0.2 and 1 s. The input parameters of the model are moment magn...

The topography of a region significantly affects the ground motions generated during an earthquake. Due to the computational complexities involved, complete three-dimensional analysis of the effect of topography is not studied in detail. The present study tries to understand this effect by simulating ground motions on three-dimensional ridge and va...

Sri Kedarnath temple, located in the Central Seismic Gap in Himalayan region in India is an ancient Hindu temple, which represents India’s rich history of culture, religion, science and technology. The temple structure is composed of concentric enclosures with the innermost sanctum sanctorum roofed with corbelled dome and tapering tower. Multi-leaf...

In the analysis and design of important structures with relatively long life spans, there is a need to generate strong motion data for possible large events. The source of an earthquake is characterized by the spatial distribution of slip on the fault plane. For future events, this is unknown. In this paper, a stochastic earthquake source model is...

The present paper analyzes the effect of Himalayan topography on the characteristics of ground motions due to large earthquake events. A spectral finite element model is developed to simulate ground motions for two past Himalayan earthquakes viz. 2005 Chamoli earthquake and 2011 Sikkim-Nepal border earthquake. The simulations are carried out twice;...

Current seismicity of Mars is poorly known. Geodynamic models and analysis of surface faults indicate that Mars could be seismically active globally, particularly within the Tharsis region. However, published geologic constraints on such activity are sparse. In this study, we use geomorphologic observations and crater size–frequency age determinati...

The present study focuses on developing a 3D crustal velocity model and applying it to perform ground motion simulations for North East India. The study region encompasses area between 89°E to 97°E longitude and 22°N to 30°N latitude. The calibration of the material property is based on 48 shear wave profiles available for the region along with the...

The article aims at developing a stochastic model which simulates spatial distribution of slip on the fault plane. This is achieved by analysing a large dataset of 303 finite-fault rupture models from 152 past earthquakes with varying fault mechanisms and in the magnitude range of 4.11-9.12. New scaling relations to predict the seismic source param...

The present study aims at developing a model for simulating ground motion for earthquakes in the Sumatran region where one of the most devastating earthquakes took place in 2004 with a moment magnitude (Mw) of 9.1. With advancements in instrumentation, the three-dimensional material properties, topography and bathymetry of the region are available...

This article focuses on developing a ground motion prediction equation based on artificial neural network (ANN) technique for shallow crustal earthquakes. A hybrid technique combining genetic algorithm and Levenberg–Marquardt technique is used for training the model. The present model is developed to predict peak ground velocity, and 5% damped spec...

In this article, spatial variation of ground rotational motions is investigated by modelling the Earth medium as linear elastic and reduced micropolar elastic half-spaces. Ground motions are simulated for an earthquake of magnitude Mw 6 and the simulated results are presented in the form of Peak Translation Velocity (PTV) and Peak Rotational Veloci...

The present study aims at developing a new strategy to model the spatial variability of slip on the rupture plane using multi-dimensional ensemble empirical mode decomposition (MEEMD) technique. Here, the earthquake slip distribution is split into finite number of empirical modes of oscillation called the intrinsic mode functions (IMFs). This help...

This paper explores a new method to model and forecast the global earthquake energy release time series. The ISC-GEM catalogue of global events with magnitude Mw≥6.4 is used in this study. The magnitudes of individual events are converted into seismic energy using an empirical relation. The annual earthquake energy time series is constructed by add...

In this study, hybrid simulation technique is used to simulate acceleration time histories for a hypothetical great earthquake of magnitude Mw 8.5 in central seismic gap (CSG) region of Himalaya. In this technique the low frequency ground motions simulated by Spectral Finite Element Method (SPECFEM) are combined with high frequency ground motions o...

The 2011 great Japan Tohoku earthquake (Mw 9.0) is not only the most devastating but also, one of the best recorded earthquakes in the history of seismology. Strong motion characteristics of this earthquake are studied using well established ground motion parameters. A total of 20 parameters are extracted from the data. The behaviour of these param...

In the present study, strong motions are estimated at 17 stations in Southern Peninsular India (SPI) for the 7 February 1900 Coimbatore earthquake (Mw 6) using the empirical Green's function (EGF) method. The broadband recordings of three small earthquakes of ML 3.5, 2.9 and 3.0 respectively, are taken as EGFs to simulate ground motion. The slip di...

In spite of high seismic risk, there is no numerical model of Indo-Gangetic Plain. In this paper, seismic response of the central part of Indo-Gangetic Plain, i.e., Ganga Plain is studied using a 2D plane strain Finite Element model. Seismic source is assumed to be located beneath the Himalayas near Himalayan Frontal Thrust. Basin response is simul...

Empirical approaches based on the available earthquake catalog are popular among engineers to estimate seismic hazard. The seismic activity on individual faults inferred from these approaches is associated with a large number of uncertainties, especially due to lack of data. This article proposes a mechanistic approach to quantify seismic and fault...

One of the most challenging problems in the estimation of seismic hazard is the ability to quantify seismic activity. Empirical models based on the available earthquake catalogue are often used to obtain activity of source regions. The major limitation with this approach is the lack of sufficient data near a specified source. The non-availability o...

This article presents site-specific probable seismic hazard of the Himachal Pradesh province, situated in a seismically active region of northwest Himalaya, using the ground motion relations presented in a companion article. Seismic recurrence parameters for all the documented probable sources are established from an updated earthquake catalogue. T...

This paper explores reduced micropolar theory to simulate ground motion during an earthquake. In this theory, rotational motions are kinematically independent of translational motions. Analytical expressions for ground displacement and rotational motions due to a buried seismic source are presented in this paper. This theory requires two additional...

The seismic activity in the capital city of Delhi is a matter of concern in the design and safety of numerous infrastructure facilities such as buildings, pipelines, railway lines and heritage structures. The city is continuously exposed to several small and large earthquakes due to local and Himalayan earthquake sources. Determination of ground mo...

This article presents four regional site-specific ground motion relations developed for the state of Himachal Pradesh in northwest Himalaya, situated in a seismically active region. These relations are developed from synthetic free surface ground motion databases obtained from a calibrated stochastic seismological model considering the characterist...

In the absence of an array of strong motion records, numerical and empirical methods are used to estimate the ground motion during 25th April 2015 Nepal earthquake. Spectral finite element method is used to simulate low frequency displacements. First, the simulated ground displacement is compared with the recorded data at Kathmandu. The good agreem...

Quantification of seismic activity is one of the most challenging problems faced by earthquake engineers in probabilistic seismic hazard analysis. Currently, this problem has been attempted using empirical approaches which are based on the regional earthquake recurrence relations from the available earthquake catalogue. However, at a specified site...

The spatial distribution of seismic site coefficients at Guwahati is presented in this article. Estimated site coefficients consider different site types in the city and several level of ground shaking consider average of probable seismic event. The evaluation of site coefficients is based on the standard penetration test data at 105 boreholes dist...

Kavitha and Raghukanth (doi:10. 1007/ s40328-015-0131-7, 2015) have developed an algorithm to forecast earthquake energy for a given seismogenic zone. The forecasting strategy is based on empirical mode decomposition and nonlinear regression analysis. The proposed algorithm has been validated with independent subset of seismicity data. Wu (Acta Geo...

Seismic site coefficients (Fs) for Imphal city have been estimated based on 700 synthetically generated earthquake time histories through stochastic finite fault method, considering various combinations of magnitudes and fault distances that may affect Imphal city. Seismic hazard curves and Uniform Hazard Response Spectra (UHRS) are presented for I...

The known surface level ground motion time histories are treated as responses to the unknown double couples on the fault surface. The location, orientation, magnitude and rise time of the double couples are found by minimizing the mean square error between the analytical and recorded solutions. Suitable constraints are used to arrive at physically...

Ground motion relations for east coast region of India

This article explores a new strategy for forecasting of earthquake energy release in the seismogenic zones of the world. A total of 41 active seismogenic zones are identified with the help of past seismicity data. The magnitudes of individual events occurred in each zone are converted into seismic energy using an empirical relation. The annual eart...

Local site conditions can amplify the ground motion in certain frequency ranges and this amplified response should be considered while estimating the design ground motion. In this paper, the results of the in-situ shear wave velocity measurements performed using Multi-channel Analysis of Surface Waves (MASW) tests at some of the prominent locations...

In this article, analytic expressions for the frequency wave number spectra are derived for the displacement and rotational components at the ground surface of a micropolar elastic half-space. The ground motion is caused by buried sources described in terms of unit impulsive force and micro-moments. Closed-form analytic expressions for both plane s...

This article develops a method to generate ground motion time histories that maximize the response of a given linearly elastic structure. The root mean square (RMS) level of the input power spectral density (PSD) is used as a strong motion parameter. It is related to seismological data that is readily available. An empirical relation to estimate RM...

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