A5101681422- Seismic Imaging and Inversion Techniques
- Seismic Waves and Analysis
- Hydraulic Fracturing and Reservoir Analysis
- Geophysical Methods and Applications
- Reservoir Engineering and Simulation Methods
- Drilling and Well Engineering
- earthquake and tectonic studies
- Geophysical and Geoelectrical Methods
- Hydrocarbon exploration and reservoir analysis
- Underwater Acoustics Research
- High-pressure geophysics and materials
- Methane Hydrates and Related Phenomena
- Electromagnetic Simulation and Numerical Methods
- Geological and Geochemical Analysis
- Numerical methods in engineering
- Image and Signal Denoising Methods
- Seismology and Earthquake Studies
- Atmospheric and Environmental Gas Dynamics
- Advanced Numerical Methods in Computational Mathematics
- NMR spectroscopy and applications
- Geophysics and Gravity Measurements
- Geological Modeling and Analysis
- CO2 Sequestration and Geologic Interactions
- Geophysics and Sensor Technology
- Rock Mechanics and Modeling
The University of Texas at Austin
2016-2025
University of Texas Institute for Geophysics
2007-2018
National Geophysical Research Institute
2009-2015
Geophysical Laboratory
2013
National Institute of Disaster Management
2013
Ministry of Earth Sciences
2013
China University of Petroleum, Beijing
2009-2011
Commonwealth Scientific and Industrial Research Organisation
2011
Curtin University
2011
Geological Survey of Canada
2010
The seismic inverse problem involves finding a model m that either minimizes the error energy between data and theoretical seismograms or maximizes cross‐correlation synthetics observations. We are, however, faced with two problems: (1) space is very large, typically of order [Formula: see text]; and, (2) function multimodal. Existing calculus‐based methods are local in scope easily get trapped minima function. Other such as “simulated annealing” “genetic algorithms” can be applied to global...
Seismic waveform inversion is one of many geophysical problems which can be identified as a nonlinear multiparameter optimization problem. Methods based on local linearization fail if the starting model too far from true model. We have investigated applicability “Genetic Algorithms” (GA) to plane‐wave seismograms. Like simulated annealing, genetic algorithms use random walk in space and transition probability rule help guide their search. However, unlike single annealing run, search randomly...
An inversion algorithm is commonly used to estimate the elastic properties, such as P-wave velocity ([Formula: see text]), S-wave and density text]) of earth’s subsurface. Generally, seismic problem solved using one traditional optimization algorithms. These algorithms start with a given model update at each iteration, following physics-based rule. The applied common depth point (CDP) independently parameters. Here, we have developed technique convolutional neural network (CNN) solve same...
Abstract The posterior probability density function (PPD), σ(m|d obs ), of earth model m, where d are the measured data, describes solution a geophysical inverse problem, when Bayesian inference is used to describe problem. In many applications, PPD neither analytically tractable nor easily approximated and simple analytic expressions for mean variance not available. Since complete description impossible in highly multi‐dimensional space several measures such as highest regions, marginal...
The seismic waveform inversion problem is usually cast into the framework of Bayesian statistics in which prior information on model parameters combined with data and physics forward to estimate a posteriori probability density (PPD) space. PPD function an objective or fitness computed from observed synthetic data. In general, multimodal its shape unknown. Global optimization methods such as simulated annealing (SA) genetic algorithms (GA) do not require that be known. this paper, we...
Purely numerical methods based on finite-element approximation of the acoustic or elastic wave equation are becoming increasingly popular for generation synthetic seismograms. We present formulas grid dispersion and stability criteria some (FEM) propagation, namely, classical spectral FEM. develop an approach a generalized eigenvalue formulation to analyze dispersive behavior these FEMs propagation that overcomes difficulties caused by irregular node spacing within element use high-order...
Recently, there has been an increased interest in applying the discontinuous Galerkin method (DGM) to wave propagation. In this work, we investigate applicability of interior penalty DGM elastic propagation by analysing it's grid dispersion properties, with particular attention effect that different basis functions have on numerical dispersion. We consider types naturally yield a diagonal mass matrix. This is relevant seismology because matrix tantamount explicit and efficient time marching...
We derive explicit and new implicit staggered-grid finite-difference (FD) formulas for derivatives of first order with any accuracy by a plane wave theory Taylor's series expansion. Furthermore, we arrive at practical algorithm such that the tridiagonal matrix equations are formed FD derived from fractional expansion derivatives. Our results demonstrate (2N+ 2)th-order formula is nearly equivalent to or greater than (4N)th-order formula. The method only involves solving equations. also...
Resolving thin layers and clearly delineating layer boundaries in inverted seismic sections are very important goals for exploration production. Many inversion methods based on a least-squares optimization approach with Tikhonov-type regularization can lead to unfocused transitions between adjacent layers. A basis pursuit (BPI) algorithm the [Formula: see text] norm method can, however, resolve sharp We have formulated BPI amplitude-versus-angle investigated its potential improve contrasts...
We propose a new time‐space domain finite difference formula with arbitrary order accuracy for acoustic wave equation modeling which has been derived using plane theory. The is 2nd‐order when conventional 2M‐order space finite‐difference and time stencils are directly used to solve an 1D equation. However, the can reach same discretization our method. advantages of method demonstrated by results dispersion analysis numerical modeling. two‐dimensional also shown. presented in this paper be...
Prestack or angle stack gathers are inverted to estimate pseudologs at every surface location for building reservoir models. Recently, several methods have been proposed increase the resolution of All these methods, however, require that total number model parameters be fixed a priori. We investigated an alternate approach in which we allow data themselves choose parameterization. In other words, addition layer properties, layers is also treated as variable our formulation. Such...
Full-waveform inversion (FWI) has become a popular method to estimate elastic earth properties from seismograms. It is formulated as data-fitting least-squares minimization problem that iteratively updates an initial velocity model with the scaled gradient of misfit until satisfactory match between real and synthetic data obtained. However, such local optimization approach can converge minimum if starting used not close enough optimal model. We have developed two-step process in which we...
Elastic reverse time migration (RTM) can yield accurate subsurface information (e.g. PP and PS reflectivity) by imaging the multicomponent seismic data. However, existing RTM methods are still insufficient to provide satisfactory results because of finite recording aperture, limited bandwidth imperfect illumination. Besides, P- S-wave separation polarity reversal correction indispensable in conventional elastic RTM. Here, we propose an iterative least-squares (LSRTM) method, which accuracy...
We show that the linearized reflection coefficients for arbitrary anisotropic media embedded in an isotropic background can be derived directly from a Born formalism. Due to rapidly varying phases of scattered waves first‐order perturbations density and elastic parameters, major contributions observed wavefield any source–receiver pair far volume scatterers arise stationary points scattering integral, called integral. For simple interface models, such integrals evaluated analytically using...
Abstract Although climate models have steadily improved their ability to reproduce the observed climate, over years there has been little change wide range of sensitivities exhibited by different a doubling atmospheric CO2 concentrations. Stochastic optimization is used mimic how six independent model development efforts might use same general circulation model, set observational constraints, and skill criteria choose settings for parameters thought be important sources uncertainty related...
Microstructural attributes of cracks and fractures, such as crack density, aspect ratio, fluid infill, determine the elastic properties a medium containing set parallel, vertical fractures. Although tangential weakness [Formula: see text] fractures does not vary with content, normal exhibits significant dependence on infill. Based linear-slip theory, we used ratio — termed indicator quantitative measure content in g representing square S- P-wave velocity unfractured medium. We Born formalism...
One source of uncertainty for climate model predictions arises from the fact that models have been optimized to reproduce observational means. To quantify resulting a realistic range configurations, it is necessary estimate multidimensional probability distribution quantifies how likely different parameter combinations are, given knowledge uncertainties in observations. The computational cost mapping using traditional means (e.g., Monte Carlo or Metropolis/Gibbs sampling) impractical,...
We propose an efficient scheme to absorb reflections from the model boundaries in numerical solutions of wave equations. This divides computational domain into boundary, transition, and inner areas. The wavefields within boundary areas are computed by equation one-way equation, respectively. transition area determined a weighted combination obtain smooth variation via zone. results our finite-difference modeling tests 2D acoustic show that absorption enforced this gradually increases with...
We investigate the stability of some high-order finite element methods, namely spectral method and interior-penalty discontinuous Galerkin (IP-DGM), for acoustic or elastic wave propagation that have become increasingly popular in recent past. consider Lax-Wendroff (LWM) time stepping show it allows a larger step than classical leap-frog difference method, with higher-order accuracy. In particular fourth-order LWM 73 per cent method; computational cost is approximately double step, but...
Abstract The lithospheric structure of the Indian plate has been investigated using converted wave techniques ( P and S receiver functions) a novel stacking analysis technique (without deconvolution) applied to large seismological data set from permanent temporary broadband seismic stations. We observe coherent energy at least two discontinuities, i.e., crust‐mantle (Moho) lithosphere‐asthenosphere boundary (LAB) in uppermost mantle. Here we provide image lithosphere showing definitive...
The staggered-grid finite-difference (SFD) method is widely used in numerical modeling of wave equations.Conventional SFD stencils for spatial derivatives are usually designed the space domain.However, when they to solve equations, it becomes difficult satisfy dispersion relations exactly.Liu and Sen (2009c) proposed a new scheme one-dimensional (1D) scalar equation based on time-space domain relation plane theory, which made exact relation.This has greater accuracy better stability than...
Abstract Artificial water reservoir-triggered earthquakes have continued at Koyna in the Deccan Traps province, India, since impoundment of Shivaji Sagar reservoir 1962. Existing models, to comprehend genesis triggered earthquakes, suffer from lack observations near field. To investigate further, scientific deep drilling and setting up a fault zone observatory depth 5–7 km is planned area. Prior undertaking drilling, an exploratory phase investigations has been launched constrain subsurface...