Download or read book Three dimensional Inversion of Magnetotelluric Data from the Coso Geothermal Field Based on a Finite Difference Gauss Newton Method Parallelized on a Multicore Workstation written by Virginie Maris and published by . This book was released on 2011 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Three dimensional Inversion of Large scale EarthScope Magnetotelluric Data Based on the Integral Equation Method written by Michael S. Zhdanov and published by . This book was released on 2011 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: [1] Interpretation of the EarthScope MT (magnetotelluric) data requires the development of a large-scale inversion method which can address two common problems of 3D MT inversion: computational time and memory requirements. We have developed an efficient method of 3D MT inversion based on an IE (integral equation) formulation of the MT forward modeling problem and a receiver footprint approach, implemented as a massively parallel algorithm. This method is applied to the MT data collected in the western United States as a part of the EarthScope project. As a result, we present one of the first 3D geoelectrical images of the upper mantle beneath Yellowstone revealed by this large-scale 3D inversion of the EarthScope MT data. These images show a highly conductive body associated with the tomographically imaged mantle plume-like layer of hot material rising from the upper mantle toward the Yellowstone volcano. The conductive body identified in these images is west-dipping in a similarway to a P-wave low-velocity body.
Download or read book Two dimensional Modeling and Inversion of the Controlled source Electromagnetic and Magnetotelluric Methods Using Finite Elements and Full space PDE constrained Optimization Strategies written by Savitri Galiana Blanch and published by . This book was released on 2016 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The controlled-source electromagnetics (CSEM) and magnetotellurics (MT) methods arecommon geophysical tools for imaging the electrical properties of the Earth's subsurfaceand are employed independently, jointly, and in combination with other geophysical tech-niques. In order to appreciate measured data, both methods require forward and inversemodeling of the electrically conductive subsurface with the ultimate goal of finding a fea-sible model for which the simulated data reasonably fits the observations. Naturally, thepotential goodness of this fit not only depends on the error in the measured data and on thenumerical error but also on the degree of physical approximation inferred by numericalmodeling. Therefore, active research focuses on new methods for modeling and inversionto obtain accurate and reliable models of the Earth's structure in increasingly complexscenarios. A first step is to enhance modeling approximations by taking into account physical fac-tors such as anisotropy, topography or realistic sources. Second, in order to accommodatethese factors in a modeling and inversion program and to deal with typically large datasets, numerical methods need to be assessed in terms of solution accuracy, time efficiencyand memory demand. The finite elements (FE) modeling methods are known to offer mostflexibility in model geometry and contain quality control mechanisms for the solution, likeshape function order and adaptive mesh refinement. Most emerging modeling programsare based on FE, appreciating significant advantages, but nearly all inverse modeling pro-grams to date are still based on finite differences (FD) or integral equation (IE) methods. Furthermore, inverse modeling developed for electromagnetic (EM) data is generallybased on gradient methods and is formulated in a reduced space, where the only optimiza-tion variables are the model parameters, that is the electric conductivity of the subsurface. Originally, the inverse problem is stated for the EM fields and the conductivity parameter, and constrained by partial differential equations (PDEs) governing the EM field variables. The reduced-space strategy eliminates the field variables by applying equality constraintsand solving then, the unconstrained problem in the reduced-space of model parameters. Acommon drawback of such methods is the repeated costly computation of the solution ofthe forward problem and of the Jacobian matrix of sensitivities (for Newton's based meth-ods). In contrast, it is also possible to solve the inverse problem in the full-space of modelparameters, including both the EM field variables and the electric conductivity parameter. Solving the PDE-constrained optimization problem directly (full-space) has the advantagethat it is only necessary to solve exactly the PDEs at the very end of the optimization provicess but it comes at the cost of many more optimization variables and of the presence ofequality constraints. Also, in particular, within a FE framework, the PDE-constrained op-timization problem provides the additional benefit to include sophisticated FE techniquesin the inversion process, such as adaptive mesh refinement. This thesis develops a robust and versatile adaptive unstructured mesh FE programto numerically model the total field for two-dimensional (2-D) anisotropic CSEM and MTdata, allowing for arbitrarily oriented, three-dimensional (3-D) sources. To represent 3-DCSEM sources for a 2-D physical model, a two-and-a-half-dimensional (2.5-D) approxi-mation is employed. The FE formulations are derived for both methods, for isotropic andanisotropic subsurface conductivity structures. Although the anisotropic case is not general, it includes vertical and dipping anisotropy. The accuracy of the solution is controlledand improved by an adaptive mesh refinement algorithm usinga-posteriorierror estimator methods."--TDX.
Download or read book Phonetics Theory and Application written by William R. Tiffany and published by McGraw-Hill Humanities, Social Sciences & World Languages. This book was released on 1977 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Future Energy Grid written by Hans-Jürgen Appelrath and published by . This book was released on 2012 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt:
