A multiscale hypothesis testing approach to anomaly detection and localization from noisy tomographic data

Includes bibliographical references (p. 29-30).Supported by Air Force Office of Scientific Research. F49620-95-1-0083, F49620-96-1-0028 (awarded to Boston University) Supported by a National Defense Science and Engineering Graduate Fellowship awarded by the Defense Advanced Research Projects Agency. F49620-93-1-0604Austin B. Frakt, W. Clem Karl, Alan S. Willsky

Computational Inverse Problems

Inverse problem typically deal with the identification of unknown quantities from indirect measurements and appear in many areas in technology, medicine, biology, finance, and econometrics. The computational solution of such problems is a very active, interdisciplinary field with close connections to optimization, control theory, differential equations, asymptotic analysis, statistics, and probability. The focus of this workshop was on hybrid methods, model reduction, regularization in Banach spaces, and statistical approaches

Book of Abstracts

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Applications on Ultrasonic Wave

This book presents applications on the ultrasonic wave for material characterization and nondestructive evaluations. It could be of interest to the researchers and students who are studying on the fields of ultrasonic waves

Seismological forward and inverse modelling for upper mantle seismic anisotropy studies

Seismic anisotropy is the dependence of seismic wave velocity on the propagation direction and it is mainly generated by strain-induced lattice preferred orientation (LPO) of intrinsically anisotropic minerals. Despite previous studies have demonstrated that neglecting anisotropy introduces notable imaging artifacts, most tomographic methods rely on the assumption of isotropy, interpreting fast and slow velocity anomalies as related to seismically isotropic sources (e.g., temperature anomalies, presence of a liquid phase, etc). In this Thesis we carried out numerical simulations aiming at improving strain-induced fabric estimates and predicting realistic elastic properties in 2-D and 3-D synthetic domains. We generated synthetic datasets with forward waveform modelling and explored different inverse methodologies (e.g., P- and S-wave travel time tomography, automatic partitioned waveform inversion of surface waves) both with real and synthetic data. Among the results, we present ani-NEWTON21, the first 3D anisotropic teleseismic P-wave tomography revealing upper mantle structures and dynamics beneath the Central Mediterranean. By performing synthetic seismic data inversions we tested how ray density, data quality and regularization (i.e., damping and smoothing factors) influence the tomographic image. Finally, from the comparison of purely isotropic and anisotropic tests, we observed that the first-order effect of including anisotropy in the inversion is to reduce the magnitude of isotropic anomalies, more significantly for low-velocity zones relative to high-velocity zones. The research activities described in this Thesis altogether provide important insights for predicting and isolating seismic anisotropy, and for obtaining more reliable and physically consistent imaging of the Earth’s internal structure.Seismic anisotropy is the dependence of seismic wave velocity on the propagation direction and it is mainly generated by strain-induced lattice preferred orientation (LPO) of intrinsically anisotropic minerals. Despite previous studies have demonstrated that neglecting anisotropy introduces notable imaging artifacts, most tomographic methods rely on the assumption of isotropy, interpreting fast and slow velocity anomalies as related to seismically isotropic sources (e.g., temperature anomalies, presence of a liquid phase, etc). In this Thesis we carried out numerical simulations aiming at improving strain-induced fabric estimates and predicting realistic elastic properties in 2-D and 3-D synthetic domains. We generated synthetic datasets with forward waveform modelling and explored different inverse methodologies (e.g., P- and S-wave travel time tomography, automatic partitioned waveform inversion of surface waves) both with real and synthetic data. Among the results, we present ani-NEWTON21, the first 3D anisotropic teleseismic P-wave tomography revealing upper mantle structures and dynamics beneath the Central Mediterranean. By performing synthetic seismic data inversions we tested how ray density, data quality and regularization (i.e., damping and smoothing factors) influence the tomographic image. Finally, from the comparison of purely isotropic and anisotropic tests, we observed that the first-order effect of including anisotropy in the inversion is to reduce the magnitude of isotropic anomalies, more significantly for low-velocity zones relative to high-velocity zones. The research activities described in this Thesis altogether provide important insights for predicting and isolating seismic anisotropy, and for obtaining more reliable and physically consistent imaging of the Earth’s internal structure

GEODYNAMIC AND SEISMOLOGICAL MODELLING OF THE CENTRAL-WESTERN MEDITERRANEAN MID-LATE CENOZOIC DYNAMICS AND STRUCTURE.

The Central-Western Mediterranean is one of the most complex tectonic settings on Earth. The articulate lithospheric structure currently observed in the region is the result of manifold tectonic processes that have occurred since the Mid-Late Cenozoic. Despite its shallow tectonic evolution has been relatively well constrained by a wealth of geological and geophysical data, several uncertainties persist about the recent mantle dynamics and the mechanisms that led to the present-day surface morphology and deep slab geometry. This Thesis attempt to reproduce the recent large-scale evolution of the Central-Western Mediterranean and the associated strain-induced upper mantle fabrics and seismic anisotropy adopting a strategy that combines geodynamic and seismological numerical modelling techniques. We explore a wide range of models and evaluate the modelling results by comparing seismological synthetics and the predicted tectonic evolution with geophysical and geological observations. The good correlation between modelled and observed slab morphology and seismic anisotropy patterns poses new important constraints on the tectonic evolution of the study area, explaining the major tectonic events proposed in the literature (e.g., the rotation of the Sardinian-Corsican block and the opening of back-arc basins related to the retreat of the Ionian trench, the lateral tearing and breakoff of oceanic slabs, etc..) that have contributed to shaping the Central-Western Mediterranean. The research activities demonstrate that this methodology can capture to a first order the overall evolution and the current geological scenario of the study region, thus representing a powerful tool to investigate mantle dynamics. Furthermore, geodynamic models were exploited to test the capabilities and limitations of P- and S-waves anisotropic inversions, showing that inverting for seismic anisotropy allows to avoid notable imaging artefacts and, consequently, errors in the interpretation of the tomographic results.The Central-Western Mediterranean is one of the most complex tectonic settings on Earth. The articulate lithospheric structure currently observed in the region is the result of manifold tectonic processes that have occurred since the Mid-Late Cenozoic. Despite its shallow tectonic evolution has been relatively well constrained by a wealth of geological and geophysical data, several uncertainties persist about the recent mantle dynamics and the mechanisms that led to the present-day surface morphology and deep slab geometry. This Thesis attempt to reproduce the recent large-scale evolution of the Central-Western Mediterranean and the associated strain-induced upper mantle fabrics and seismic anisotropy adopting a strategy that combines geodynamic and seismological numerical modelling techniques. We explore a wide range of models and evaluate the modelling results by comparing seismological synthetics and the predicted tectonic evolution with geophysical and geological observations. The good correlation between modelled and observed slab morphology and seismic anisotropy patterns poses new important constraints on the tectonic evolution of the study area, explaining the major tectonic events proposed in the literature (e.g., the rotation of the Sardinian-Corsican block and the opening of back-arc basins related to the retreat of the Ionian trench, the lateral tearing and breakoff of oceanic slabs, etc..) that have contributed to shaping the Central-Western Mediterranean. The research activities demonstrate that this methodology can capture to a first order the overall evolution and the current geological scenario of the study region, thus representing a powerful tool to investigate mantle dynamics. Furthermore, geodynamic models were exploited to test the capabilities and limitations of P- and S-waves anisotropic inversions, showing that inverting for seismic anisotropy allows to avoid notable imaging artefacts and, consequently, errors in the interpretation of the tomographic results

ALERT Doctoral School 2012: advanced experimental techniques in geomechanics

The twenty-second session of the European Graduate School 2012 (called usually ALERT Doctoral School) entitled Advanced experimental techniques in geomechanics is organized by Cino Viggiani, Steve Hall and Enrique Romero.Postprint (published version