| Multi-Grid and Resolution Full-Wave Tomography and Moment Tensor Inversion (Postprint) |
04 Jun 2012 |
14 pages |
| Authors:
Yang Shen; Wei Zhang; RHODE ISLAND UNIV KINGSTON
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 | There is a general consensus that 3D reference models can be used to isolate effects of wave propagation and thus help in improving characterization of seismic sources. Advances in computation and numerical method have made it possible to capture increasingly broadband, full wave generation and propagation in 3D earth models. The main objectives of this project are to construct hierarchical, multi-grid (resolution) joint P and S velocity models and the ... |
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| Full-wave Moment Tensor and Tomographic Inversions Based on 3D Strain Green Tensor |
31 Jan 2010 |
134 pages |
| Authors:
Yang Shen; Xiaoping Yang; SCIENCE APPLICATIONS INTERNATIONAL CORP (SAIC) ARLINGTON VA
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| We developed a unified source moment tensor and tomographic inverse method based on finite difference simulations of wave propagation at local to teleseismic distances. The new method accounts for complex wave propagation in three-dimensional (3D) earth, linearizes the inverse problem by iteratively updating the earth model, and provides an accurate way to integrate body- and surface-wave observations. The finite-difference methods developed to date make it possible to construct hierarchical FD-SGT ... |
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| Unified Regional Tomography and Source Moment Tensor Inversions Based on Finite-Difference Strain Green Tensor Databases |
30-Sep-2009 |
11 pages |
| Authors:
Wei Zhang; Xiaoping Yang; Yang Shen; Li Zhao; Zhigang Zhang; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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| Seismic monitoring requires accurate source characterization in real time. Accurate 3D earth models are essential for accurate predictions of seismic observables and source characterization. While recovering the true earth structure has always been the goal of tomographic inversions, methods based on full wavefields in 3D reference models have several distinct advantages. Made possible by advances in high-performance computation, this full-wave approach accounts for complex wave propagation in 3D heterogeneous earth, ... |
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| Developments of Finite-Frequency Seismic Theory and Applications to Regional Tomographic Imaging |
31-Jan-2009 |
54 pages |
| Authors:
Xiaoping Yang; Yang Shen; SCIENCE APPLICATIONS INTERNATIONAL CORP (SAIC) ARLINGTON VA
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| We use banana-doughnut sensitivity kernels of teleseismic body waves to image the crust and mantle beneath eastern Eurasia. We have collected and processed available broadband data from both permanent stations and temporary networks in eastern Eurasia. In southeast Tibet, where a PASSCAL experiment provided a dense station coverage, a detailed study is carried out to obtain high-resolution P- and Svelocity models. A regional P-wave velocity model for eastern Eurasia is ... |
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| Finite-Frequency Seismic Tomography of Body Waves and Surface Waves from Ambient Seismic Noise: Crustal and Mantle Structure Beneath Eastern Eurasia |
30-Sep-2008 |
11 pages |
| Authors:
Yong Ren; Wei Zhang; Ting Yang; Yang Shen; Xiaoping Yang; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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| To improve seismic calibration for nuclear explosion monitoring, we use 3D sensitivity kernels of finite-frequency body and surface waves to develop models of the crustal and mantle structures beneath eastern Eurasia. We have collected and processed available broadband data from both permanent stations and temporary networks in eastern Eurasia. We obtained a regional P-wave velocity model for the mantle structures down to 1,500 km beneath the eastern Eurasia. We also ... |
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| Refined Local and Regional Seismic Velocity and Attenuation Models from Finite-Frequency Waveforms |
30-Sep-2008 |
11 pages |
| Authors:
Wei Zhang; Yang Shen; Li Zhao; Xiaoping Yang; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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| In seismic tomography, the reference or starting models are commonly one-dimensional (1D) and the structural sensitivity kernels of seismic data are calculated without considering the finiteness of seismic waves in both time and frequency domains. These simplifications result in a theoretical limit, in addition to that from the data coverage, on the structural resolution in tomography inversions. In small-scale (such as the crustal) structural imaging, however, a higher resolution is ... |
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| Finite Frequency Seismic Tomography for Eastern Eurasia |
21 Sep 2006 |
10 pages |
| Authors:
Ting Yang; Yang Shen; Xiaoping Yang; SCIENCE APPLICATIONS INC SAN DIEGO CA
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| Seismic calibration for nuclear explosion monitoring requires accurate, high-resolution 3-D velocity models. Although seismic event locations have been improved recently using more accurate travel times measured by waveform cross-correlation, ray-based models and predictions are not strictly self-consistent with travel times measured by waveform cross-correlation, which are sensitive to 3-D velocity perturbations around the geometric ray paths. Finite-frequency seismic tomography (FFST), which utilizes the 3-D sensitivity kernels to determine the structure ... |
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| Developing Finite-Frequency Regional Pn Velocity Models |
Sep 2006 |
9 pages |
| Authors:
Zhigang Zhang; Yang Shen; Li Zhao; Xiaoping Yang; Kim Olsen; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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| Head waves and Pn waves in particular are important in studying the predominantly layered velocity structure of the Earth and discriminating the seismic sources. Conventional studies of head waves have used high-frequency (ray) approximation in wave propagation. While recent studies have shown the diffractive nature and the three dimensional (3-D) sensitivities of finite-frequency turning waves, analogs of head waves in a continuous velocity structure, the finite-frequency effects and sensitivity kernels ... |
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