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Lateral variations in attenuation an...

University of California, Berkeley.

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Lateral variations in attenuation and anisotropy of the upper mantle from seismic waveform tomography.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Lateral variations in attenuation and anisotropy of the upper mantle from seismic waveform tomography./
作者:	Gung, Yuan-Cheng.
面頁冊數:	138 p.
附註:	Chair: Barbara Romanowicz.
Contained By:	Dissertation Abstracts International65-02B.
標題:	Geophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoeng/servlet/advanced?query=3121506
ISBN:	9780496688579

Lateral variations in attenuation and anisotropy of the upper mantle from seismic waveform tomography.
Gung, Yuan-Cheng.

Lateral variations in attenuation and anisotropy of the upper mantle from seismic waveform tomography. - 138 p.

Chair: Barbara Romanowicz.

Thesis (Ph.D.)--University of California, Berkeley, 2003.

We present constraints on Earth's upper mantle structure from seismic tomography. Using the well established waveform inversion technique for seismic velocity, we extend this mode-perturbation-based approach to resolve anelasticity and anisotropy. We develop an inversion procedure for Q tomography involving two steps: (1) 3D whole-mantle velocity models are first derived using nonlinear asymptotic coupling theory, which takes into account across-branch coupling effects among Earth's normal modes; and (2) the surface waveforms thus aligned in phase are inverted to obtain a degree 8 upper mantle Q model, QRLW8. Various stability tests are performed to assess the quality of the model, and in particular to assess possible contamination from focusing effects. We find that the 3D patterns obtained are stable, but the amplitude of the lateral variation in Q is not well constrained. By comparing the Q model to velocity models, we address its implications for thermal upwellings, mantle dynamics and heat flux. We also develop an inversion procedure for transverse anisotropy using three-component surface and body waveform data. The procedure combines non-linear asymptotic theory and appropriate anisotropy kernels for weak transverse anisotropy. The resulting degree 16 model (SAW16AN) shows that significant radial anisotropy with VSH > VSV is present under most cratons in the depth range 250--400 km. This explains the lack of correlation among global tomographic models derived from different groups at this depth range. It also leads us to propose a new interpretation of the thickness of seismically defined tectosphere.

ISBN: 9780496688579Subjects--Topical Terms:

535228
Geophysics.

Lateral variations in attenuation and anisotropy of the upper mantle from seismic waveform tomography.
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502 $a Thesis (Ph.D.)--University of California, Berkeley, 2003.
520 $a We present constraints on Earth's upper mantle structure from seismic tomography. Using the well established waveform inversion technique for seismic velocity, we extend this mode-perturbation-based approach to resolve anelasticity and anisotropy. We develop an inversion procedure for Q tomography involving two steps: (1) 3D whole-mantle velocity models are first derived using nonlinear asymptotic coupling theory, which takes into account across-branch coupling effects among Earth's normal modes; and (2) the surface waveforms thus aligned in phase are inverted to obtain a degree 8 upper mantle Q model, QRLW8. Various stability tests are performed to assess the quality of the model, and in particular to assess possible contamination from focusing effects. We find that the 3D patterns obtained are stable, but the amplitude of the lateral variation in Q is not well constrained. By comparing the Q model to velocity models, we address its implications for thermal upwellings, mantle dynamics and heat flux. We also develop an inversion procedure for transverse anisotropy using three-component surface and body waveform data. The procedure combines non-linear asymptotic theory and appropriate anisotropy kernels for weak transverse anisotropy. The resulting degree 16 model (SAW16AN) shows that significant radial anisotropy with VSH > VSV is present under most cratons in the depth range 250--400 km. This explains the lack of correlation among global tomographic models derived from different groups at this depth range. It also leads us to propose a new interpretation of the thickness of seismically defined tectosphere.
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