P- and S-wave Tomography of the Crust and
Uppermost Mantle in China and Surrounding Areas
by
Youshun Sun
Submitted
to the Department of Earth, Atmospheric, and Planetary Sciences on June 1, 2005 in partial fulfillment of the requirements for the
degree of Doctor of Philosophy
ABSTRACT
This thesis involves inverting the seismic structure of the crust and uppermost mantle in
China from the P- and S-wave travel-time tomography. The main contributions of this
research are: 1) introducing the adaptive moving window method to obtain 2338 1D P
and S models in China; 2) introducing a tomographic method to perform the 3D body
wave travel-time tomography with the Moho discontinuity included. Both horizontal and
vertical resolutions are highly controlled and smooth transitions among adjacent locations
are guaranteed in the final models. To achieve these objectives, the Mone-Carlo (random
search) method and the Gauss-Newton method are applied iteratively to find the
nonlinear least square solutions and to optimize the models in the crust and uppermost
mantle. The models we obtained provide accurate travel-time calculation, ground-truth
event relocation and seismogram fittings. These models can therefore be applied to
reliable earthquake location.
Geological, geodynamic, and volcanic implications of our models are discussed in this
thesis. Our tomographic models provide new insights into the geological structure and
tectonics of the region, such as lithological variations and large fault zones across the
major geological terranes. Compared with previous tomographic studies, we have used a
larger, higher quality data set and applied an updated tomographic method to take into
account the effects of the complex Moho geometry in this region. Our results cast a new
light over the complex structure and seismotectonics of China and surrounding areas.
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October 5, 2005
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