Browsing by Author "Liu, Huafeng"

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    An explicit time evolution method for acoustic wave propagation
    (Society of Exploration Geophysicists, 2014) Liu, Huafeng; Dai, Nanxun; Niu, Fenglin; Wu, Wei
    Cost-effective waveform modeling is the key to practical reverse time migration (RTM) and full-waveform inversion (FWI) implementations. We evaluated an explicit time evolution (ETE) method to efficiently simulate wave propagation in acoustic media with high temporal accuracy. We started from the constant-density acoustic wave equation and obtained an analytical time-marching scheme in the wave number domain. We then formulated an ETE scheme in the time-space domain by introducing a cosine function approximation. Although the ETE operator appears to be similar to the second-order temporal finite-difference (FD) operator, the exact nature of the ETE formula ensures high accuracy in time. We further introduced a set of optimum stencils and coefficients by minimizing evolution errors in a least-squares sense. Our numerical tests indicated that ETE can achieve similar waveform accuracy as FD with four times larger time steps. Meanwhile, the compact ETE operator keeps the computation efficient. The efficiency and capability to handle complex velocity field make ETE an attractive engine in acoustic RTM and FWI.
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    Receiver Function Analysis and Acoustic Waveform Modeling for Imaging Earth’s Crust: New Techniques and Their Applications
    (2013-09-16) Liu, Huafeng; Niu, Fenglin; Gordon, Richard G.; Zelt, Colin A.; Symes, William W.
    The crust is the outer-most layer of the earth with thickness up to 80 km. Massive seismic waveform data have enabled imaging fine crustal structures with the aid of new imaging techniques. In this thesis, I develop seismic imaging techniques to take full