1. Jilin University, College of Geoexploration Science and Technology, Changchun, China; visiting University of British Columbia, Vancouver, Canada. .
2. University of British Columbia, Department of Electrical and Computer Engineering, Vancouver, Canada. .
3. University of British Columbia, Department of Mathematics, Vancouver, Canada. .
4. University of British Columbia, Seismic Laboratory for Imaging and Modeling, Department of Earth and Ocean Sciences, Vancouver, Canada. .