Acknowledgments

I would like to thank editors Jorg Renner, Lapo Boschi, and two anonymous reviewers for providing critical comments that improve the manuscript greatly. I also thank Shuwei Gan, Shaohuan Zu, Weilin Huang for helpful comments and suggestions on the topic of seismic signal processing, and Jianwei Ma, Sergey Fomel, Siwei Yu for inspiring discussions on sparse transform.