Acknowledgments

We would like to thank Tingting Liu, Zhaoyu Jin, and Wei Liu for helpful comments and suggestions on the topic of EMD. We are grateful to developers of the Madagascar software package for providing corresponding codes for testing the algorithms and preparing the figures. This research is supported by Sinopec Key Laboratory of Geophysics (Grant No. 33550006-15-FW2099-0017) and Texas Consortium for Computational Seismology (TCCS).