Sheng Wang’s Ph.D. work has been instrumental in establishing a global earthquake late-coda correlation wavefield as a paradigm that represents an elegant and powerful way to explore the interiors of Earth and other planets. He is an outstanding early-career scholar, competent, creative, and hardworking, and also kind and considerate to all. However, what distinguishes Sheng from many of his peers worldwide is that he is not afraid to take on challenges; he is not afraid of obstacles that might present themselves in uncharted territory. Sheng’s work on global late-coda cross correlation was pivotal in enhancing the quality of the global cross-correlation stacks. However, methodological advances have never been his primary drive; what truly drives him is his curiosity to solve the most outstanding questions in studies of Earth’s deep interior. An early result of his endeavors as a graduate student was the observational evidence of how the global correlation wavefield is formed. He further showed that Earth’s deep interior can be illuminated by “coda-correlation tomography” using the waves that reverberate multiple times after being excited by an earthquake. These groundbreaking results earned him highlights by two journal editors independently and were among the key contributions in two invited review papers. More important, they laid the foundation for the new spherically symmetric Earth model based only on the similarity of waveforms many hours after large earthquakes and aided new research on P wave inner core anisotropy. Subsequently, Sheng probed the inner core shear anisotropy, a problem that has been considered notoriously difficult due to the lack of observations of these waves. He confirmed our earlier results that the J waves can be observed, and discovered that they travel faster for at least approximately 5 seconds in directions oblique to the Earth’s rotation axis than in directions parallel to the equatorial plane. As his supervisor, it gives me joy to say that the above was only a fraction of Sheng’s achievements. Namely, his Ph.D. work led to a demonstration that instead of an interstation correlation wavefield, it is possible to use the intersource correlation wavefield by virtue of reciprocity on the global scale. Consequently, he demonstrated that a single receiver could produce Earth’s correlation “fingerprint.” This opened a way of scanning for the planetary cores based on a single seismograph, resulting in confirmation that Mars has a large core. For these reasons, Sheng Wang is a highly deserving recipient of the Study of the Earth’s Deep Interior Section Award for Graduate Research. —Hrvoje Tkalčić, Australian National University, Canberra, A.C.T.

I am deeply honored to be a recipient of this award. This could not have happened without the guidance, support, and help of my mentors, collaborators, and friends. It would be impossible to mention all of them, but I would like to thank at least some of them. Thank you, Hrvoje, for your generous citation and nomination, and also for the challenging but fascinating Ph.D. journey with you. Many years later, looking back, I will still remember the start of this journey, a picture of a sunny and warm autumn afternoon with golden leaves falling quietly outside the window, and you on the other side of an old desk asked me, “Do you accept the challenge?” Following that, more moments have been painted in my mind and will never fade! I am grateful to Ian Jackson, Caroline M. Eakin, and Andrew Valentine, who are my Ph.D. supervision panelists. Throughout my Ph.D., they always help me reflect on what I have been doing with insightful comments and suggestions. Talking with them can be like finding simple and quick answers on a search engine, or more often like being immersed in the great ocean of knowledge! Also, I feel fortunate to have had great mentors at different stages before my Ph.D.: Liangbao Zhu, Yi Xu, Sidao Ni, and Zhiwei Li. Thank you for your guidance, help, and witness over my growth and transition from a freshman to a researcher! Finally, I would like to thank Thanh-Son Phạm, Thuany Costa de Lima, and Xiaolong Ma, my “Ph.D. colleagues” on similar research topics. My research significantly benefits from their studies and the discussions, conversations, and even debates with them! Thank you! —Sheng Wang, Australian National University, Canberra, A.C.T.