State University of New York
Lianxing Wen was awarded the Macelwane Medal at the AGU Fall Meeting Honors Ceremony, which was held on 10 December 2003, in San Francisco, California. The medal honors “significant contributions to the geophysical sciences by a young scientist of outstanding ability.”
Citation
“In April of 1968, over one million babies were born in China. Lianxing Wen was one of them, and based on his early academic record, he was probably the smartest. He won the National Mathematics Competition at the age of 13, which allowed him to enter college early. He graduated from the University of Science and Technology of China at the top of his class before he was 20, and somewhere along the way, he developed a Richard Feynman grin.
“Lianxing’s talents and diversity of interest are well represented in his first 20 papers, ranging from theoretical seismology to the development of geodynamic models containing three–dimensional viscosity. Many scientists are slowed down by overspecialization and are not broad enough to make major discoveries. Lianxing excels in all those fields, and combines theory and data of all types into a meaningful interpretation of what is inside the Earth. He has targeted three major problems concerning the deep Earth: mantle convection, nature of the core–mantle transition, and the fine structure at the top of the inner core.
“To understand the configuration of the Earth’s convection, he has conducted a thorough assessment of tomographic images containing patterns of cratonic roots, down–welling slabs, and upwelling hotspots. His models demonstrate rather forcefully that simple whole–mantle convection does not work and that it must be broken up into smaller–scale regional convection. To sharpen tomographic images, he addressed the issue of waveform modeling and found that tomographic or one–dimensional–like models cannot explain the rapid variations observed from broadband arrays. To treat this waveform data, he introduced new modeling tools containing a mixture of analytical and numerical codes. Essentially, where the Earth is simple (PREM–like), he uses relatively fast propagating analytical approximations, and where it is complex he resorts to full–numerical methods. This modeling effort led him to examine the African Array data that were collected for upper mantle studies. While the upper mantle data did not produce much excitement, the lower mantle data revealed extreme travel time jumps in the near vertically traveling SKS phases and delays of Sdiff by over 20 seconds. The Pdiff waveforms, along nearly identical paths, appear PREM–like or normal. Lianxing argues that such extreme changes in bulk velocity characteristics along with suggested density anomalies strongly support chemical heterogeneity. He proposes a broad chemically distinct structure at the core–mantle boundary extending from beneath the mid–Atlantic (Cape Verde) to the Indian Ocean (Kerguelen). The implications of his discovery on convection and the genesis of the African superstructure are being widely explored by him and others.
“Lianxing Wen’s work on the outer–inner core boundary is similarly provocative. These studies are mostly observational, but unprecedented in completeness and detail. He argues that there is a regional dependence between PKIKP and PKiKP which can be interpreted in terms of a laterally varying inner core where velocity anomalies mimic those at the core–mantle boundary. This has implications on how the dynamo works, so don’t be surprised to see his next paper on this subject.
“For these contributions, Lianxing Wen is most deserving of this medal.”
—GEORGE V. HELMBERGER, California Institute of Technology, Pasadena
Response
“Thank you, Don, for your generous citation. I am deeply grateful to the American Geophysical Union for this award. It is a great honor to accept this recognition and to have the opportunity to thank those responsible for my standing up here.
“My fortune started when I went to the University of Science and Technology of China (USTC) for my undergraduate study. At USTC, I was surrounded by remarkably talented classmates and a dedicated faculty. I received my basic training in physics and mathematics, and I learned what are needed for becoming a good scientist: self–confidence, persistence, and dedication.
“I was first captured into seismology by Zhenxing Yao, when I moved to the Chinese Academy of Sciences (CAS). Professor Yao inspired me with exciting seismology projects and eventually introduced me to Caltech. At CAS, Tianyu Zheng provided me advice and encouragement, and gave me generously financial assistance for my trip to Caltech.
“At Caltech, Don Helmberger and Don Anderson profoundly influenced my thinking and the way I do science. I thank Don Helmberger for the opportunity to work with him. Indeed, it is my pleasure to honor the Helmberger scientific family with this fourth Macelwane Medal. Don taught me the beauty of deciphering every wiggle of seismograms, and I was inspired by the biweekly meetings with Don, Michael Gurnis, and their students. Having the privilege to work with Don Anderson significantly expanded my horizons. I started with a small class project with him, quantifying the volume of materials that have been subducted in the past 130 million years, and went on to mantle convection problems. Don encouraged my interest in many subjects, among them the geochemical ‘DUPAL’ anomaly, which I later noticed geographically correlates with the compositional anomaly near the core–mantle boundary.
“On a postdoctoral fellowship, I arrived at the Carnegie Institution of Washington (CIW), at a time when the Kaapvaal seismic group just acquired a large amount of seismic data in southern Africa. The Kaapvaal seismic group generously made the seismic data available to me before it was officially released. I thank Sean Solomon for his care, encouragement, and guidance, and I thank Paul Silver for patiently explaining his different views and for his friendship. At CIW, I was fortunate to reunite and collaborate with my best friend, my USTC classmate Fenglin Niu, and I wish to recognize him here for his insights and friendship.
“Stony Brook provides me an intellectual playground. I owe my colleagues a debt of gratitude for such a collegiate and supportive environment where I can concentrate on my research and teaching. Bill Holt has been a great mentor and collaborator and he and Troy Rasbury have been good friends to my family. Don Weidner, Bob Liebermann, Teng–fong Wong, Dan Davis, Scott McLennan, and my students expand my horizons.
“I could not have succeeded, though, without my family. My lovely wife, Mei–Lan Yeh, endures my long working hours and cheers me up in stressful moments. My 4–year–old son Kevin keeps me laughing and renews my energy. It is their love that makes this occasion possible.
“Finally, I thank all of you for being my inspiring peers and for sharing this moment with me.”
—LIANXING WEN, State University of New York, Stony Brook