By Distinguished Research Professor Mark Harrison
Professor An Yin, Distinguished Professor of Earth, Planetary, and Space Sciences, passed away suddenly on July 12, 2023 while instructing undergraduate field camp in the White Mountains of eastern California. He is survived by wife Sandy and children Daniel and Hanah. An had a luminous and jocular persona beneath which lay an extraordinarily incisive and original mind.
Born in Harbin, Manchuria, in 1959 during the Great Chinese Famine, he was originally named Jisheng, or “helped by others”, in recognition of a neighbor’s prenatal supplements to his mother’s meager rations. The state subsequently demanded that his name be changed. An grew up during the Cultural Revolution, which provided him with both a social model to react against and the motivation to pursue a career in science.
Indeed, his openness to new ideas and resistance to groupthink coupled with his remarkable intellect made him one of the great geologists of his generation. After excelling in the nationwide university entrance exam, An studied Geomechanics at Beijing University. He graduated in 1982 and joined the M.S. program in structural geology at the University of Southern California. His promise was quickly recognized by Prof. Gregory Davis and he was advanced to the Ph.D. program under Greg’s supervision. Before graduating he was offered a tenure-track faculty position in what is now the Department of Earth, Planetary and Space Sciences at the University of California, Los Angeles where he remained for the rest of his career.
Initially appointed in 1987 as Acting Assistant Professor pending his Ph.D. defense, by 1996 he had ascended to Full Professor and was made Distinguished Professor last year. He shared a joint appointment with the Institute of Geophysics and Planetary Physics from 1995 to 2011.
Professor Yin made profound contributions to understanding how planetary lithospheres form and deform by integrating an unusually broad range of geological and geophysical observations into rigorous interpretations of heretofore unexplained features. He began his career applying elasticity theory to the formation of low-angle faults before migrating to the Indo-Asian collision zone where he developed the tectonic reconstruction for the continent that has been the starting point of research there for over a quarter century.
He took advantage of the opening of Tibet to undertake a vast range of studies that discovered a multitude of geologic and tectonic phenomena, establishing him as the single greatest authority on the Indo- Asian collision. While the principal scientific focus on that continental collision zone has been the dramatic Tibetan and Himalayan topography, its distal effects have resulted in far more earthquake-related deaths.
Returning to his former home of Tianjin, An documented a 160-km-long seismic gap that has not ruptured in over 8,000 years and is capable of generating a similar magnitude quake to that in nearby Tangshan that killed more than a quarter million people. Upon the recognition of slow earthquakes, he developed a diffusion-induced pressure-wave model that, for the first time, relates slow earthquakes to tectonic tremor propagation.
Over the past decade, he investigated extraterrestrial tectonic processes leading to the provocative proposal that Mars had once experienced localized plate tectonics and explaining the origin of the tiger-stripe fractures on Saturn’s moon Enceladus. His scientific influence is documented by both the citation metrics (>38,000 citations; H = 83) of his 200+ published papers and award of the highest honors in the field, including the Penrose and Donath medals of the Geological Society of America.
Equal to his remarkable record of research contributions is Professor Yin’s role as supervisor of nearly 40 graduate theses, undertaken by a remarkably diverse range of students. Eleven of them have gone on to professorships (mostly at R1 universities) and one of his PhD graduates is a NASA astronaut selected to the Artemis lunar lander team. An was a mesmerizing and inspirational undergraduate teacher and the backbone of the UCLA field research curriculum for over 30 years.
He was unstintingly generous in support of his scientific community through numerous editorships and organization of international activities. His meteoric ascent to tectonics stardom made him a global magnet for young scientists from emerging nations. Over 40 visiting scholars from China, India, Taiwan, Mongolia, Turkey, and Iran came to UCLA to learn from the master and left as apostles of An’s credo (borrowed from a TV commercial): Just do it! That is, no excuses; just hard work, astringent logic, and a skepticism of intellectual authority.
Beneath An’s jovial and rational exterior was a deeply emotional and ardent human being who wore the love of his children and geology on his sleeve. He was reflexively impatient with diktat and many a university administrator have glimpsed the side of him forged in the chaos of the Cultural Revolution. The sudden loss of this intellectual giant will be felt acutely across the geologic world mitigated only by the model he left us of how the combination of intellectual rigor, originality, and passion can lead to new insights into how planets work.
Below is a translation to mandarin by Lingsen Meng:
悼念地质学巨匠尹安（享年64岁）
尹安，地球、行星和空间科学系杰出教授，于2023年7月12日辞世，享年64岁。
尹安于1988年在南加州大学获得博士学位。并于1987年在等待博士论文答辩的过程中就正式加入加州大学洛杉矶分校。作为当代最伟大的地质学家之一，尹安对我们的地球有着深远的贡献，并是全球对于印度-亚洲碰撞（形成喜马拉雅山脉和青藏高原的地质事件）领域最权威的专家。
“我们整个地学界都遭受了巨大的损失，”加州大学洛杉矶分校地球、行星和空间科学系杰出教授马克·哈里森（Mark Harrison）表示，“尹教授有着积极和幽默的个性，以及非常敏锐和原创的思维。”
在他许多重要成就中，包括记录了一处地震活动空白地带(seismic gap)，其能够产生与附近唐山地震相似的大地震，后者在1976年夺去了超过二十五万人的生命。他还提出了一种新颖的模型，将缓慢地震（slow earthquake）与构造震颤(tectonic tremor)的传播联系起来。
最近，尹安将自己的专业知识应用于研究太阳系中其他天体上的构造过程。他的研究推断出火星曾经经历过局部的板块构造，并帮助解释了土卫六（Enceladus, 土星的一颗卫星）上著名的虎纹条纹的起源。尹安拥有超过38,000次引用，发表了200多篇论文，并获得了最高荣誉奖项，他的科学影响力不可低估。
与其卓越的研究贡献同样受人称赞的是尹安作为导师、教师和指导者的作用。他的近40名研究生中的11名已成为教授，另有一位是美国国家航天局（NASA）宇航员，并被选入阿尔忒弥斯登月计划团队。尹安特别受到新一代中国科学家的崇敬，其中许多人认为他是中国有史以来培养的最重要的地质学家。
“当我还是学生的时候，尹安就已经是我敬仰的最伟大的地质学家。后来有幸成为系里的一名教授，我才意识到他是多么平易近人、真诚和热情。他热爱与年轻科学家合作扶持我们的工作，我会深深地怀念他，”倪鹏教授表示。
事实上，尹安对全球年轻科学家有着巨大的吸引力。超过40名国际访问学者来到加州大学洛杉矶分校向他学习，并且成为他的世界观的传教士：没有借口，只有努力工作，严谨的逻辑，以及对知识权威的健康怀疑。
尹安还是一位充满激情的本科课程教师，并且在过去30年里一直是加州大学洛杉矶分校地质学领域实地研究课程的中坚力量。尽管地位崇高，但他喜欢的事物中很少有比带领本科生进入野外实习更让他高兴的。
“尹安教授激励我成为一名构造地质学家。他对于本科生群体来说是一个伟大的导师和教育家。他灌输给我严格的工作态度，并培养了我今天在研究生阶段所使用的创造性思维，”前加州大学洛杉矶分校本科生、现为内华达州立大学瑞诺分校 （UNR）研究生的泰瑞·李（Terry Lee）表示。
在尹安欢乐和理性的外表下，是一个情感深沉和热情洋溢的人。“这位科学巨匠的突然离世将在地质界引起强烈的震动，唯一能减轻这种遗憾的是他给我们留下的模范。他展示了如何用严谨的思维、独创性和激情对行星科学产生新的见解，”哈里森说。
