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Donald V. Helmberger (1938–2020)
No full textDonald V. Helmberger, Ph.D. and Smits Family Professor of Geophysics Emeritus at Caltech, and one of the most impactful seismologists to have lived, died on 13 August 2020. Don was born 23 January 1938, the youngest child of 13, in the small rural town of Perham, Minnesota. He completed his bachelor’s degree in physics at the University of Minnesota in 1961. That summer, he participated in a cruise involving seismic imaging of the oceanic crust in the Bering Sea and was inspired by the challenge of interpreting the recorded seismic waveforms—the beginning of a lifelong passion. That experience drew him to a new focus on geophysics, and he enrolled in the graduate program at the University of California San Diego, where he completed a master’s degree in 1965 and a Ph.D. in 1967. His graduate work was strongly influenced by Russell Raitt and Freeman Gilbert. After a 2 yr appointment as a research associate at Massachusetts Institute of Technology, working with Frank Press and M. Nafi Toksöz, he joined the faculty for 1 yr at Princeton University. In 1970, Don moved to the Seismological Laboratory at Caltech, where he spent the rest of his career. From 1998 to 2003, he served as Director of the Seismological Laboratory, one of the few intervals in which he let an administrative role divert him from full‐time efforts to understand the wiggles in seismograms. He became emeritus in 2017
Interview with Donald V. Helmberger
Full text linkInterview in two sessions, May and June 1999, with Donald V. Helmberger, Smits Family Professor of Geophysics and Planetary Sciences in the Division of Geological and Planetary Sciences.
He begins by recalling his family background and childhood on a farm in Northern Minnesota, one of thirteen children. Matriculates at the University of Minnesota in 1956 (B.S. 1961). Summer work at Scripps Institution of Oceanography, 1961; sails to Alaska on a research vessel studying the structure of the oceanic crust. Transfers to UCSD for graduate work in geophysics; works at Scripps with Russell Raitt (PhD 1967). Recollections of Walter Munk and Freeman Gilbert. Two-year postdoctoral position at MIT, with Frank Press and Nafi Toksoz; introduced to seismology. Works on upper-mantle modeling, supported by U.S. Air Force in connection with underground testing of nuclear weapons. Becomes an assistant professor at Princeton in 1969; following year, joins Caltech Seismology Laboratory as assistant professor of geophysics. After 1971 San Fernando Earthquake, works on high-frequency modeling of earthquakes.
Recollections of Seismo Lab when it was on N. San Rafael Ave., in Pasadena, and of the move in 1974 to South Mudd, on Caltech campus. Memories of Charles Richter. Recalls students: Charles Langston, Thomas Heaton, Thorne Lay, Terry Wallace, Stephen Grand. Comments on Hiroo Kanamori, director of Seismo Lab 1990-1998. Discusses National Science Foundation's establishment of earthquake centers and hopes for Caltech to get the first one; Caltech loses out to SUNY Buffalo.
Succeeds Kanamori as director of the Seismo Lab in 1998. Discusses evolution of directorship since Don Anderson's tenure (1969-1989) and effects of the move to Caltech campus. Discusses Kanamori's directorship and work on TriNet. Discusses Seismo Lab's relations with U.S. Geological Survey and the CUBE program [Caltech-USGS Broadcast of Earthquakes]. Concludes by discussing his own efforts as director of the Seismo Lab and his hopes for its future
My seismology journey with Donald V. Helmberger
No full textMy journey on the wiggles with Don started from February 2008, when I got an opportunity to visit the Caltech Seismolab as a visiting PhD student, which was made possible via Dr. Sidao Ni’s recommendation. A previous student of Don, Sidao was a professor at the School of Earth and Space Sciences (ESS) at the University of Science and Technology of China (USTC) at that time. Sidao offered the “Computational Seismology” class at USTC where I learned a lot about the modern developments in seismology. I also met Sidao many times to discuss a wide range of research topics, I believe it is a style he inherited from his experiences with Don and other professors in Seismolab.Published versio
Exploring Earth's boundaries with Donald V. Helmberger
No full textSeismic waveform modeling is one of the most powerful tools for understanding Earth’s structure, since it allows waveforms to be quantitatively predicted using physical source representations and a velocity model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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