Stewart Smith (PhD '61), Seismologist

With Hugo Benioff as his advisor, Charles Richter still active, and Frank Press as director, Stewart Smith's memories are a living link to the foundational years of the Seismo Lab. Smith was witness to, and active participant in, the key issues animating the Seismo Lab in the late 1950s and early 1960s. Computers had just achieved a level of sophistication to be put to use in the analysis of seismic waves, and with this advance, the Seismo Lab was focused on understanding the structure of the Earth. And with the Cold War in full swing, the Seismo Lab lent its expertise to detecting and analyzing nuclear explosions - and to discriminate these events from earthquakes.

Working during this formative era, for his thesis, Smith focused on the fundamentals: what is happening in the deep structure of the Earth during an earthquake? The order of the day, then as now, was modeling to help answer these questions. His discovery of a split in the spectral lines, and their relation to vibrational modes, was one of the most significant findings during this period, and Smith credits his mentors and the Lab's singular pursuit of the most basic questions as central to his achievement.

Smith joined the faculty at Caltech directly after defending his thesis, and he remained at Caltech through the 1960s before taking a position at the University of Washington. Over the course of his career, Smith has pursued research topics that run the gamut of seismology, which include his work on great earthquakes, seismic cycles, and source parameters.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Monday, August 1, 2022. I am delighted to be here with Professor Stewart W. Smith. Stewart, it's great to be with you. Thank you for joining me today.

STEWART SMITH: Happy to.

ZIERLER: To start, would you please tell me your current or most recent title and institutional affiliation?

SMITH: I retired from the University of Washington in Seattle. I was in the Department of Earth and Space Sciences, a long time ago now. I retired fairly early; it must have been 1998.

ZIERLER: Have you been active at all in retirement? Are you staying on top of the literature and doing any research yourself?

SMITH: In the first decade I was very active. The internet was very helpful in doing research. At that point, I was collaborating with people at Berkeley, La Jolla, and primarily, USC. I wrote several papers during that period of time. I worked out of my home and the internet made interaction really quite easy; I enjoyed that a lot. I was not ready to give up research when I retired. I was just ready to give up university administration and some aspects of teaching. I'm 90 now and now no longer involved in seismological research. In recent years my interest has moved toward physics. I'm not able to do research in that area, but I am really enjoying reading in that area which has seen such amazing developments since I was a student in Physic back in the 50's.

ZIERLER: Certainly. At a high level, tell me about some of the broad areas in geophysics and seismology that you have worked in over the course of your career.

SMITH: I did some early work with Hugo Benioff on Earth tides. That led to being in the right place at the right time when the Great Chile earthquake occurred and excited the Earth's free oscillations. That basically made my career. Early on at Caltech I continued my research on free oscillations and also worked in several other areas including the detection of underground nuclear explosions, the Parkfield creep/earthquake sequences and the development of a long period digital seismograph and tiltmeter. Later my interest turned more toward earthquake mechanisms and modeling stress release in Southern California. After I moved to the UW in 1970 my interests shifted to volcanic earthquakes at Mt St, Helen and to the Gorda Plate and Mendocino triple junction. Much later an important part of my career was the opportunity serve as President of the Incorporated Research Institutions in Seismology (IRIS).

ZIERLER: Have you been more on the theoretical side or the observational side in your career?

SMITH: Primarily the observational and calculational side. On the theoretical side I benefited from interacting with Charles Archambeau during the time he and I shared Gutenburg's old office at the Seismo Lab.

ZIERLER: What would you say have been some of the biggest surprises in your career, things that were orthodox, understood to be true, that proved to be otherwise?

SMITH: Oh, gosh. The biggest thing that happened during my career at Caltech was the discovery of and exposition of plate tectonics. Plate tectonics did not exist; the understanding of it did not exist when I arrived as a grad student. It was exciting to be in that area. When the picture finally came together it was an amazing to see how the whole tectonic system worked, Magnetic stripes revealing sea floor spreading, subducting plates, transform faults, triple junctions. That was the most exciting thing. Landing a man on the moon, recording moonquakes and starting new exploration of our solar system were also notable events of that time.

ZIERLER: What are some of the technological advances that you have seen in your career? What were some new technologies that came online that really revolutionized the field and what you were able to do?

SMITH: The primary thing would be digital computing enabling large modeling calculations and handling large networks of seismographs. A digital revolution in seismic recording devices was taking place at Caltech, in the petroleum exploration business, and at USGS regional networks. Bob Phinney and myself and along with the engineers at the Seismo Lab developed a long-period digital seismograph using Benioff seismometers. The digital revolution vastly expanded research opportunities throughout geophysics.

ZIERLER: Before Caltech, just to establish some context, where did you do your undergraduate work?

SMITH: I was at MIT as an undergraduate and got my degree there in 1954. I spent a year working for Shell Oil doing seismic exploration in Montana. I was then called to active duty in the Air Force where I worked in flight simulator engineering and later served as a Radar Intercept Controller. After that, I applied to and entered Caltech as a grad student.

ZIERLER: As an undergraduate, were you interested in seismology and geophysics? Is that what you really wanted to pursue in graduate school?

SMITH: Yes. I started off in physics but transferred to Geophysics in my junior year. There were some notable students in geophysics at MIT then. Freeman Gilbert and Bruce Murray among others. Freeman was a year ahead of me and we were roommates my freshman year. He had a huge influence on me. I believe that was one of the big reasons I transferred to geophysics at MIT.

ZIERLER: What kind of advice did you get? What made you think to apply to Caltech for graduate school?

SMITH: I was keeping track of what was going on in geophysics to a certain extent while I was in the Air Force. That was the time when Frank Press was moving from Columbia to Caltech. It was pretty apparent that Caltech was really on the horizon as a central place for seismology in the United States. I was interested in wave propagation and that aspect of seismology, so it seemed like a natural place to go. I applied to several other places, but Caltech was my top priority.

The Mansion

ZIERLER: Tell me about the old Seismo Lab when you arrived in Pasadena in 1957. What was it like there?

SMITH: When I first arrived in 1957 I was assigned as a TA with Gerry Wasserburg on campus. Beginning in winter quarter, I was given a research assistantship with Hugo Benioff. At that point, I began to spend some time at the Seismo Lab. They were just in the transition to Frank Press being the new director. He came there in 1955, I guess, but he was not appointed director until 1957. It was a grand experience. There was this mansion on the hill filled with interesting people. Hugo Benioff was my advisor at that point. Frank Press was director and Charles Richter was still active. Beno Gutenberg was not really active. He was in the office some times, but was not interacting very much with students. But that was the crew—Benioff, Press, and Richter, and an incredibly interesting group of grad students. Frank attracted a bunch of people and there were about half a dozen of us in those days and it was really a tight crew. Anderson, Archambeau, Healy, Harkrider, Ben-Menahem, Alexander, Phinney; it was really a lot of fun. We were a very tight personal group. We had lunch together quite often and our families became friends as well; it was an exciting place to be. We had a number of visiting scientists over the years, Keiiti Aki, and Leon Knopoff among others who contributed greatly to the environment. I believe Kanamori may have had his first contact with the Seismo Lab as a visitor. He became a good friend later and helped me find housing when I went to Tokyo on sabbatical in 1968. Incidentally one of the remarkable experiences at the Lab was the morning coffee break held in the basement, sitting on a bench next to the furnace. Frank was very good at stimulating interesting conversations. I really valued that time, both as a student and later as a faculty member.

ZIERLER: Did you know as a graduate student, at least when you first got there, that these were giants in the field? Was that apparent to you even from the beginning?

SMITH: Yes, it was. It became more apparent as I lived with them.

ZIERLER: Tell me about some of the big ideas in the Seismo Lab when you first arrived. What were the professors debating? What were the big issues in the field at the time?

SMITH: The emphasis was on Earth structure derived from waves, so a broad approach to that from mathematics and computer modeling of waves in the Earth. A central focus was what we called the inverse problem. Given a set of data through waves arriving at seismographs around the world, how do you derive what the waves had passed through, that is, how did the Earth's internal structure influence the wave's properties. Along with that, work focused on understanding and modeling the earthquake source function. The issue of earthquake prediction was always out there beyond reach but occasionally some event or proposal would bring it out.

Harkrider and Press did some of the earliest work on calculating dispersion of waves travelling through the Earth. That was modeling that was just then becoming viable with the computing power that we had. Anderson and others were at the other end figuring out what the structure would be given that data. That was the primary focus, and in my case, it shifted to free oscillations, which is the ultra-long period end of the spectrum. The great Chilean earthquake of 1960, the largest earthquake ever recorded, gave us the first opportunity to look at this part of the spectrum. Benioff had always been interested in free oscillations of the Earth. Early on, I think back as early as the 1950s, there had been a very large earthquake in Kamchatka. It produced a big, long wave. It looked like one and a half cycles of something around an hour in period. He jumped on that and thought that perhaps it was a free oscillation of the Earth because there had been some theoretical calculations showing that the fundamental mode of Earth vibration was likely to be around an hour. Subsequently, it was pretty clear that this apparent disturbance was an artifact, just a transient in the recording apparatus. But he continued to really look hard at it. That was his focus and that developed in an interesting way since it led to him developing instrumentation capable of sensing these ultra long-period waves. Benioff was very broadly interested in waves and did a lot of work in music including design of electronic pianos. He also produced and played an electronic cello, now lost in history. As an aside, I had an interview with fellow who wrote a pretty lengthy and scholarly article about Benioff. Are you aware of that?

ZIERLER: No.

SMITH: His name was Matthias.

ZIERLER: Oh yes.

SMITH: Right. It was published by the University of California Press. It is really long. I learned a lot of things I did not know about his early life. He was also interested in physics and the idea of gravitational waves back in those days. He thought that perhaps the Earth might serve as the antenna for recording gravitational waves. It kind of makes sense. Perturbations in space-time pass through the Earth and produce distortion. That's what strain seismometers do; they measure distortion. He was a good friend of the physicist Joe Weber, then at the University of Maryland, who was doing experiments on vibrations of a giant aluminum cylinder. He was trying to see if gravitational waves could be detected. His experiments ultimately failed, but he and Benioff began discussing the idea of the using the Earth as kind of an antenna to detect gravitational waves.

After the Chilean earthquake, they hopped on that, and together with one of Weber's grad students, Robert Ford, we looked at the background noise level of the Earth vibrations in the spectral range where we had measured free oscillations. Although the gravitational waves discovered by LIGO decades later turned to be far below the threshold we had proposed, and at much higher frequencies than we had assumed, it had been a most interesting diversion from seismology.

It was also quite interesting to work on the underground nuclear detection problem. Minutes or hours layer after a large underground nuclear test the resulting cavity would collapse producing seismic waves somewhat like an earthquake. I did some research in this area that had relevance to the nuclear test discrimination problem, and explained how these collapse events had such different seismic signatures than those of earthquakes or explosions.

ZIERLER: What was the process of determining that Benioff would become your thesis advisor? Did you go around and work with all the others? How did that play out?

SMITH: It happened kind of naturally. I was his research assistant, so I worked on things he wanted me to work on. It started off with Earth tides. Prior to that time, ocean tidal tide analysis, was done with desktop calculators. Digital computers were having an impact in this area. Tides in the solid Earth turn out to be a combined direct effect of the moon and an indirect loading effect in coastal regions produced by the nearby ocean tides. Benioff set me to look at the effects of ocean tide loading and deformation with the idea that the shear stress in the solid Earth produced by ocean tides might be large enough to trigger earthquakes on nearby faults that were already close to a critical state. I was setting up for spectral analysis of his strain data when the great Chilean earthquake occurred so we abandoned the Earth tide project and focused on the global free oscillations that we might find in the data from Chile. A very good idea!

It happened naturally that he became my advisor. I got a lot of advice from Frank Press as well. Benioff was in his later years then, full of ideas still, and a delight to talk with, but I got my mathematical and computer questions advice from Frank. He was in the background, not as a thesis advisor, but he certainly had a big role in my thesis. I should say that there was a certain element of friction in the Seismo Lab in those days. Frank had been appointed in 1957 as director. It was never openly discussed but it was pretty clear that Benioff perhaps thought that was premature. There was some friction apparent but it didn't affect the science. I was Benioff's student, but Frank was a very important ingredient in my thesis and a co-author along with Benioff in the resulting publication.

ZIERLER: Let us start with Benioff first. What was he like as a person?

SMITH: He was charming. [laughs] He was erudite. I did some travel with him in connection with committees such as the Air Force Office of Scientific Research. They were funding Caltech for research in underground detection. I got a chance to see him in kind of a social environment at these various meetings and travel. He had a wonderful sense of humor. He could tell jokes. People at Caltech did not seem to realize that, but I certainly did. He was very humorous and very broadly interested in the sciences and particularly waves of all kinds. He was fun to talk to and there were a lot of really interesting ideas floating around.

ZIERLER: Frank Press, could you tell, just to fast-forward to where his career went, that he was already on that trajectory as early as the late 1950s?

SMITH: Oh, yes.

ZIERLER: In other words, was he already involved in Washington DC, policy, and things like that?

SMITH: Yes, that happened with the onset of the underground nuclear testing and the need to detect and measure the yields of nuclear weapons tested by the Soviet Union, China and others. He was the guiding light in developing a Worldwide Standardized Seismograph Network and that first generation of new instrumentation utilized the Press-Ewing seismometer that he had developed earlier while at Lamont. He was on John Kennedy's Science Advisory Committee in the early 60's, an important time for developing a strategy to monitor Soviet tests. He was clearly a global leader in Seismology as early as 1958 and 1959.

Early Computation

ZIERLER: Tell me about developing your thesis. Let us start first on the technological side. Were there computers even in their very earliest forms that you could work with circa 1959, or 1960?

SMITH: Yes, there were. Caltech had an ancient digital computer. I can still see it now and can remember what it sounded like. I believe it used vacuum tubes. That's how old it was. It was programmed with assembly language and it was slow. David Harkrider at the Lab was the most active user of it from our group. He did the early inversion programs for seismic waves on that computer, which is remarkable because programming the thing was a really huge task. That was also the period of time when IBM sponsored what they called the Western Data Processing Center at UCLA. That was the only major digital computer in the West Coast at that point. It started off I think as an IBM 704, but it was a 709 by the time I got there and the input was by punched cards. A number of us were running our programs at UCLA. We'd laboriously write programs and prepare data cards, then drive down Sunset Boulevard all the way to Westwood because the Hollywood Freeway was not yet completed. We would submit our box of cards written in an early version of Fortran. We never actually saw the computer, we just left the box at the desk and drove back to Pasadena. The runs were overnight, so the next morning we'd drive all the way to Westwood to see the output. A lot of times the output came back and just said, "format error." [laughs] and it had been time wasted. That was quite a hassle.

Frank worked pretty hard to get a computer for us at the Seismo Lab. His story was that the Caltech administration was not going to support computers in departments; they were going to have a computing center. But it wasn't really functioning at that point. To get approval, he had to go through the Caltech central administration. The story, as he tells it any way, was that he probably got it approved when he finally got through to an administrator and found him to be on the golf course instead of at work.

Subsequently, Caltech got an IBM 360 computer and developed a computing center. At that point, we could work on campus. Our Bendix G=15 computer used punched paper tape for input, and the Caltech IBM used punched cards. I ran into interesting people at the Computing Center, particularly late at night. At night we would leave our boxes of cards on the shelf to be processed. Our initials were usually on the box so that we could recognize which belonged to us. We got to know the people there by their initials on the boxes. DGH was Dave Harkrider, DLA was Don Andersson, and SWS was me. Kip Thorne was just Kip.

ZIERLER: Amazing.

SMITH: I sometimes ran into him in the evenings at the computer but never discussed anything of substance with him. I didn't actually realize he was the leader in the early planning for the LIGO experiment. LIGO was of interest to us because it was going to be a really long laser interferometer for measuring distance changes and that's what a strain seismometer does on a very much shorter scale. Frank Press was friends with a number of high officials at Sandia Corporation in New Mexico. They had a big computing center there. He sent David Harkrider and myself there to learn about their spectral analysis programs and run some test data. That was important. Early on, they had the most advanced spectral analysis software and we adopted as much of it as we could.

ZIERLER: I wonder if you might explain—long before online databases and the internet, decades before these advances, how was data shared at a place like the Seismo Lab and was it proprietary to some degree, meaning that scholars from other institutions would physically have to come to the Seismo Lab to access it?

SMITH: Since earliest times, sharing of seismograms by mail between universities was very common. The Jesuits were leaders in this area, and the global reach of their colleges was very important. The earliest seismic recordings some inscribed by tracings on smoked paper were fragile. Later, as photographic recording became standard, data interchange by mail flourished, with the USGS playing an important international role. DARPA had the first digital data exchange going on for its own purposes, so seismology kind of tacked onto that in a natural way because DARPA was funding our research on nuclear detection discrimination. CERN was operating a highly developed system for the international physics community but it wasn't available for others until it finally emerged as the Internet! Before that we had been able to use DARPANET in a limited way to exchange data with certain U.S. universities. There was no center for storing and distributing digital data but we could individually share files with colleagues at Berkeley or UCSD for example. Digital data sharing became more common in the 1970's with the development data bases at the USGS. I had a role in developing the IRIS data center while I was in Washington DC in the early 80's. That and the USGS data center became the primary places for global digital data sharing over the internet.

The Cold War and Nuclear Weapons

ZIERLER: You mentioned DARPA. Do you remember if the Cold War was a big issue for this Seismo Lab, nuclear testing verification and things like that while you were there?

SMITH: Yes, when it was recognized that seismic data had the potential to discriminate underground nuclear tests anywhere in the world, it became a very hot topic at the Lab and throughout the seismological community. With DARPA funding for instrumentation and research it became very important. We were of course fairly close to the Nevada Test Site so our recordings were quite important. The tests were classified. When the detonation was going to take place was a secret, but somehow or another Frank always knew when it would be. When we saw a rope across the bottom of the driveway of the Seismo Lab, we knew that there was going to be test that morning because cars driving into our parking lot would disturb the seismographs in the in the tunnel beneath the building. We didn't want any cars moving in the parking lot when there were tests going on. It was kind of a joke; you would see a rope and a little flag across the driveway and you knew there was going to be a test that day.

It was huge in a number of respects. The research opportunities and the funding were really important, not only for stations in remote areas, but also for the analysis of data. The primary places that were involved were UCSD, Berkeley, Columbia and Caltech. It was really a major effort because in those days, when you looked at a seismogram you couldn't tell if an event had been an earthquake or an underground explosion. For small earthquakes, there were comparable waves but there were subtle differences that you could bring out with large datasets and digital processing. That was a major activity in the 1960s and 1970s. It funded a lot of basic research that ended up being useful in general for earthquake source functions and Earth structure in addition to helping provide the basis for the Test Ban Treaty. The motivation and funding for analysis and instrumentation was for the underground nuclear test program, but the output was just huge for seismology in general.

ZIERLER: Tell me about the culture at the Seismo Lab. Did you feel sort of sequestered off from the rest of campus? Did you feel like you were at Caltech?

SMITH: Yes, I felt like I was at Caltech, and I benefited greatly from that environment. Although there was a small element of separation it fostered great communication and support among all of us. We taught courses on campus, and we had students who spent part of their days on campus and also came to the Lab for. Occasionally at the faculty level you might sense a little competition for funding, but that is natural in an academic setting.

The Structure of the Earth

ZIERLER: What was the process like intellectually of setting up your thesis research? In other words, what were some of the bigger questions in the field at that point? What was the narrow slice of research that you focused on to address some of those broader questions?

SMITH: It was pretty narrow. The idea was that the Earth is a giant elastic ball with some complicated structure inside. If you bang it with a giant hammer, it's going to ring like a bell. The question was, are earthquakes a big enough hammer to make the excitations or vibrations large enough that we could measure them.

I would say there weren't any mysteries involved; one of the central questions had to do with the instruments, could they respond to really low frequencies. The Benioff strain seismographs were a substantial improvement over seismometers in this area. The free oscillations of the Earth that produce vertical motion are called spheroidal. The Earth goes back and forth between a football shape and a flattened sphere. There are also torsional rotations where the Earth strains in a shear fashion. It turns out the strain seismometers were the only instruments that were very sensitive to that kind of deformation. There was a lot of interest in trying to detect and isolate these so-called torsional oscillations from the spheroidal. It was an interesting problem. We managed to make the first measurements of the torsional modes as well. What was the rest of your question here?

ZIERLER: Just the big questions in the field and how you saw your thesis research being responsive to them.

SMITH: The big questions were, what is the structure of the Earth, and for seismology in particular, a really huge question was what goes on during an earthquake. It is some kind of rupture over very large distances where a big chunk of the Earth slides, the plates are moving, and so forth. The way we addressed that was by modeling. We would make a mathematical models to investigate how a rupture might initiate, propagate, and stop. The seismic waves generated during these three different phases of rupture are quite different. That was basically another inverse problem and would try to work backward from the data we saw to what actually happened at the earthquake's source.

That, and Earth's structure, were central problems in seismology. The idea of discriminating between an earthquake and a nuclear explosion, that was an important technical detail, but not a fundamental problem. The earthquake source problem is still not fully understood. More importantly, is there anything we can measure ahead of time that tells us when it's likely to rupture. The answer, as of now, is "no" [laughs] but people have not given up on the problem.

ZIERLER: What were some of the theories in the field at the time that might have provided some intellectual guidance for what the data was telling you?

SMITH: Models for the earthquake process were primarily coming from rupture theory and out of the laboratory, where people were looking in great detail at the rupture initiation and propagation. That is not my area of expertise but there were lots of models that could be tested. There are a variety of different properties of rocks that you can only get by measurements in a laboratory. There is an element of viscosity and the effects of temperature and pressure on ruptures that varies with depth. That can have a big effect on the models of how a rupture might initiate and propagate.

ZIERLER: Did your thesis research have a lot of field work involved?

SMITH: No, it was all computer work. A big part of it was reducing the paper records from ink chart or photographic recordings—the wiggly lines—reducing those to digits, very large amounts of them. As an aside, the Benioff strainmeters produced a strip chart records that were fairly easy to digitize but for the Chilean earthquake, which required a week's recording could be as long as 30 ft. The rest of the seismographs in our network at that time were daily photographic recordings made on a rotating drum. For most seismograph analysis it was easy to measure the time of arrival of specific wave packets, but for spectral analysis long recording are necessary. This meant many rotations of the recording drum and the potential tangling of the traces.

SMITH: There is still to this day, I believe, displayed in the office of the Division, an example of one of my tracings of a tangled record from the Chilean earthquake.

ZIERLER: When you had a question, would you be more likely to go to Benioff or Press or would it depend on what the question was?

SMITH: My questions generally had to do with calibration and frequency response of the instruments. Benioff was right on top of that. For computers or analysis, Frank was my primary go-to person. The other grad students were a really important resource as well. We were a tight group and we helped each other.

ZIERLER: When did you know you had enough to defend? When did it feel like it was a complete project?

SMITH: Early on I had the results on three or four of the fundamental modes of the Earth which were the most interesting. I had that in the summer of 1960, I guess, and Press was going to conference in Europe. Oh, it was the International Union of Geodesy and Geophysics, IUGG meeting, and he was there while my results were just starting to come out of the computer. I was sending daily telegrams about the spectra to Frank in Helsinki where he was reporting it to the world. I knew right then that this was the thesis.

ZIERLER: Who was at your defense besides of course Benioff and Press?

SMITH: Oh, that's interesting. [laughs] Clarence Allen and Gerry Wasserburg from the Division, and because I had a minor in Mathematics, John Todd from Mathematics. He was an abstract mathematician. Luckily, he didn't bring up any abstract mathematics; he just sat and listened and thought it was interesting. William Smythe from Physics was also on the committee. Have you ever heard the name Smythe?

ZIERLER: Yes!

SMITH: A fearsome course, a yearlong course in high-intensity electromagnetic theory. God, that's the hardest course I ever took in my life. He came to the exam and was silent. He didn't ask me any questions. I was so thankful. I thought I'd be at the blackboard and he might say "How about you do a conformal transformation of this equation?" Anyway, he was thankfully very silent. They were very interested. Everybody was interested. This was exciting stuff. There was one other member from Geology; but I can't recall who it was now.

ZIERLER: What were some of the big conclusions or contributions of your thesis, looking back?

SMITH: These spectral line frequencies and their associated modes of vibration were major discoveries. They were vital in determining the properties of the Earth's deep interior. They provided important constraints on all Earth structure models. The most surprising thing to me was the discovery that the fundamental mode of the Earth, instead of being a single line in the spectrum, was split into two or three lines. The splitting of spectral lines is very common in physics and it plays an essential role in spectroscopy and the properties of atoms. A magnetic field, for example, can split the spectrum of an atom. In the case of the Earth, its daily rotation and oblateness was responsible for the splitting.

George Backus at UCSD saw our result and was able to mathematically confirm that the rotation of Earth was the cause. That we could actually measure this effect was, I thought, quite extraordinary. Also, it turned out to provide an additional constraint on the models that were developing for deep structure.

We also detected radial modes of oscillation. It's somewhat puzzling that earthquakes are so effective in exciting this type of motion. Since the attenuation of compressional deformation is less than that of shear deformation, these radial modes ring longer. The spheroidal and toroidal oscillations die out over a period of hours but the radial ones may go on for days. It was a big surprise that a couple of weeks after the earthquake we could still detect the radial modes with an oscillation period of 20 minutes or so. That was really pretty interesting. Once the digitizing and programming was complete, a lot of experimentation with filtering and other parameters was still necessary. Finally. it was quite exciting to watch the spectral results come out. No one else had ever seen these properties of Earth before. I had a profound feeling of discovery.

ZIERLER: After you defended, what opportunities were available to you? What did you want to do next?

SMITH: I wanted to continue to work in that area with the kind of data that was available at Caltech. Caltech was high on my list though I thought it might be out of the question. It's somewhat unusual for graduate students to continue on the faculty at Caltech, so I had kind of ruled out that possibility.

ZIERLER: What about as a postdoc?

SMITH: I was more interested in a more permanent position. I would have considered it but I was looking for other opportunities. I was in contact with people at UCSD in San Diego, Walter Munk, and I think he was prepared to—as a matter of fact, they did make a job offer. I also had an offer from Stanford. When Bob Sharp and Frank Press came up with an offer as Assistant Professor at Caltech, beyond my expectations, I grabbed it.

From Caltech to UW Faculty

ZIERLER: What was the offer initially?

SMITH: I think it was $6,500 a year. While I had been a grad student, my wife, Nancy, had supported me, she was teaching in the Pasadena school system. Then we had three children in a row, [laughs], so it was helpful to have a salary. We could live on $6,500 a year. [laughs]

ZIERLER: What ultimately did you decide?

SMITH: Oh, I instantaneously accepted it.

ZIERLER: What was your title?

SMITH: Assistant Professor.

ZIERLER: It was a tenure track position?

SMITH: Yes. It was a bit unusual that Frank managed to get two new faculty appointments that year, Bob Phinney and myself. Bob stayed on for a couple of years and then left for Princeton. He was one of my close colleagues and was a real expert in complex digital computing. He was a leader in the digital seismograph operation we set up at the Lab. I missed him when he left. When he left Don Anderson had just completed his thesis and was clearly at the forefront in his field of Earth Structure and was appointed to the open position.

ZIERLER: What aspects when you joined the faculty did you want to continue from your thesis research and where was there opportunity for new lines of inquiry?

SMITH: At that point it's basically up to the individual faculty members to decide because there is not much central funding out of the administration for research, so, to do research you have to have proposals and you have to get them funded by the National Science Foundations or the USGS and so forth. I wrote some proposals continuing my work on free oscillations and Earth tides. A major part was trying to measure Q (attenuation)—it's a number that describes how rapidly an oscillating system will die away. It's really important for getting at the structure of the material. I wrote some proposals to measure Q from the free oscillation data. I wrote some proposals to DARPA and NSF for earthquake source analysis which would fundamentally try to derive the properties of the source from the seismic waves. It had some applications to underground explosions as well as rupture on an earthquake fault.

ZIERLER: Did you take on your own graduate students at that point?

SMITH: Yes. I was able to fund graduate students. One of them was Charles Sammis. We continued our interaction over the years. Many years later, after I had retired and he was on the faculty at USC, we resumed our work together and he became one of my primary collaborators on several papers concerning computer modeling of earthquake sources and triggering of earthquakes by solid Earth tides. I had some other students that went on to faculty positions, Francis Wu, he's probably retired now from Stony Brook, and Leon Teng at UCSD, and several who went into industry. One of my students did a thesis on stress distribution during earthquakes but then went on to work in his father's company in an unrelated area [laughs]. I had productive interactions with visiting faculty post docs over the years, including Max Wyss and K. Kasahara.

ZIERLER: Ultimately how long did you stay at Caltech?

SMITH: Nine years, I was appointed in 1961, promoted to Associate Professor around 1966 and did a sabbatical at Tokyo University back in 1969. I got an inquiry from the University of Washington while I was in Tokyo about coming up to chair a new department. Since I grew up in Seattle I was really interested, I wrote back and said, "I'll come for an interview, I'll come over from Tokyo." They said, "No, no, don't bother. We'll wait until you get back next summer." My heart was in this area. When we were graduate students we would sometimes sit around in the evening at the Seismo Lab and discuss places we would like to live after we graduated and got jobs. It was really interesting, [laughs] everybody was focusing back on where they grew up. Archambeau wanted to go back to northern Minnesota, Bob Phinney yearned to return to the east coast, and I wanted to go to Seattle. I don't recall Don wanting to go back to Baltimore. Anyway, everybody had a special place, and none of us favored Los Angeles.

ZIERLER: You're from Seattle?

SMITH: Yes. I grew up here, so when I got the job offer, I took it. Also, it was a real challenge. It was really interesting because it was basically the start of a new graduate program in geophysics

ZIERLER: You mentioned you were part of the process of creating a new program entirely.

SMITH: Yes, it was new interdisciplinary graduate department including joint appointments with Physics, Geology, Atmospheric Science, Oceanography and Civil Engineering. In addition to my appointment, I was given four additional full time faculty appointments to make. We were to be in the Graduate School here rather than in the College of Arts and Sciences. Many of our faculty were shared with other departments. We were an interdisciplinary group. In the first year I was able to a recruit marine geophysicist from Wisconsin, rock mechanics experimentalist from UCLA, a global dynamics theoretician from Stanford, and a space scientist from UC Berkeley. It was a great opportunity, we had a nice group going that also involved interested faculty from Physics, Oceanography, Geology, Glaciology, and Civil Engineering. We eventually merged with the Geology Department, and it's now called the Department of Earth and Space Sciences. The Administration recently moved it to the new College of Environmental Sciences. The Department is doing very well and I'm proud to have played a role in its inception.

ZIERLER: Your responsibility was to build up the seismology component?

SMITH: No. We already had one seismologist joining us from Geology, myself, and a postdoc from Nevada, so with an existing seismic network in the NW, we were already viable. My responsibility was to make this a strong interdisciplinary group that could gain national recognition. Demonstrably that turned out to be true.

ZIERLER: What were some of the funding sources at UW that made this expansion possible?

SMITH: The UW was awarded a special NSF University Science Development Grant that included the development of a new graduate department in Geophysics. It was a very big grant, including a new building with extensive laboratories, and it provided four new full-time faculty appointments. It was a big commitment on UW's part as well. Deans in the College of Arts and Sciences and the Graduate School at the time were very supportive. There were several key faculty in existing geology, oceanography, physics, and glaciology departments that were driving this and they were critical in achieving its success.

ZIERLER: Did this new endeavor change your research at all, the kinds of things you were interested in?

SMITH: Yes, In the early years the administrative and management load was such I was able to keep only one small research program going. I was chair for 10 years and it turned out the tradition in Arts and Sciences was to switch chairs every five years but somehow it never happened. I finally brought it up after 10 years and said, "I don't want to do this anymore." [laughs] So, I was then able to focus on my research program with the network in Northern California concerning the Mendocino Triple Junction. That was my primary activity in the late 70's and early 80's. I was out administration and management at the UW, but later ended up with even more of it with IRIS.

I took off and did some new things after I retired, including earthquake source modeling with Sammis at UCSD which was really interesting and resulted in a couple of publications.

ZIERLER: You were part of the establishment of IRIS?

SMITH: Yes.

ZIERLER: How did that come together? What were some of the key interests that made that happen?

SMITH: There were 2 objectives for the IRIS program, The Global Seismic Network (GSN) and the Portable Array Seismic Studies of the Continental Lithosphere (PASSCAL)

The existing global network was ancient, by technology standards. It was put in with Frank Press's push back in the 1960s. By the time the 1970s arrived, there was a whole new generation of seismographic instruments that were much more sensitive, much broader band, and digital recording. We needed to upgrade the entire global network and USGS didn't have the funding to do it, but DARPA did. They were interested in more seismographs particularly in the Soviet Union and China. Word kind of spread that there was an opportunity here and a key group of people from Columbia (Lamont), Berkeley, Caltech, UCLA, Stanford, Harvard, Wisconsin, Princeton, Washington (me), and UCSD formed a committee see what we could do to get NSF funding to establish a global network. The committee, chaired by Tom McEvilly from Berkeley. decided we really had to have a full-time staff and a central headquarters, probably in Washington DC in order for the program to succeed. We went home from that meeting to think about who might lead that effort. It didn't occur to me to do it because I was quite happy here at the UW, but the committee did a search and ultimately asked me to do it. I thought it was an interesting opportunity and said I would if I could get a leave of absence from the UW. The Dean approved leave of absence for two years initially and subsequently for two more.

I moved back to Washington DC in the summer of 1985 and rented office space in Rosslyn across the Potomac. Laptops didn't exist then, so I took my big box computer, set it up on the floor in this empty office with a chair [laughs], and started hiring people and working on the proposal for the subsequent year to fund all this. A small subset of our original committee, the IRIS Executive Committee was formed to provide continuing oversight. They met once a month with me in Washington and took a central role in writing our large NSF grant for the following years. It included Freeman Gilbert from UCSD, Adam Dziewanski from Harvard, Don Anderson from Caltech and Tom McEvilly from Berkeley. The other key names are fading in my mind. Anyway! All of these people were actively involved in writing the initial proposal. Things were going very well and they asked me to stay on after my two year appointment. When I left in1989 my old colleague Bob Phinney then at Princeton took the helm for a year until a permanent president could be found. I worked pretty hard search and we was really pleased when David Simpson from Columbia (Lamont) agreed to take the position as President in 1990. He served extremely in that office for the next 23 years. Thank you, David. IRIS moved its central offices from Rosslyn to downtown DC in the early1990's with the IRIS Data Center then located near the University of Washington and the PASSCAL Instrument Center at New Mexico Tech. Overall the IRIS program has been a remarkable success over these past 27 years and I'm proud to have had an early role in its birth.

ZIERLER: Did you stay involved with IRIS after its founding?

SMITH: Yes, after 4 years as President when I returned to the UW I chaired the IRIS committee concerned with establishing stations is Russia and China I eventually drifted out of it, maybe partly because it was awkward to transition from chief executive officer to a committee chairman who could only suggest things [laughs]. I was quite happy here at the UW finishing and publishing my work on the Gorda Plate and the Mendocino triple junction,

ZIERLER: Now that we've made it up to retirement, for the last part of our talk, I want to ask a few broadly retrospective questions, and then we will end looking to the future. First, have you kept up with the Seismo Lab over the years? Were you in contact with your former colleagues, paid attention to what was happening?

SMITH: Yes, the ones at Caltech, Don Anderson, David Harkrider, Clarence Allen, Barclay Kamb, Gerry Wasserburg, Bob Kovach, Charlie Sammis, Bruce Julian, and Wayne Thatcher were personal friends that stayed in touch. Oh, I did a brief sabbatical at Caltech around 1979. It was good to see how the Seismo Lab was integrating with the GPS Division. Great to see that the coffee break in the furnace room tradition survived. After retiring I taught part-time at the UW for a couple of years, but time went on I began to lose contacts there. In retirement over that next decade I continued independent research project at home and over the internet including some with Charlie Sammis at USC that produced several publications. In the very last decade, when I was in my 80's, my principal focus became caregiver for Nancy, my beloved but now departed wife of 65 years.

ZIERLER: What unique perspective might you have on the Seismo Lab being both a graduate student and a faculty member there that others might not who have only been one or the other?

SMITH: I am not sure if there is any. [laughs] When the old guard was gone—Gutenberg died, Richter disappeared—he was still around—Benioff and Press were the principal faculty focus. And then over time with new faculty and changes in both technology and in the science of seismology the Lab transitioned to its current state—now years and years later, it seems everybody I had known was gone except for Clarence and Hiroo, and now I see that Clarence has passed away as well. I am not sure I have any insight into what you ask. It just seems like a natural evolution. There is no lesson in it other than that powerful, intense, brilliant people affect the environment throughout, and that environment changes.

ZIERLER: I am sure that you heard this idea before that five or six decades ago, in seismology, the Seismo Lab felt like the center of the world. Today it is a much different situation. How much of that do you think is about the Seismo Lab itself and how much of it is about simply the way the field has grown and the way that data is available worldwide?

SMITH: It is probably all of the above, but I would guess an important feature was the integration of the seismological operation with the Division. They are still leaders in the field. Other groups have developed, but I can see as an outside observer, almost like the public looking in, that the kinds of things going on at Caltech in seismology today are pretty amazing. Using the existing underground fiber optics networks as a means to sense earthquakes? Really? The Seismo Lab was a wonderful environment. I absolutely loved it, and the environment on campus as well. Both were my home. Who can forget seeing their 4-year old daughter sitting on Santa's (Feynman's) lap at the Faculty Christmas Party in the Atheneum? The Old Seismo Lab. Maybe at the time, it was just the right kind of environment to flourish. Now it has adapted to a new environment.

ZIERLER: Either from your time as a graduate student or on the faculty at the Seismo Lab, what has stayed with you ever since, in terms of collaborations, approach to the research, focusing on the big questions in the field?

SMITH: I can't think of specific things. Clearly the experience shaped how I approached the work of science. It also set my expectations and my work habits. Perhaps the biggest change for me when I left Caltech was the increase in management and administrative work. Perhaps until retirement I never got back to the focus on research that I felt that I had at the Seismo Lab. However, there were compensating factors so all in all it was a tradeoff that I was happy to have made. I think in my particular case, it was probably good.

ZIERLER: Between the science and your administrative responsibilities, what do you see as your most significant contributions in your career?

SMITH: I believe the largest long-term impact of my career has been the birth and development of IRIS, and the origination of a Graduate Program in Geophysics at the University of Washington

The experimental work that I did on free oscillations had an extremely large initial impact. It initiated a flurry of publications about Earth structure by leaders in that field of research, culminating in Anderson and Dziewanski's seminal publication (more than 11,000 citations) of a "Standard Model" for the deep interior structure of the Earth.

My early work measuring creep on the San Andreas fault at Parkfield, defining active subduction at Cape Mendocino and volcanic seismicity in the Pacific NW was important and encouraged further work in these areas as more data became available in later years.

ZIERLER: What are some of the big surprises, to the extent that you have kept up with literature, things that are possible now that were not even conceivable back in the 1950s?

SMITH: Oh, wow. I think the back to planetary sciences element of geophysics which was back in the 50s. We were amazed by Sputnik at that point. Now you can remotely measure quakes on the moon, storms on Jupiter, the structure of Mars, or work with actual planetary samples in the lab. Earth and sciences have become quite a big deal. The incredible increase in computing powers, in data processing, in solution of inverse problems and in "deep learning" analysis will continue have profound effects in these areas.

ZIERLER: On that point, looking to the future, if you have the opportunity ever to talk with current graduate students, what are the kinds of things that they're focusing on now that build on the questions that you were involved with 60, 70 years ago?

SMITH: That is hard to say. [Laughs] There are certain kinds of overreaching problems that were with us 60 or 70 years ago, concerning earthquake process. How does it happen? What's driving it? Are there any indications that you can tell when a system is sufficiently unstable or at a. critical point that an earthquake is imminent? Prediction was the driving force for seismology starting in the 1920s and the 1930s. The problem is still out there and it's going to continue to influence where the research goes. I think we'll find out new things, though may never solve the problem of earthquake prediction. Maybe it is insoluble; that's conceivable.

ZIERLER: Meaning that it's not about the instruments. It's not necessarily about the technology. It might be something just fundamentally beyond our reach.

SMITH: Well, perhaps I shouldn't have used the term insoluble since statistical predictions might become precise enough to be "close enough for all practical purposes" as the old joke puts it.

ZIERLER: On that note, it's been a great pleasure spending this time with you, capturing all your historical perspective. I am so glad we were able to do this. Thank you so much.

[END]