Bryan Isacks

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Interviewed by
Kai-Henrik Barth
Cornell University, Ithaca, New York
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Interview of Bryan Isacks by Kai-Henrik Barth on 1998 June 9, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA,

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The interview focuses on Isacks' training and career as a seismologist at Columbia University's Lamont Geological Observatory, covering the period before 1970. He reflects on the influence of the Department of Defense's "Project Vela Uniform," which aimed at improving seismic detection capabilities, on his career and more generally on the development of seismology in the 1960s. He also describes his contributions to the Plate Tectonics revolution.


How did Isacks become interested in seismology? Isacks was undergraduate at Columbia, majoring in physics and geology, and he applied for summer job at Lamont, he wanted to go on research vessel VEMA; previous summers he had worked for oil company in Louisiana (Gulf Oil) doing seismic exploration, summer job to earn money; so he applied in his junior year for a job on the VEMA and didn't get it (team was already complete), this was summer of 1957; at the beginning of this summer he received a call from Jack Oliver who had a job, if Isacks wanted it, in the Arctic ocean, and Isacks accepted and flew up to Thule, Greenland, and joined research team on ice-island T3: did meteorology, oceanography, a little ocean bottom seismology; through this project he got connected with Lamont, and the next summer he had another job in the Arctic; Isacks got very interested in geophysics through his contact with Oliver; when he applied to graduate school he applied to various places including Columbia and decided to go to Columbia; he stayed in the Arctic through the fall of 1958 and started grad school in spring of 1959 with Oliver as his research director; because of Oliver, Isacks went into geophysics with concentration in seismology; he says that work with oil company (seismic reflection work) might have predisposed him towards seismology relative to other fields in geophysics he might have gone into, plus the connection with Oliver.

Isacks's work with the oil company in the Louisiana swamps: seismic reflection profiling in the delta region of Louisiana swamps: he worked three summers in that job in variety of capacities: first two summers he was field helper and carrying equipment through the swamps and helping the surveyor, and in third summer he got involved in the interpretation part; the crew stayed on a house boat in the swamps for ten days at a time, data would come every day, make preliminary interpretations, then data sent back to Houston for final interpretations: so he got a fairly broad experience in the field aspects of seismology as well as some of the interpretations; this connected with the courses in geology and geophysics he was taken; he was looking for a job with some technical component to it, and his family knew people who were connected with Gulf Oil, normally those types of jobs are not easy to get, family connection; ideal in a sense because the job involved a lot of physics and a lot of field work (he liked that, was outdoors type, liked working outdoors)

Decision to come to Columbia for his undergraduate and graduate work: mainly two summer jobs working for Lamont and getting to know Jack Oliver and others; on the ice-islands Oliver was not there: second summer he worked with Ken Hunkens (sp??) who was also at Lamont; Columbia seemed like a lot of possibilities; where there other attractive programs at that point? I.: he applied at Berkeley, Caltech, and was accepted; Isacks was not aware at that point of St. Louis, he knew Berkeley and Caltech more by reputation, not specifically for geophysics or seismology

When he began his grad work at Lamont, was he then already focusing on seismology? He was fairly focused on seismology: the seismological research program there was fairly vigorous, a fairly large operation (although not as large as the oceanographic operation): Isacks didn't weigh the pros and cons of the groups, he had made the decision unconsciously to be in Oliver's group; he appreciated the field work opportunities, the group allowed him to tinker with instruments (he enjoyed ever since he was a teenager); he thought it was a good fit and entered the group in spring of 1959; oceanography had a fairly large group at that time because of running the ships and so on; in seismology: total with grad students maybe just ten people: names: Jim Brune, Paul Pomeroy (both ahead of Isacks, they were already grad students then), Jim Dorman (work on Rayleigh waves), George Sutton (was grad student then, got on faculty while !sacks was grad student, became one of Isacks' s faculty advisors), Jack Oliver, Jack Nafe, Marc Landesman (doing work on Love waves), Lynn Sykes came a year after Isacks, Gary Latham (worked later on the Lunar program): about ten people in the late 1950s

[1959 Vela Uniform starts, so Isacks came to Lamont just when big money from Department of Defense begins to flow for studies in seismic detection] Any changes in Lamont program as a consequence of Vela? Isacks saw growth; when Isacks came to Lamont he worked with Oliver (he could have continued the Arctic studies with Ken Hunkins (sp??), but he was more attracted to the seismology work, and also Oliver very charismatic personality, very engaging); Isacks didn't see the beginning of Vela, but Lamont build a new building, moved out of the old Lamont Hall and build the seismology building [important point, because after the move, Maurice Ewing phased out of the seismology work at Lamont]; Isacks: he remembers talking to Ewing, but at that point it was pretty much Jack Oliver's show with Jack Nafe and Jim Brune and Jim Dorman and Marc Landisman; Ewing was there, but not a dominant figure in the seismological work at that point; the early 50s, Ewing and Press dominant; [in the early 60s] Ewing much more interested in the oceanographic work and pretty much gave Oliver control of seismological program of Lamont; Isacks remembers going with [Paul] Pomeroy late 1950s or early 1960s to AGU [American Geophysical Union] meeting and Paul [Pomeroy] said to Isacks that Isacks was really lucky to get in: this is the right time for a graduate student to get into seismology, because they are looking for people and there is lots of money and there is more money than students; at that point one could have a more or less regular job at Lamont and still be a grad student; (later they changed that and you would be a research assistant at a much lower salary level): Isacks: it was a nice way to be a grad student, doing research and basically having a regular salary and also going to courses; they [Lamont?] were really looking for graduate students and trying to build up research capabilities.

Early 1960s: not a huge infusion of new people at Lamont: Lynn Sykes, a larger number came in later on in the mid to late 1960s, about 5-6 years after Isacks started, people like Peter Molnar, M. Barazangi, Bob Page, Peter Ward (Isacks was born in 1936, height of Depression, few babies born then, so not many people of his age available: it was a problem to get students, when he started: demographics; in mid to late 1960s the Baby Boom wave hit the US: then having more graduate students around); when Isacks first started and during the first few years: Sykes, Latham, ahead of Isacks was Pomeroy, Sutton, Dorman (students in seismology); so, not a huge bunch of graduate students coming in in the early 1960s, but a lot of money coming in: the Air Force grants were very generic unlike now, very broad, huge grants, basically to do research in seismology however one chose to define that

Interaction between Isacks and AFOSR [Air Force Office of Scientific Research] or AFCRL [Air Force Cambridge Research Laboratories]: when Isacks was graduate student, Jack Oliver handled that or to some extent the older graduate students; at that point a lot of the effort was on surface waves: this was the thing Lamont pioneered, Jack Oliver in particular, Jim Dorman, Jim Brune, they were all pioneers in surface wave analysis; Oliver's idea was you needed to diversify: he encouraged Isacks from the beginning to go into something else, the next big thing: Oliver got Isacks into something that was relevant to nuclear test detection business, but was not a the main stream of Lamont at that point: looking at the high-frequency end of the spectrum and Isacks got involved in a project in the New Jersey zinc mine (Ogdensburg) to set up high frequency seismographs, basically a kind of fishing expedition just to see what you would see: frequencies of 1Hz and higher, 1Hz being dominant teleseismic frequency; higher frequencies from local earthquakes (worked on earthquakes in the Caribbean, up to 20Hz); this work was somewhat off the main stream at Lamont, but of interest for problem of detecting P waves from bombs.

Any work Isacks did specifically on the detection problem? Isacks: not specifically in terms of detecting bombs; it was generally related to the problem of how high of a frequency can propagate to long distances in the earth (that would be of some significance for detection problem); the other problem was related to that: can you find sites which have very low seismic noise and how low is noise in holes 2,000 feet deep; one of the objects of his research was to look at seismic noise: how low a noise is it down there, how much better is it to put an instrument in a mine than put one on the surface; [during that time of course a lot of research about seismic noise was going on: AFTAC's [Air Force Technical Applications Center] work on deep holes etc.: any interaction between this work and Isacks work?] Isacks: no direct contact with AFTAC work on deep hole seismometry: most of the results of this AFTAC research was published in the gray literature, and Lamont had stacks of those reports, so they were aware of that; Isacks was looking at a somewhat higher frequency range, this set the two efforts apart a little bit AFTAC focused more on standard seismometers [l sec Benioffs]; other programs worked on these higher frequencies as well, so Lamont's effort in this area not totally unique (but he can't remember others who worked on it)

Ogdensburg mine: also construct a strain meter (baseline of order of 100m, quartz tube, capacitor pickup to measure displacement), done by Maurice Major (sp??) (he was a seismologist as well, grad student); Isacks doesn't know whether Benioff ever actually visited: Isacks doesn't remember; the Ogdensburg strain meter was certainly designed following Benioff s original concept; George Hade had a lot to do with the technical details of that instrument; the instrument was put in just in time for the 1960 Chile earthquake, remains the largest earthquake known: excited free oscillations of the earth, which were observed at Ogdensburg as well as other places around the world, and then let to a big breakthrough in the study of free oscillations (he was not really involved in that project); Ogdensburg mine was basically an observatory, instruments, file cabinets, almost an office plus a workshop down there: two main projects: one was the one Isacks was doing with the high frequency, and the other one was the one Maurice Major was doing on the strain meter: the two were completely independent projects; down in the mine there were also regular seismographs as well; it was also one of the WWSSN [Worldwide Standard Seismograph Network] stations for a while

Interaction with Jim Brune, Jim Donnan etc.: how would the interaction among the advanced graduate students look like? Were there regular seminars? Isacks: there was a weekly seminar, people would present research, and a lot of the course work was done in form of a seminar where they reviewed the literature; mostly the graduate students of the same year would get together, take a research seminar course and review the literature; Jim Brune was ahead of Isacks, so no courses together, but of course very aware of their work; Isacks would work as a younger graduate student with Brune: one summer working with him on model seismology, constructing two dimensional models of wave propagation (extension of Jack Oliver's work in early 1950s)

Role of early computers in Isacks's work: very little in Isacks's work as a grad student; Jim Donnan was the computer guru and Marc Landisman: worked with IBM 650 at Lamont; Donnan and Landisman did their surface wave dispersion calculations using that computer; Isacks didn't have too much to do with that; digital seismographs: we [Lamont in general?] did not do much with digital recording of seismology; most of the digital computing that they did during the 60s was theoretical computations to compare with the observations; Isacks got into PM tape recording in the mid-60s, but they never much with digital seismology, that came somewhat later: Isacks not quite sure when that started: probably the Lunar program had some of that; for a long time it was more efficient to record on magnetic tape using analog FM techniques

Digital signal processing: Isacks didn't do it in those days [early 1960s]: they would take the signal off of the tape and run it through analog machines, adjustable band path filters etc. (he did this a number of times) to do spectrum analysis all analog; they had an analog computer, made from operational amplifiers; big breakthrough came, Isacks thinks, when DEC came out with the VAX's (in the 1970s); in early 60s he doesn't remember any digital recording they were involved in, all analog.

Digital computers had a big impact: Jim Dorman's work, theoretical calculations, simply taking layered media and calculating dispersion curves for Rayleigh waves: impossible thing to do by hand, but with computer you can set up the matrices etc.; that's what was mostly done in seismology with computers; Marc Landisman was doing the same thing with Love waves, and Jim Brune got into this business; mid and late 1960s: people would take data from the WWSSN and digitize it; some of the big arrays may have recorded digitally [check when LASA changed from analog to digital recording]; mid 60s: not a lot of digital data available: you had to go and digitize it off the analog record; the big breakthrough in observations was the WWSSN with the long-period [LP] instruments; Vela's arrays were all short-period [SP] arrays (beam-forming); hand digitizing: how much of labor it would be to get the digital data; only digital network (1980s) provides substantial amounts of digital data.

Was the test ban issue discussed among the graduate students? Isacks implies that the general tendency was that the political situation provided money and the students didn't care too much about the political issues; Isacks: not that we were against it [test ban], but the interest of most people at Lamont was in fundamental seismology, making a big breakthrough in understanding the structure of the earth or interpreting some unusual wave form, and advancing the subject in its most dramatic and fundamental way; Isacks doesn't remember very much discussion or emphasis on political issues related to test ban; that was certainly in the back of people's minds, they were probably pleased to have a role in that, but Isacks don't thinks that that drove people; Isacks doesn't recall any faculty/student meeting where these political issues were discusses: more excited about surface waves and free oscillations; when the CTBT [Comprehensive Test Ban Treaty] was negotiated (70s and 80s) there was much more focus on people like Paul Richards at Lamont and Lynn Sykes: they were much more conscientiously saying, wow we are doing something for world peace; in early days it was much more "there is this huge amount of money coming into seismology, that we can have the opportunity to make really new observations about the earth and really discover new things"; Oliver of course was involved in the negotiations, so he was much closer, Isacks: in the hallway discussions, in the seminars, in the day to day scientific life, the political issues around the test ban were not prominent issue: Isacks cannot remember single instance of major discussion of how to detect bombs or what's the best method; Isacks says that the DOD program got more focused over the years (later yield estimates, how to detect hidden explosions etc.); but in early years [of Vela] primarily fundamental research

What changes in terms of research projects compared between late 1950s and early 1960s: [late 1950s emphasis on surface wave dispersion, because this is the line of Ewing and Press and Oliver; Isacks went to high frequency: were there other areas which were begun in early 1960s? Dorman with IBM 650; others?] Isacks not sure whether IBM 650 was financed through Vela, but as a young grad student he was blissfully unaware of how things got funded and who paid for what; other big impact that computers had on early days: Bruce Bolt was at Lamont for a while and he developed a program with Jim Dorman to locate earthquakes, one of the earliest location programs: to keep track of locations and seismicity was important part of bomb detection business; Isacks can't remember the name of the location algorithm by Bolt; Isacks: Sykes revised the program and used it for a lot of his early work: not a triangulation program: it is a least squares program: starts with a trial location [he describes in some detail how the method works], depth was also in there; this program helped later with deep earthquake zones; the program was breakthrough in defining spatial distribution of earthquakes around the world, and that was the basis for a lot of work they did with deep earthquakes; location accuracy: about 10km, good enough to see the boundary of the plates: for global tectonics 10lan works quite well.

Mid 1960s and his work on Fiji Tonga: Isacks was finishing his thesis and Jack Oliver looked again for a field that was completely untouched: they even had a seminar where the question was what were the interesting areas one should go into now; what's an area nobody has looked into and which was still very promising? (Sykes, Isacks, Latham and others looked at various subjects, and one of them was deep earthquakes and this fit the bill perfectly: they existed and nobody really knew why they were there; and that point Oliver apparently wrote an NSF proposal, and he let the grad students figure out the details; Isacks was the most interested in it, so he dug up the literature on deep earthquakes and looked around the world where they might do a project on deep earthquakes (around 1963; he went to Fiji in 1964); they found that Fiji-Tonga had most deep earthquakes in the world, so good chance of recording them down there, and compared to South America much more focused in location (in South America they would have to move between Bolivia, Argentina, Peru etc.: complicated); other reason was that one of the marine people at Lamont had spent a number of years on Fiji as the head of the Geological Survey there, and Jack Oliver knew him [Isacks didn't recall the name] because this man had operated one of the LP IGY instruments for Oliver; and this guy said that Fiji is a great place, very easy to operate there, very friendly, politically stable, British colony, so he encouraged Isacks; at that time the king of Fiji visited the US and the king stopped by at Lamont; he was friendly, didn't mind their earthquake investigation in Fiji.

Were any suggestions coming from Vela Uniform concerning deep earthquakes? Isacks: this was not designed for Vela: it was a conscious effort of Jack Oliver to do something in seismology different [from monitoring work]: Isacks pretty sure that there was no connection to Vela; Isacks says that they didn't think about depth discrimination: this was a NSF proposal; Isacks says that Oliver felt that Vela was going very strongly and he was trying to get something else going: not focused on surface waves, detection, etc.: conscious effort to go into another direction; Isacks: it was not about asserting independence for the seismologists from Vela, but taking advantage of other opportunities (NSF); Isacks thinks that it was an opportunistic thing to get another pipeline of support as well as another area of research; NSF grant of about $100,000 (big field operation, they had to ship stuff down there, Isacks lived down there for a year); Isacks: Oliver would seek out underdeveloped areas of fundamental scientific importance; then plate tectonics was not an issue, work on this subject was regarded at Lamont only as an interesting hypothesis, no big deal; F. Vine and D. Matthews gave a paper at Lamont about their Indian Ocean work: nobody at Lamont believed, thought data not good enough, too hypothetical; Chuck Drake said then, ''Too rich for my blood", not serious stuff; Isacks: people essentially ignoring continental drift.

Isacks: the change happened all within a year or less, because all of a sudden a whole bunch of things started to come together, interacted in a highly explosive way: marine geophysics, magnetism; Isacks: things started to come together was meeting at Goddard Space, that's when the marine geophysics was more or less began to click: Lynn Sykes realized that his work on the focal mechanisms, read Tuzo Wilson's transform fault paper, and Sykes felt that it made sense; Walter Pitman's stuff clicked, and Isacks and Oliver thought about the high frequency waves were, but Oliver didn't put it together with the seismic zones; Isacks: Fiji-Tonga had very little to do with Vela; Jim Brune tried to understand surface waves (more a Vela Uniform supported program), and using LP instruments you could get beautiful first motion records and construct the focal mechanism: it were the LP records that made that possible.

Plate Tectonics paper in 1968 ["Seismology and the New Global Tectonics"] and the role of data from the WWSSN for seismicity and focal mechanism patterns: Isacks: two aspects: the short period network: and the systematic reporting of P phases around the world essentially enabled the earthquake locating programs (PDE = Preliminary Determination of Epicenters), the ISS (International Seismological Summary): those programs were really enabled by that reporting service that the WWSSN provided; the other aspect was the LP records which enabled all kinds of seismological research; in terms of plate tectonics the real key input was in focal mechanisms: the P waves are very simple recorded on LP instruments: pulse like appearance that make it very easy to say whether it's a dilation or compression, whereas in SP this distinction is very difficult to make; the focal mechanisms one gets from WWSSN long-period P waves and S waves (which also have a much simpler form on LP instruments) this enabled seismologists to get really good focal mechanisms, very accurate: Lamont did this, St. Louis did this (Father Stauder was a pioneer in that); the patterns of these mechanisms turned out to be plate boundaries: key evidence in the plate tectonics story; direction of slip between the plates; key part of the paper Lynn Sykes wrote on the fracture zones, which turned out to be transform faults; the work we [Isacks and Oliver???] did on subduction zones; the other part of the paper was sort of summarizing the literature and pulling together a lots of different evidence from seismology that bore on the plate tectonic story; but the original work that we did: a lot of it was from the focal mechanisms and the locations of earthquakes and part of it was on the work from Fiji-Tonga where we showed that the deep earthquake zones were really contained within subducted lithosphere; subduction of lithosphere came out of Fiji Tonga work (paper he wrote with Oliver, 1967, showing that the high frequency phases in Fiji-Tonga could fit right into the plate tectonic model if you simply took the ocean plate, bend it down, and stuck it into the mantle and put the deep earthquakes into this piece of plate; the word subduction (Isacks and Oliver didn't use the term) came from a meeting after that result was known; the Japanese had observations which were in very good agreement and in retrospect he could probably have come to the same conclusion without ever having gone to Tonga, just taking the Japanese data; now evidence from two different places; but the actual connection lithosphere in the mantle with lithosphere on the surface, Isacks thinks that they were the first to make this connection.

Role of 1968 paper: comprehensive review paper, the original papers (Sykes, and Isacks and Oliver) came a little bit earlier; made it very accessible to both seismologists and geophysicists but also geologists and were struck by the weight of the evidence; very accessible way to get at the plate tectonics story and so it became widely cited; any seismologists after 1968 who remained skeptical of plate tectonics? Isacks: Maurice Ewing remained skeptical, not sure how much; Isacks doesn't remember any pervasive skepticism; Ewing was not so much skeptical of the seismological work but it took some convincing [from his work in oceanography he was not predisposed to believe in moving plates]; key factor with Ewing: in his oceanographic work he pioneered in the use of seismic reflection to look at the thickness of sediments on the ocean bottom, and saw that the ocean bottom was largely undisturbed, no evidence of deformation or disturbance of the sediments: he thought of the ocean bottom as a very quiescent, calm tectonic environment; continents "plowing" through the oceans didn't sound right to him: no evidence of such plowing, so he got this bias against continental drift; after a few years he was not actively opposing it, maybe he accepted it.

Interaction with other programs from the late 1950s to late 1960s: [Perry] Byerly, [Beno] Gutenberg, [Charles] Richter, [Stewart] Smith, [Hugo] Benioff, Ari Ben Menahem? Isacks: he himself didn't have a lot of close interaction with these people, Jack Oliver knew a lot of those people much better; Isacks never met Gutenberg, saw those people at meetings; Isacks: Lamont was a fairly large place so one could do a lot of work and have lots of colleagues; so he didn't have much close collaboration with people outside of Lamont at that point.

Isacks worked with Lynn Sykes not until the Fiji-Tonga project; worked with Oliver of course; work with the Ogdensburg mine, he did this pretty much on his own with Oliver in the background; in the late 1960s a number of new students were coming through: as post-doc Isacks was something like an advisor to some of those students: Barazangi, Molnar; they were getting involved in plate tectonics work; a lot of the [page missing] integrating in one fairly comprehensive package to make it rather overwhelming; Isacks uses it in his courses, very accessible, easy to absorb and to be very convinced by the evidence; Isacks: if we had not written that paper maybe someone else would have written the pieces that were original in it in separate papers; Isacks: it had a kind of stimulating effect; Isacks: certainly seismology played a key role; concerning plate tectonics in general: Isacks: what turned most people around including the people in seismology was the geomagnetic profile, and the symmetry of the profile: Isacks: that was probably the most convincing: symmetric anomaly pattern; it has in it the magnetic field reversals; chronology of the earth field reversal established on volcanoes, on land, and then having that chronology laid out on the ocean floor, picked up so perfectly by magnetometers on the surface of the ocean, that was probably the most important result: established sea-floor spreading; second to that are the transform fault ideas; and of course the whole plate idea

Classes he took at Columbia and teachers who were influential: Isacks: the philosophy of Lamont at that time was pretty much determined by Ewing: his point was that grad students came to Lamont to do research, if you wanted to take courses, fine, go down to the physics department, or the geology department; so Ewing and Oliver didn't teach any courses, Jack Nafe taught a course in oceanography, Joe Worzel taught an exploration geophysics course: Isacks took this course (only geophysics course he remembers taking) and a lot of physics, a lot of geology; no one course that particularly got him into seismology; he appreciated the undergraduate physics labs; and he did a lot of geology field trips.