On Shaky Ground

by Nance, John J. ;

  Established science would have nothing to do with Wegener’s fanciful ideas about drifting continents (despite two additional books on the subject by other scientists published a decade later), and for the next three decades the matter received little serious attention. Worse, any scientist who attempted to explore the theory ran the risk of professional ostracism.

  But there were problems with the dried apple theory as well, and they kept cropping up every now and then to bother earth scientists who were beginning to discover new facts about earthquakes that wouldn’t fit the classic model of the earth’s crust.

  A Japanese seismologist by the name of Kiyoo Wadati was one of the first to realize that his data formed a square peg in the round hole of the accepted view of the planet’s surface features. By the late 1920’s he had spent enough time poring over seismograms of Japanese earthquakes to discover a curious trend: There was a dipping plane of earthquake epicenters diving from a shallow depth under the east coast of Japan to a great depth under the Asian continent. They seemed to start at the Japanese Trench, a great underwater valley or canyon off the Japanese coast, but they became progressively deeper as they moved to the west. Wadati recomputed and refigured and rechecked his data endlessly to be certain, but the conclusion remained the same: The epicenters recorded on Japanese seismographs reached startling depths of four hundred miles down beneath Manchuria.

  The dried apple theory held that below fifty or sixty miles the earth’s interior was hot liquid rock, and molten rock can’t shear in such a way as to cause earthquakes. What, then, was happening? Wadati kept probing, but reached no overt conclusions before the investigation was taken up by a man who had helped refine the design of the modern seismograph, Caltech’s Dr. Hugo Benioff. Benioff began documenting the same phenomenon in other ocean trenches around the Pacific, finding the same dipping trend, which he reported in his breakthrough paper of 1954.

  But the same rejection of the idea of a mobile planetary crust that led the scientific community to such abuse of poor Alfred Wegener began eroding Benioff’s findings almost immediately, although in a more metered way. Benioff had obviously done his “homework,” supporting his findings with excellent and voluminous research which showed that the entire Pacific basin was ringed with such zones of dipping earthquake hypocenters always radiating out and down beneath an adjacent continental landmass. At the end of the paper Benioff concluded that these were actually mammoth sections of the ocean floor—slabs—which were plunging downward into the earth’s interior, and since they did not melt until at great depths, their continuous downward movement created the constant earthquakes which he had mapped.

  Collectively, the seismological and geological community acknowledged that something was happening, but it was too soon, they said, to conclude that whatever it was had anything at all to do with moving slabs of ocean floor, plunging or otherwise. After all, if gigantic slices of the earth’s crust were plunging back into the planet’s interior, what was replacing them? The dipping planes of earthquake hypocenters dubbed Benioff zones might be evidence of some other process, said the established seismologist. Perhaps, some suggested, the plates were emerging from the earth’s interior at those ocean trenches rather than submerging. Benioff “obviously” had jumped too rapidly to a conclusion.

  Dr. Hugo Benioff was a quiet and studious scholar of great capability who held the respect of the scientific community (no less a giant of seismology as Dr. Charles F. Richter of Caltech was a Benioff protégé). He took the criticism in stride, but increasingly it sent him back to reexamine his research, concerned that perhaps he had overlooked something or indeed had published too soon.

  He hadn’t. More geological and seismological discoveries were starting to come in with relative rapidity by the late fifties, the more startling among them the results of several initial years of marine geological research in the Atlantic ocean.

  No one had really known what lay on the bottom of the Atlantic Ocean. Certainly it was assumed that miles of sediment overlay bedrock, but no one had mapped the ocean floor and its substructure. In the mid-fifties, however, Columbia University’s newly established Lamont Geological Observatory (later renamed Lamont-Doherty) began to do just that, using a specially outfitted three-masted schooner, the Vema, in a multiyear effort to find out what the bottom of the Atlantic looked like, and what it was made of. The scientists began using seismic refractive devices, which “listened” to the echoes from underwater explosions bouncing off the rock strata below the ocean floor, giving clues to what types of rock structures were down there. It was a crude beginning filled with shadowy returns that required much interpretation. To almost the same extent as seismology’s efforts to deduce the structure of the center of the earth by reading the seismic waves that passed through and around it, the Vema’s task was as complex as an attempt to reproduce the entire structural blueprint of a fifty-story building by tapping the outer wall and interpreting the echoes returning from within.

  Nevertheless, from the very first the results were startling.

  To begin with, the depth of the sediments was not the same in different parts of the Atlantic. They were thickest along the shores of North America and Europe, but progressively thinner toward the middle of the ocean. That made no sense—or did it?

  Then the picture of a zone of mid-ocean underwater mountains began to emerge as a unified system of incredible proportions. The Atlantic Ocean was bisected from north to south for thousands of miles by the strangest mountain range on earth. Instead of sharp peaks in the middle, there was a valley running the entire length of the north-south underwater mountain system, sometimes many miles wide. What’s more, at certain points the range simply came to an end, its southward march beginning again miles to the east or west, as if it had been torn apart by a right-angle fault. Additional data showed the temperature of the ocean floor near the mid-Atlantic rise (as the mountain range was quickly named) was hotter than the crust near the edge of the continents, and by 1960 data had begun to show that the age of the rocks at any point on the eastern side of the mid-Atlantic rise was the same as the rocks an identical distance to the west of the rise.7

  Marine geologists, as they were being called, were becoming active all over the world as the new World-Wide Standard Seismograph Network came on-line in the early sixties, and the data they were gathering showed similar mid-ocean ridges in parts of the Pacific (the East Pacific rise off Central and South America) and other oceanic areas. In addition, when small underwater earthquakes occurred, they seemed to center exclusively in mid-ocean ridge areas.

  It was becoming increasingly difficult to avoid putting the evidence all in a row and coming to the preliminary conclusion that new crust was being generated in the mid-ocean rises, and was moving away in both directions, accumulating more sediment with time like some sort of planetary conveyor belt system.

  But where did it go?

  At the same time that the evidence was mounting for a moving ocean floor, several prominent marine geologists, such as Lamont’s Dr. Maurice Ewing, were concluding that mid-ocean trenches (of which there were none in the Atlantic but many in the Pacific) were actually zones of extension, or at least stable areas.8 That not only failed to dovetail with the tentative theories arising from research in the Atlantic, it contradicted Dr. Benioff head-on.

  Despite an eloquent presentation in 1963 by Dr. Harry Hess of Princeton, which provided one of the earliest models of what was probably happening (crust coming up in the middle of the rises, moving the continents along like a conveyor belt, and the ocean floor on the other side being consumed beneath the advancing continent), the emerging picture was still considered radical. In fact, Professor Hess himself, tongue firmly planted in doctoral cheek, described his theoretical model as “geopoetry” in a rather brilliant turn of phrase which at once defused the expected criticism of nervous colleagues while it raised the structure of the emerging idea into the light of further worldwide examination. No one yet dared breathe the
name of Alfred Wegener, but all those in earth sciences who were following the exciting march of discovery were holding their collective breath, waiting for a breakthrough, or a definitive statement.

  And, in March 1964 Dr. Hugo Benioff, having been professionally pushed and shoved, niggled and attacked (however gently) for his supposedly premature conclusions, disregarded the broader implications of the newest research and succumbed to the pressure. Benioff issued a new paper in which he reinterpreted his own data—the data he had so brilliantly presented in 1954—concluding that the first time around he had been wrong to deduce that his Benioff zones had anything to do with dip-slip faults, or plates thrusting one beneath another. Using the purely mathematical approach as his basic guide, and disregarding even Professor Wadati’s findings published before him, Benioff fell into line with Dr. Frank Press and others in concluding that the engine of the great quake in Chile and similar quakes in Benioff zones was actually counterclockwise horizontal movement of the Pacific Ocean floor, or steep faults deliniated by the Benioff zones.9

  “Poor old Benioff,” George Plafker recalled as he sat on the shoreline of southern Chile in January 1968 and prepared to return to the boat. What Plafker had seen in Alaska and Chile left no doubt that Dr. Benioff’s original conclusions had been prophetic and dead right, yet the eminent senior seismologist had lost the confidence of his original conviction and thrown in the towel with that paper.

  But the irony—the extreme irony—was in the timing. Benioff’s retreat was published on March 27, 1964—the very day of the Good Friday quake, the examination of which would eventually prove him right.

  Chapter 12

  Menlo Park, California—Fall 1970

  Fuzzy facts.

  It was a phrase he loved to use—a phrase scientists weren’t expected to use.

  “We geologists tend to gather fuzzy facts, and after evaluating them, we seem to want to go out and gather even more fuzzy facts.”

  Dr. Robert Wallace’s wry, almost impish sense of humor was evident around the corners of his phraseology as he described the differences separating seismologists, geophysicists, geologists, and engineers. Emphasizing such contrasts, however, was part of the melding process—part of his constant, gentle preaching on the subject of how the various scientific disciplines needed one another to solve common scientific problems facing them all.

  “Geophysicists think differently than geologists. It’s the mental process. Like seismologists (who consider themselves geophysicists), they tend to be more mathematically oriented, and so they tend to take a problem and simplify it so they can describe it mathematically. That produces some very important constraints. The problem, in other words, can’t lie outside this boundary over here or that boundary over there. That’s marvelous.”

  Wallace seemed perpetually amused at the differing methods of problem solving used by colleagues in diverse areas of the scientific community.

  “Geologists end up coming to a synthesis of multiple suggestion. I’m perfectly comfortable as a geologist with a lot of loose ends, a lot of things that don’t fit, lots of things that are not hard facts, [that are] fuzzy observations. Geophysicists and seismologists [on the other hand] want to go out and get a hard fact, a number, and if it shows on an instrument, then it’s real to the geophysicist, and you can analyze [it], and that’s good. Good science!

  “The point is, they’re both reproducible, and that’s the essence of science, the fuzzy facts and the hard facts.”

  Bob Wallace sat back in his chair in his neatly packed and organized office in the U.S. Geological Survey’s western headquarters in Menlo Park and looked at the autumn leaves blowing around the adjacent tree-shaded parking lot in the gentle embrace of a late-afternoon zephyr. He was alone now at the end of the day, and cascading through his mind were thoughts and ideas, projects and observations, a germinating overflow spilling from a cornucopia of excitement in the scientific community—an excitement which always seemed to exhilarate him.

  It had been six years since a phone call from his wife had found him similarly deep in thought at the office on the night of March 27, 1964. She had heard the news of the great quake in Alaska, and though the Menlo Park complex all around him was the epicenter of West Coast seismic research projects, the after-hours quiet of his office (a block from the nearest seismograph) had isolated him from the news. Thinking of that quake now was quite significant because it had altered so much so very rapidly. The changes in professional life within the U.S. Geological Survey from 1964 to 1970 were, well, seismic. Suddenly earthquakes were important items.

  But Wallace was a senior geologist, not a seismologist, which made his present, increasing interest in things seismological all the more intriguing. Yet that had been one of the most important changes, the technical transfer of information, research, and expertise among the various scientific disciplines.

  For one thing, people were talking to each other across professional lines, at long last. Wallace had become a passionate advocate of the concept that there was great synergistic value in the cross-pollination of ideas and observations between seismology and geology, though that had traditionally seldom occurred in any structured way. It was obvious to him, however, that both fields needed each other to understand the problems they faced.

  And now, thank heaven, that kind of communication was occurring with increasing regularity.

  Before the 1964 cataclysm in Alaska, geologists and seismologists exchanged pleasantries in the hallways of Menlo Park and occasionally at parties, and that was about it. The two disciplines were miles apart. Suddenly, however, geologists such as George Plafker had come along to hand the seismological world some seminal observations from geology. Plafker, in addition to his other research, had found benches (flat areas above a beach eroded in past centuries when the bench was, at that time, the beach itself) in Alaska, clear evidence that previous great quakes had dropped and raised beachfront property many times before 1964. That was a geological revelation contributing directly to the quest for an answer to a seismological question.

  George Plafker had impacted geophysics as well. His paper on the Alaskan quake of 1964 had provided one of the last important keys to the emerging theory of plate tectonics. In fact, it was during a landmark meeting of the American Geophysical Union that Plafker’s paper, along with some seventy others, was read, helping push the theory over the top with his clear evidence that oceanic plates were being shoved under the continental plates. The result was the final, utter destruction of the last, battered elements of opposition to the general concept that Alfred Wegener had postulated fifty-three years before. It became obvious from that meeting that the earth’s crust indeed is composed of segmented plates of mammoth proportions that are in dynamic and continuous motion.

  Overnight the entire geophysical world changed. Suddenly in that model of moving continental plates were answers for which no one had yet formulated questions.

  And—a rarity in the lives of earth scientists—suddenly there was research money available. Not an unending cascade of cash, but a newly uncorked pipeline of funding for studies and projects which were beginning to change the face of science on what seemed like an ever-accelerating basis.

  The great Alaska quake of 1964 was responsible. It had shaken up not only the forty-ninth state, but the governmental establishment as well. The fact that an American community could be hit so hard (and that its misfortune could cost its fellow taxpayers so dearly), instantly focused many political minds on the reality that such disasters could occur as well in the continental United States. From the White House to Capitol Hill there was sudden recognition that the country’s knowledge of the true level of risk from major earthquakes, and of what could be done about that risk, contained questions that must be answered, and soon. Thus the national spotlight began to shine on the campuslike atmosphere of Menlo Park (and the USGS headquarters at Reston, Virginia).

  As Wallace and his colleagues watched with growing optimism, research pr
ojects that had been fiscally impossible to finance just a year before were being discussed with real hope of future funding.

  One of them was his, a stillborn project in 1963, when he and Dr. Parke Snaveley had tried to sell it. The two of them had lobbied long and hard to convince the USGS to fund the two million dollars necessary for an ambitious program of research into the mechanisms of the San Andreas Fault. The famous rift, which cut through California from south to north and was the culprit in a great quake at Fort Tejon (north of Los Angeles) in 1857, as well as the great quake that devastated San Francisco in 1906, was still largely a mystery. It was an incredible fact, but very little really was known about the potential for more great quakes on the San Andreas. It was assumed that ruinous quakes were both possible and probable, but Wallace knew that the body of geologic knowledge about just what made the San Andreas Fault move (and what happened seismically when it did) was in its infancy.

  Before the plates had snapped beneath Prince William Sound, there were no funds to go any further into the question. The USGS wouldn’t buy the idea—which was to say that it did not consider the study of long-range earthquake potential sufficiently urgent and promising to warrant taking someone else’s funding—as would have been the result.

  By 1965, however, neither the public nor the USGS leadership could get enough information on the subject of damaging earthquake potential in California. Suddenly Bob Wallace’s project on the San Andreas was viable, and with funding and approval in hand, he had happily dusted off his field equipment and, in a professional sense, gone home.

  Wallace’s roots as a geologist were in the San Andreas. As a young graduate student at Caltech in 1938 he had been required to do two complete theses. His first concerned vertebrate paleontology, but the second—which would grow to be a passion—was focused on the nature of the San Andreas Fault, the worrisome geographic and geologic oddity which split California nearly end to end.