On Shaky Ground

by Nance, John J. ;

  By 8:00 A.M. the shocked residents of Los Angeles began picking themselves up and taking stock of the damage, bracing for aftershocks, and wondering what would happen next. Was the quake a precursor? Would something worse follow?

  As excited seismologists poured over the wild tracings of the seismograph record at Caltech (and the USGS monitoring center in Golden, Colorado, calculated a Richter magnitude ML 6.1), an aftershock of ML 4.4 rumbled through the area, its epicenter only slightly removed from the main break.

  Los Angeles was indeed stunned. Nothing had rocked the area with that much force since the 1971 Sylmar quake in San Fernando. Cracks had appeared in L.A.’s City Hall, offices and homes were littered with items thrown from shelves, and windows in various places were in pieces. The glass windows of the control tower at Hollywood-Burbank Airport had exploded outward, closing the airport for twenty minutes as controllers tried to slow their heartbeats and regain control of the traffic situation. And, of course, Whittier lay bruised and bleeding.

  “This,” said one breathless television newsman at NBC’s studios in Burbank, whose image had been substituted suddenly for the western time zone transmission of the Today show, “may be the big one.”

  But it was not the “big one.” In fact, said one seismologist at Caltech within hours, it was merely a seismic “fender bender compared with what’s still out there to the north in the San Andreas.” The quake had been a rather insignificant readjustment in one of the smaller faults beneath eastern L.A., but with no ground breakage apparent at first, seismologists couldn’t quite figure out why the epicenter of the quake was located more than five miles from the spot where most of the damage had occurred. Perhaps, said one, we have a dipping fault plane here rising toward Whittier.

  By 9:00 A.M. it was obvious that L.A. was neither burning nor heavily damaged. With the exception of widespread shock and seven deaths (and about a hundred injuries), and, of course, the destruction centered around Whittier, there was a cautious feeling of euphoria in the city. At ML 6.1 it was less than a third the magnitude of the 1971 quake. Nevertheless, it was also apparent that steps taken since 1971 to reduce hazards had worked: No freeways collapsed, even those adjacent to Whittier, due in part to retrofitting of all bridges and overpasses with metal strap restraints to prevent the type of disconnection collapse that had occurred in 1971. The Southern California Earthquake Preparedness Project’s influence could already be seen in both the efficiency of the emergency response from all over L.A., and the performance of buildings throughout the area. Newer buildings and many refurbished buildings throughout the city performed well, while many newer buildings in Whittier, even in the absence of a stringent seismic code, responded adequately with minimal damage. Water systems, electrical systems, and sewers for the most part came through intact (with some exceptions), and communications—especially for emergency response services—came through beautifully. Even the satellite dish antennas connecting the big three networks, the Cable News Network, and others with the rest of the world joined the majority of the phone system in continuing to work.

  Angelenos had indeed survived an earthquake—but not much of an earthquake. Whatever euphoria existed flew in the face of the reality of what was coming, as the media quite properly began reminding their audiences. However well their metropolis had performed this time, they had yet to be tested by the earthquake which was still in the future.

  There was a good news/bad news air to the analyses which began by late morning. L.A. had survived far better than expected and reacted in terms of emergency services far better than in 1971 because strict seismic codes had been enacted years earlier, freeways had been strengthened, a generation of children as well as adults had been exposed to earthquake preparedness information, and more than a third of the hard-core dangerous unreinforced masonry buildings scheduled to be destroyed or rebuilt by 1990 had been finished off, one way or the other.

  But the bad news included some sobering realities, such as the fact that seven thousand targeted buildings still remained occupied and unreinforced, and outside Los Angeles proper, wholly inadequate or nonexistent seismic building standards permitted many tens of thousands of other marginal buildings to stand unchallenged. Then too, there was the reality that L.A. had not really been tested. A ML 6.1 event was a puny nudge compared to the nearly one thousand times increase in the energy and more than a hundred times increase in the magnitude of the great quake which Dr. Kerry Sieh’s research had proven occurs along the southern San Andreas on the average of every 140 years.

  “Nature,” said a Los Angeles city councilman, “has merely issued us a warning.”

  By Friday damage estimates had risen to sixty million dollars as the aftershocks continued, all of them minor, but very upsetting. By Saturday morning, one seismologist at Caltech was warning that the aftershock sequence wasn’t right. Kate Hutton told reporters that the aftershocks were migrating deeper into the ground beneath L.A. and migrating in a northeasterly direction. While it appeared, she said, that there was “less than a one percent chance of a bigger quake coming out of Thursday’s earthquake,” the absence of a hard aftershock was puzzling.

  To the residents of Whittier, it was also nerve-racking. Many of the damaged buildings and houses had cracks snaking through masonry in chimneys and walls and foundations that could ill afford another hard shock. The partially collapsed parking structure on the south end of town would go down completely with another jolt, as would, it seemed, the rest of the St. Mary’s school building. With hundreds sleeping on their front lawns, in the parks, or in community shelters—children and adults alike traumatized by the disruption and uncertainty—Whittier picked at its wounds and waited.

  And then came the twenty-second aftershock, a jolt that struck out once again from beneath an area six miles northwest of Whittier at 3:59 A.M. on Sunday morning, ripping up at an angle toward much of the same area, jolting the ground beneath Whittier and Alhambra alike, and delivering a coup de grace to scores of damaged buildings. As jittery residents awoke in now-familiar fear, the sudden jolt completed the job begun Thursday on the Whittier parking garage, sent a bell tower crashing through the roof of the San Gabriel Civic Auditorium, shattered many of the remaining masonry joints in St. Mary’s School, tumbled chimneys and walls throughout the area, and launched the newly repositioned contents of a thousand bureaus and tables, shelves and bookcases toward the floor once again with a seismic magnitude measured at ML 5.5. There apparently had been a deficit in the aftershock sequence, but it was now resolved.

  “It was the oddest thing,” the man said, standing in the shattered front room of his rented house in Whittier, a house damaged now beyond hope in the aftermath of Sunday’s aftershock. “I was forty miles away when it hit Thursday. I had no idea what had really happened.”

  Ron Reader shook his head as he watched his neighbors across the way, stumbling in shock around a little house they had spent three long, hard years remodeling and polishing. They had finished just two weeks before. Now it stood in ruins, the foundation shattered, the chimney gone, an ominous red warning sign posted on the front door by the building inspectors, who had declared it too dangerous to occupy. Next door a rental moving van sat at the curb, watched by an elderly lady in an easy chair, sitting incongruously in the street and watching the efforts of her son and daughter to pack her things. Her shattered home of thirty years lay broken and slumped, her pictures of a lifetime strewn about the cluttered living room, her furniture bearing the scars of fallen plaster. The lady watched without tears. “I have earthquake insurance,” she had said. “I just don’t know what I’m going to do in the meantime.” On her front porch, too, was the telltale red warning sign, as with the next house down, where a tearful couple poked in desultory fashion at a growing pile of their furniture arranged on the front lawn.

  Reader shook his head again. “I didn’t know [at first]—they said ‘Pasadena’ on the radio—so I’m just coming home, and I thought we would have some damage h
ere; but I didn’t expect anything like this. But what kind of brought me up to the point where I knew it was [going to be] worse was the physical posture of people in the street.

  “About four miles away in Norwalk—I grew up there—there was some stucco down, but there were people standing in the street and just talking. As I came this way, there were people just standing in the street, talking and waving their arms and pointing, y’know, look at this! I got closer, and there were people standing and staring into nowhere, then people sitting on the curbs with their heads in their hands. Then I got within a few blocks and I saw people standing and crying openly, pitifully, and I thought to myself, Oh, Lord, this is serious! Then I get here, and, well, it’s a total loss.”

  The man paused again, looking once more around the shattered neighborhood and shaking his head in solemn disbelief.

  “If this was just a little one, I can’t imagine what the big one will be like.”

  Chapter 26

  University of Washington, Seattle—April 1988

  It was hard to believe such tranquillity could be shattered suddenly. The stately campus of brick and masonry buildings set amidst tall trees encouraged the uniquely human delusion of permanence, as if the endurance of the works of man is superior to the destructive potential of nature.

  Dr. Brian Atwater paused for a moment, looking to the south through the windows of his third-story office in Johnson Hall at the campus and the city beyond, acutely aware of how unprepared it all was for the type of cataclysm which had struck this ancient meadow many times before these buildings had risen—a type of great earthquake which could (and would) strike again someday.

  He had found the smoking gun: evidence in the muds of streams and estuaries along the Washington coast—evidence of sudden drops of the landscape which had probably occurred during periodic great subduction zone earthquakes in past centuries—evidence that the Pacific Northwest was indeed at extreme risk.

  Yet his descriptions had to be carefully worded, professionally at arm’s length with the increasingly compelling nature of the evidence, and his words properly restrained. “The great-earthquake hypothesis,” Brian had said, “… is hanging together very well.”

  The remnants of suddenly inundated marshes he had found, and the dark, decayed material (peat) he had so carefully carbon-dated during the past summer told a frightening tale of massive tectonic upheavals off the Pacific Northwest coast, the last one occurring only three hundred years before. Yet this city, this state, and indeed the entire region were unprepared. The building codes were based on a seismic zone 3; but zone 4 was both the highest level of risk classification, and the one more appropriate for the Pacific Northwest if he and a growing cadre of other scientists were right, and the Pacific Northwest faced an earthquake far greater than anything California’s San Andreas Fault could ever deliver.

  And he was becoming convinced that the only real question was when, not if.

  “What impressed me the most,” Brian had said, “… even more than the radiocarbon evidence of the various events, was seeing similar sequences of suddenly immersed marshes at a wide variety of places.”

  Those black layers were not elements of conjecture, or convoluted technical descriptions in the form of cold words in a professional paper. They were black layers of decayed material in three dimensions exposed by the shovel blade at various places, interlaced with ancient seeds and the roots of certain marsh grasses, exhumed and explained by Atwater. They were remains of grasses and plants which had died when their meadow or marsh had suddenly dropped in elevation four to six feet perhaps on some ancient evening, plunging them below sea level (in the intertidal zone). And some were layers coated with a sand which could have only been transported there on the back of a raging tsunami.

  As the summer of 1987 passed and fall brought Dr. Atwater and the samples back to his tiny USGS “encampment” at the University of Washington, the results were compelling.

  “What I was testing,” he explained, “was whether the jerks [of marsh submergence] had sufficient regional extent to represent magnitude 8 earthquakes. In other words, did the ages of the buried marshes at one place reasonably match those at other places in a coastal strip eighty-five kilometers long and thirty kilometers wide. In the summer of 1987 I learned that at least two of them do. A large stretch of the southwestern Washington coastal area sank suddenly seventeen hundred years ago, and again just three hundred years ago.”

  There had been similar findings by other geologists in Oregon in the meantime—findings which indicated that the jerks may have resulted from earthquakes of magnitude 8.5 or even larger.

  In addition, there had been another large event sixteen hundred years back (perhaps a hundred years after the one that carbon dated at seventeen hundred years), evidence of which Atwater found in the strata of Willapa Bay and Grays Harbor, Washington.

  And there was a jerk a thousand years ago which produced the dark line in the stream bank near Neah Bay that had been Atwater’s first clue.

  There had been widespread jerks twenty-seven hundred years ago and thirty-one hundred years ago at Willapa Bay and Grays Harbor, and also thirty-four hundred years ago (dated thus far only at Willapa Bay).

  “It’s a repeat time average of about six hundred years, and the last time southwestern Washington was hit was three hundred years ago. But does that mean we’re safe for another three hundred years? Not necessarily.

  “Though the average is about six hundred, the radiocarbon ages indicate that the jerks can occur as little as one hundred years apart, or as much as a thousand years apart. There doesn’t seem to be a lot of regularity in the repeat cycles.

  “In other words, the next jerk conceivably could happen tomorrow, or it could be in seven hundred years in the future.”

  Brian knew that the seismological community had yet to come to grips with the growing evidence. He had not yet presented his research formally, so the rest of the geophysical community had yet to review it, let alone draw conclusions of repeat cycles.

  But that review was about to begin. As Brian Atwater stood at the window, the abstracts of twenty-two professional papers that had been presented at a December 1987 meeting of the American Geophysical Union in San Francisco sat on the desk before him. His preliminary findings were there, too, along with abstracts from supportive papers of research just completed in Oregon, which had found evidence of the same types of sudden dropping of coastal areas, and of similar dates for the events.

  And there were papers by seismologists who sought to argue with the original, theoretical conclusions of Dr. Tom Heaton of USGS at Caltech that the Cascadia subduction zone parallel to the Washington-Oregon coast was a seismic time bomb.

  Heaton, in many respects, had started the whole thing. It had been his presentation which had drawn Brian Atwater and others into this increasingly exciting investigation. It had been Heaton (and colleagues) who had argued several years before that the subduction zone off the Pacific Northwest coast was too similar to the great earthquake-producing coastal areas of southern Chile and southern Japan to be quiet (aseismic). Many other seismologists had taken on Heaton with theory-to-theory arm wrestling over interpretations of seismographic tracings, trying to deduce what was really down there and whether the Cascadia subduction zone could indeed produce great quakes.

  But those arguments had been based on broad theories, not physical evidence. And the December conference had included more theoretical arguments that the Pacific Northwest was not subject to great earthquakes from the subducting of the Juan de Fuca tectonic plate beneath the North American plate.

  “What else could [cause those layers]?” Tom Heaton had asked Brian on the phone. While the conclusion that great earthquakes were responsible had not been formally established, it was difficult to see how anyone could come up with any other credible explanation.

  The subject had hung in the very air of the San Francisco conference, yet the process would have to proceed as a steady trek through
the jungle of scientific caution and professional skepticism designed to weed out insubstantial theories and conclusions. Brian would have to defend his position, describing his evidence and his methods in scientific journals (as would the other geologists who had found similar evidence in Oregon). Provided no great quakes erupted in the Cascadia subduction zone in the meantime to make the debate academic, and provided Brian’s paleoseismic inferences would withstand the scrutiny of his peers, it might still take years before the paleoseismological, geological, and seismological communities would be sufficiently convinced to stand as a group, square their collective shoulders, look the people and the political leaders of the Pacific Northwest in the eye, and deliver the frightening news: “The possibility of a future great earthquake as large as Mw 9.2 has been confirmed. We just don’t know when to expect it.”

  Yet the process of getting a population and its buildings ready for such a quake would take decades, and every second would count. Within a week he would be presenting the evidence once again, this time to a major earthquake preparedness workshop organized by the USGS in Olympia, Washington. It would be a meeting of scientists, emergency preparedness experts, engineers, politicians, and insurance company representatives, all of whom would be starting the arduous process of coming to grips with a growing reality: that the Pacific Northwest is subject to a far greater seismic danger than ever before believed.

  Two floors beneath Brian Atwater’s office, the state of Washington’s unofficial “state seismologist,” Linda Noson, sat at her desk and considered the questions.

  If the people of the Pacific Northwest were convinced a great earthquake could strike their homes and businesses, would they get busy and start reducing their exposure? Would they support programs to make school buildings safer, educate the population on what to do if the ground started shaking, and support more stringent seismic codes?