On Shaky Ground

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by Nance, John J. ;


  “I’ll tell you what the lesson of this disaster was. The lesson is that the only way a devastated community can get itself back together, the only way people will be able to carry on and put their lives in order with any degree of assurance, is if they know their losses are going to be covered. I don’t mean every cent. I don’t mean everything’s going to be exactly as it was. But to know for sure as you wobble out of the wreckage that, hey, we’re going to rebuild—to be able to tell your kids that with firmness and know you’re not lying—that’s what we need. How do you do that? Insurance. Good, low-deductible policies which cover earthquakes in full. We have to have fire insurance for a mortgage, why can’t they require earthquake insurance? In my opinion, we need that right now, nationwide, for all natural hazards. A way to equitably—evenly—distribute recovery funds without using tax money.”

  “And I’ll tell you,” he continued, “a national insurance program giving better rates to those who built buildings and houses to withstand quakes would be a double-barrel benefit.”

  Indeed, it isn’t the noble efforts of recovery and emergency aid that hold the greatest societal promise of taming the specter of earthquake disasters; it’s the incentives that can be created to prepare our buildings and our cities, coupled with a national sharing of the risk through insurance which becomes the ultimate safety net beneath the high-wire act of life on an earthquake-prone continent.

  Chapter 21

  Michoacán, Mexico—September 21, 1985

  The road ahead seemed to disappear into nothingness, the sudden curve to the left around the flanks of the mountain invisible in the pitch-darkness of the moonless night, the twin beams of the Travelall’s headlights soaring off into infinity over an unseen abyss. David Smollar, a reporter for the Los Angeles Times, gripped the armrest even harder as he watched the driver for some comforting indication that she was going to follow the road, and not the headlights. Dr. Karen McNally had been gesturing energetically for the past half hour, her hands describing compression waves and surface waves, subduction zones and seismic gaps in the dark, humid airspace above the dashboard as they roared through the hot Mexican night, bound toward the Pacific coast north of Acapulco—a retinue of other rented vehicles behind them carrying a joint Mexican and American team of seismologists.

  “You really shouldn’t be asking me these things while I’m driving, David,” she had volunteered thirty minutes and several hair-raising curves back.

  “I know,” he had responded—followed by another round of questions.

  As Karen smoothly negotiated the curve on the rough, remote highway, the surrealistic aspect of their mission was not far from her thoughts. It was now late Saturday night, but it had been two days before—Thursday morning September 19th, around 6:30 A.M. on the U.S. Pacific coast—when the USGS earthquake-monitoring center in Golden, Colorado, had dialed her number in Santa Cruz, California. Minutes before the call, the seismic gap she and so many other scientists had studied and warned about in the Mexican state of Michoacán had rumbled to life in a great quake exceeding a surface wave magnitude of Ms 8.1, flattening several coastal towns and radiating monstrous seismic wave trains throughout Mexico. The seismologists at Golden were waiting for word from Mexico, but in the meantime, they needed help. Would she go back to the university lab to read her seismograms and help locate the epicenter exactly?

  Mexico City couldn’t respond. Not yet, at least. Its central communications microwave link was in shambles, as transmitters and antennas had slammed back and forth inside their concrete communications tower until they had been reduced to useless junk, the long-distance systems and satellite relay systems going down at the same time. Without it, the rest of the world had no idea of what had happened—what was happening—in the world’s most populous city of eighteen million people.

  It had started 47.6 seconds after 7:17 in the morning, when the snag holding back the accumulated tectonic energy in the subduction zone northwest of Acapulco had shattered without warning, the Cocos Plate and North American Plate rumbling past each other at the northwestern end of the Michoacán gap, creating huge seismic waves, which traveled outward at 4.3 miles per second, shuddering the foundations of Mexico City 230 miles away 53 seconds later just as the capital city was awakening to another business day. The initial shudders of the P waves, and the beginning undulations of the S waves did little to upset the populace in the first few seconds—the memory of another minor tremor several days before was very fresh. It had passed harmlessly. So would this.

  As the initial seconds ticked by and the surface waves began to move the foundation of Mexico City back and forth laterally, the amount of energy contained in one particular frequency of waves began to build up to unprecedented proportions, relaying incredible pulses of energy to the rock beneath most of the Mexican capital, and to the deep lens of alluvial, unconsolidated muds and clays and sediments which had filled the northwestern corner of an old, drained lake known as Texcoco.1

  The ground began to move first to the left, then to the right, passing back through the starting point every two seconds as the undulations increased in amplitude (the degree of displacement from the center). The buildings and houses and structures of Mexico City followed, their foundations moving in the same directions on the same time scale, the upper levels of multistory structures following, but just a bit behind their foundations as the structures of the buildings themselves flexed and bent, protesting the sudden movements. In buildings on bedrock (the majority of the city) the structures moved with enough acceleration to knock over filing cabinets and empty shelves, shuttling tables and chairs and other furniture across thousands of rooms—but the structures themselves remained intact. But the buildings whose foundations sat on the ancient bed of Lake Texcoco were feeling something different. Within ten seconds of the first S wave arrivals, those structures began to come alive, swaying with the rhythm of the quake, the upper stories of buildings up to fifteen stories high rumbling to the limits of a cycle to the left just as the foundation began traveling back to the right, each cycle building the amount of displacement.

  Within seconds of their arrival the two-second-cycle seismic waves had begun to vibrate the spongy clay of Lake Texcoco’s dry lake bed first to one side, then to the other—back and forth—each cycle causing greater side-to-side undulation of the resilient mass like Jell-O, responding to a shaken bowl with increasingly violent wobbles. With each cycle the alluvial Jell-O amplified the waves even more, transferring that amplified motion to the foundations of the buildings on its surface, those foundations in turn whipping the upper levels of multistory buildings back and forth, each cycle increasing the displacement like the increasing arc of a child on a swing set going farther and farther from the vertical position but powered only by a gentle nudge from someone on the ground at the start of each cycle—a phenomenon known as resonant motion.

  In the first thirty seconds, hundreds of reinforced concrete buildings took the frightening undulations in stride, walls breaking and buckling, concrete cracking around joints where floors were attached and walls were bonded, but holding together with the glue of a thousand steel reinforcing rods embedded in the poured concrete. In buildings such as the Hospital Juárez where nearly a thousand patients and staff had been panicked by the first violent undulations) each floor was a heavy slab of steel-reinforced concrete supported by slim columns also of reinforced concrete—the reinforcing rods welded together haphazardly throughout the structure. The building might end up fatally damaged, but at least in theory the strengthening would keep it from collapsing. Most contemporary buildings had been designed (and supposedly built) to meet Mexico City’s stringent earthquake building code standards, but those were standards which called for the ability to withstand ground shaking only one-quarter as severe as that which had begun to happen to the structures of the southeastern section of the city.2

  And as the hospital—along with hundreds of other buildings like it began to accelerate with each sideways
lurch, a second snag on the southeastern end of the Michoacán gap fragmented, some twenty-six seconds after the first (at 7:18:14). An adjacent section consisting of hundreds of square miles of rock surfaces twelve miles deep rumbled past each other, radiating out more waves of many wavelengths—but especially the same monstrous pulses in the two-second range—additional pulses which bore in on Mexico City at eighty-eight hundred miles per hour, arriving just as the first-wave trains were diminishing, picking up the undulations of the lake bed and the buildings on top of it where the other had left off, whipping the foundations of buildings which had started with a natural resonant frequency of less than two-second cycles, but which had loosened up with fragmenting walls and breaking joints, their resonant frequency increased now into the same range as the worst of the waves undulating the alluvial muds.

  And with fewer than sixty seconds of shaking past, the reinforced concrete buildings of Mexico City which stood between seven and fifteen stories high began to tear themselves apart.

  Dr. José Hernández Cruz, an intern at the twenty-five-year-old Hospital Juárez, had joined five other doctors in laughing at the startled looks on the faces of his patients in the orthopedic ward when the building began to move. Moment by moment, however, the motions had become more violent, canceling the laughter, drawing veils of serious apprehension over the faces of the medical men as they listened to the sounds of a thousand items hitting the floor, the roaring and squealing of concrete and steel being forced into motions never contemplated by the design. The entire building would accelerate to one side, taking everything and everybody with it until building and occupants all had reached the same lateral speed—at which point the hospital would suddenly stop and reverse direction, leaving the people, the beds, the furniture, and anything else loose crashing toward the walls as the hospital began accelerating in the opposite direction. With each cycle the force of the reversals became greater, and it became obvious from the horrendous noise that the building couldn’t take this for long.

  Suddenly there was an absence of light, accompanied by a horrible sinking sensation amidst unbelievable noise and dust and thundering motion as something hit the doctor on the head, forcing him down in a microsecond on top of one of his colleagues. Several blocks away hundreds of people in the Nuevo León apartment complex (fifteen stories, three wings, four hundred units) had felt the same motion, as had the occupants of the huge Hotel Rágis. Floor by floor the various structures pancaked, leaned, and crumbled, hundreds of tons of concrete and steel rubble crushing many of those within, trapping many others deep inside spaces barely high enough to survive—spaces which moments before had been rooms eight feet high.

  The motion continued, but the world was pitch-black, filled with choking dust and strange odors of spilled liquids and gas. Dr. Cruz realized that the doctor beneath him was not breathing, and that he was trapped—pinned by wreckage, cut off from light, and obviously in mortal danger. Exactly how bad it was, he didn’t know, but the fact that the orthopedic ward had collapsed was as obvious as the fact that he physically could not move.

  But the sounds from all around him were more chilling than his own worries for safety. There were cries of terror and moans of pain, and chilling screams from the trapped, the hurt, and the dying. Sounds from fellow humans entombed in a district of heavy wreckage which in the space of three minutes had taken more than five thousand lives—a toll which would increase as the hours to come ticked by.

  Her reporter companion had grown quiet for a while as they reached the lower levels of the mountains, still seventy miles or more from the coast. Karen McNally’s mind had begun to race past her growing fatigue into a host of subjects: the task which lay ahead of placing the portable seismographs; the logistics problems of getting the team fed and bedded down later on; and the hope that any more serious aftershocks would have the courtesy to wait for her seismograph network to be installed and activated. Other members of her University of California at Santa Cruz team had left for Mexico within twelve hours of the quake. Karen had departed a day later, on Friday. All of them were to rendezvous on the coast on Tuesday after installing the portable network. In the meantime, there would be nonstop, backbreaking effort required if they were to capture more of the telltale signatures of this subduction zone.

  There were so many overtones from past, last-minute expeditions—unexpected phone calls followed by sudden scrambles to field a team of experts in search of aftershocks. The Coalinga earthquake two years before, for instance, also had been a rushed affair—and a fascinating one. The remembrance of that late-night trek into very familiar territory was quite a contrast to the current one: racing through the wilderness of rural Mexico in the middle of a tropical night.

  Karen had grown up in California’s San Joaquin Valley, adjacent to the town of Coalinga. Her father, who had really expected his firstborn to be a son, had ideas and plans of what a father and son would do together when Karen had arrived. The realities of the business world and the working world were things he wanted to teach his heir. When he found himself with a smart and energetic daughter instead, the highly educated inventor and manufacturer of farm machinery had decided to keep the same script, and Karen was treated accordingly. A childhood replete with hard work and early responsibility coupled with expectations for superior achievement in a happy family environment was the result. She had driven a tractor by age three (and been run over by one, escaping uninjured, by age five). She had helped with her father’s business, and she had traveled with him many, many times through the rural fields and farms of the San Joaquin, her mind etching the sights and the smells of the fertile farmland and the adjacent oilfields of Coalinga along with the memories of her father’s endless negotiations and conversations with the farmers who owned and tilled the land. She knew the people, she knew their temperament and their outlooks and their hopes and dreams, and she had experienced a profound feeling of déjà vu to be back among the same farms and fields as they had approached Coalinga in the predawn hours following the 1983 earthquake.

  The subsequent days of dealing with those same farmers, gaining permission to install seismographs, asking questions about the earthquake, and keeping an exhausting schedule as the aftershocks continued to rock the shattered town, had been a combination of pleasant memories and confusion. Her father had expected her to be a doctor, an M.D. who might, perhaps, return to the valley to practice as a country physician someday. She had always thought being a doctor meant earning a Ph.D. as a scientist, and seismology had been her ultimate interest. As a seismologist, however, Karen McNally had somehow never expected to “practice” near her childhood home. Coalinga’s agony and the ensuing weeks of field research had changed that.

  And Coalinga had changed something else. Not that she had been smug about the abilities she and her colleagues had acquired to identify seismic gaps and pinpoint the locations of upcoming earthquakes, but the sudden eruption of seismic energy from two previously unknown faults (eventually identified and mapped by Karen and others from the aftershock seismograms) had been a warning against smugness. No one had known that those faults lurked beneath the Coalinga oilfield. No one had suspected. Yes, they had come very far in understanding the earthquake mechanisms and identifying potential hazards, but it was painfully obvious that it was only the beginning. Decades of expensive research efforts were vital. Even on the West Coast, it seemed, there were many seismically active cracks beneath the surface which no one had yet discovered, and to that extent, Coalinga had been a profoundly disturbing reminder of how far her science had to go, and of how much there was ahead to discover. It was a feeling and an excitement she tried to convey to her students as a professor, a belief that any of them could make a profound difference in advancing our knowledge and our ability to keep earthquakes from being the killers that this current monster in Mexico City was turning out to be.

  They were within fifty miles of the Michoacán coastline now, almost to the area where the first portable seismograph sh
ould be placed amidst jungle grasses in the sweltering temperatures and sopping humidity. Karen chuckled quietly at the fact that her resident reporter was going to have to earn his keep. Like it or not, David Smollar was going to be lugging heavy car batteries and other equipment into the jungle in an hour with the rest of them.

  Small clouds of mist passed into and beyond her headlights as she thought about the next moves, and about what was going on back in the Mexican capital. Karen was acutely aware that hundreds—perhaps thousands—of fellow humans lay trapped and dying beneath tons of crumbled building materials in the Mexican capital city some two hundred miles to the east of her. There had been a massive aftershock on Friday—an Ms 7.6 monster which hit the city at the exact moment she was standing in the terminal at Los Angeles International Airport telling David Smollar that such an aftershock might be imminent.

  In Mexico City the shifting rubble and precarious structures of critically damaged buildings had collapsed further, extinguished more lives, including those of many trapped people who had been hanging on by a thread of hope and prayer since Thursday morning, many of them deep within the artificial tomb which so many downtown buildings had become. But there were many hearts still beating under the tons of rubble. Karen and the other members of the team, especially those from Mexico City, had heard much of the rescue efforts while they worked feverishly in Guadalajara, preparing for this dash to the sea. Obviously some people would be pulled out in time, and some would not. The television clips of the pancaked horror that had been the Benito Juárez Hospital, for instance, made that reality all too clear. The citywide death toll was already estimated at near ten thousand people, with thirty thousand injured, more than a hundred thousand homeless, and more than seven thousand buildings badly damaged or destroyed. And that toll was likely to grow—especially if more major aftershocks hit the municipality.

 

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