Cascadia's Fault - Jerry Thompson [8]
As Robb lined up his next shot, the ground started to shake violently beneath his feet. At 6:30 p.m., thirty-six hours after the initial shockwave, a magnitude 7.5 aftershock (some experts believe it was another, completely separate earthquake) instantly made a bad situation worse. People who’d counted themselves lucky, who’d thought they had survived the disaster, realized in a heartbeat that it wasn’t over yet. Hundreds ran screaming from homes and apartments in the congested neighborhood surrounding the three towers.
They swarmed across sidewalks and into the streets. Some scrambled into cars and tried to make a getaway, racing toward a nearby freeway on-ramp. “I got shots of everybody running through the streets, trying to get in their cars to drive away,” said Robb, “but it was hopeless.” A torrent of humanity choked the only avenue of escape.
The TV camera was locked on a tripod and the recording deck was connected by a thick black cable, so Robb and Gunter were shackled together. With nowhere to run, they hunkered down, two rocks in a river of terrified people. “It happened so quickly. It’s not like you have any warning.” The more Robb told me the more vividly the scene came back into focus for him. “We were so frightened, we couldn’t even move. I was just weak in the knees.” This from a guy who doesn’t get rattled by much.
Sensing movement over his shoulder, Robb glanced up and saw in a darkening sky that the two remaining towers, thirty stories high, were bending from side to side like tall trees in a wind storm. “When we saw those other two buildings moving back and forth like that, swaying—and you know one had already collapsed—and we were right beside ’em, we figured we were in the wrong place.” But Robb and Gunter were lucky that night. The towers did not fall. And they lived to tell the tale.
Mexico had survived plenty of big earthquakes—forty-two of magnitude 7 or higher in the twentieth century—but nothing as big as the shockwave of September 19 had occurred there in all of recorded history. So geologists immediately started looking for ways to make sense of what had happened. An eerily similar offshore quake had rocked Alaska in 1964. Chile’s 1960 seafloor rupture, at magnitude 9.5, was the largest earthquake ever recorded in the world. In both cases the faults that caused the quakes were impossible to examine, concealed beneath thousands of feet of seawater.
Geologists who’d suggested the Michoacán segment of the Mexican seaboard was somehow a special case—an aseismic zone—were about to face a steep new learning curve. But they weren’t alone. Earth scientists around the world were undergoing a paradigm shift, a fundamental change in thinking about how the planet had formed, how mountains were built, and what makes huge earthquakes happen. For more than three decades, starting in the mid-1950s, much of the conventional wisdom of geology had been debated, updated, and revised by fresh data and new ideas.
By the mid-1960s a new hypothesis called plate tectonics had emerged from the dust of an earlier and much ridiculed theory known as continental drift (more on this later). But in 1985, twenty years after tectonic papers began to appear in the science literature, the idea was still relatively new and more than a little controversial. Not everyone had come to terms yet with the concept of slabs of the earth’s crust, forty to sixty miles (70–100 km) thick, floating around on convection currents of superheated, semi-liquid rock, crashing and grinding against each other, creating jagged mountain ranges like the crumpled fenders of a car wreck, generating giant earthquakes in the process.
Even basic things like the textbook