Cascadia's Fault (6 page)

Bakun's coauthor in the prediction study, seismologist Allan Lindh, told us they were studying a stretch of the San Andreas near the farming town of Parkfield, California, that had ruptured five times since 1857—each event a magnitude 6 temblor that seemed nearly identical to the one that came before, as if the same punch were being thrown over and over again. Bakun and Lindh had convinced themselves the next in this series of “characteristic earthquakes” was due in about three years. According to their calculations, the fault would build up enough stress to break again as early as January 1988.

In August 1985, only a few months before our visit, Bakun and Lindh published the first official seismic prediction ever issued by the USGS: “The next characteristic Parkfield earthquake should occur before 1993.” Even with a five-year fudge factor, they had stuck their necks out by putting the prediction in writing in
Science,
one of the most prestigious and high-profile research publications in the world.

Like Bakun, Lindh seemed to be a cautious man. Still, there was enthusiasm in his voice as he talked about trying to trim the fudge
factor and “narrow down the time from a few years to months, to a few days.” He told us, “I think we've got a fighting chance,” asserting that the way to refine the prediction was to concentrate as many instruments as possible along one small segment of the fault—the same fifteen-mile (25 km) rupture zone that had moved in each of the previous Parkfield punches—and monitor every little creep and twitch in the earth, day and night, until the next rupture. With luck, they might spot some kind of precursor that would allow them to issue a warning to the public.

When we wrapped the USGS shoot late that afternoon, my team and I drove four hours south on Highway 101 from Menlo Park, through the rush hour of San José, to a wine-country town called Paso Robles, where we spent the night. Early next morning we headed east into ranch country across dry brown hills on bumpy two-lane blacktop in search of a wide spot in the road called Parkfield. Our map showed it smack in the middle of nowhere about halfway between San Francisco and Los Angeles.

Roughly thirty miles (50 km) east from Paso Robles we passed a road sign that told us we had found what we were looking for. Parkfield had a population of thirty-four, not counting cattle, and stood 1,520 feet (463 m) above sea level. We pulled up in front of what looked like an old ranch house made of square-cut timbers the color of creosote with a wide veranda, a corrugated metal roof, and a big stone chimney. Out front, in a tidy patch of unnaturally green grass, stood a tall wooden cowboy carved from a log and bolted to a stump with a small wooden dog at his knee.

In a gravel parking lot stood the rusty iron hulk of what used to be a water tower. In a curvy flourish of creamy white letters, a hand-painted sign read “The Parkfield Cafe.” Under that, in slightly smaller print, was the proclamation “Earthquake Capital of the World. Be Here When It Happens.”

Farther down the road we found the man we were looking for. USGS technician Rich Lichtie was waiting for us beneath a one-lane
bridge that spanned a gully where Little Cholame Creek trickled west toward the sea. Lichtie fit the landscape in his baseball cap, blue chambray work shirt, jeans, and cowboy boots. His windburned complexion and red walrus moustache allowed him to blend in with the surroundings even better. No labcoated scientist from the big city, Lichtie was the guy in charge of all the USGS equipment that was jammed into the ground along both sides of the fault, and he clearly spent a lot of his time outdoors.

Of all the places he might have arranged to meet us, he had chosen this bridge for a reason and wanted us to see it from below. So we unpacked our gear and trudged down into the gully for a closer look. That's when Lichtie explained that this big ditch was part of the San Andreas, that the bridge literally crossed the fault, and that the last Parkfield event, back in 1966, had torn the old bridge off its foundations.

We were looking at a replacement span that already showed signs of stress. Doug, my cameraman, got a telling close-up of one big bolt holding two heavy steel girders together by no more than a few threads. The two main sections of bridge deck had already been pried apart far enough for sunshine to burn through a gap between the beams. It was a crude yet graphic display of creep along the fault.

Lichtie took us up the road to a cow pasture, where we hiked across the dun-colored grass toward a dry gulch with a storm culvert dug vertically into the earth. When he removed the cover, we could see a metal platform bolted to the corrugated wall of the culvert with a cable-and-drum contraption that looked like something a kid might build with an erector set.

Halfway down the culvert was a circular hole cut into the earth several feet below the surface, where a horizontal plastic drainpipe extended toward the far side of the gulch. Inside the pipe was a pencil-thick braided steel cable that looked like a buried trip wire. Lichtie called it a creepmeter and explained that it was pretty much what it looked like—a wire sixty-five feet (20 m) long, stretched across the
fault and connected to a strain gauge (in a toolbox at the bottom of the culvert) capable of measuring even a few fractions of an inch of slip along the plates.

Next Lichtie took us to a nondescript shed in a grove of walnut trees, halfway up the side of the gulch. When he unlocked the door we saw what looked like a high-end amateur telescope, with a white steel barrel the size of a small cannon, mounted on a high-tech tripod anchored to a concrete pad with a small spotting scope bolted on top like a rifle sight. He switched on the power and a cherry-red laser shot a beam across the valley toward another tiny shack so far in the distance we could see only a smudge through waves of dusty heat rising in the noonday sun.

Lichtie used the rifle scope to line up the laser with a parabolic reflector in the other little shed three miles (5 km) away. “We're shooting the beam across the fault to a reflector, which brings it back here. And we can measure to within a half a millimeter how far that reflector has changed in relation to this building,” said Lichtie. As expected, the laser device had already documented right-lateral motion along the fault—the Pacific plate creeping north toward Alaska.

As part of Bakun and Lindh's experiment, the USGS was in the process of installing a cluster of these and other instruments at various points along the fifteen-mile (25 km) rupture zone in Parkfield. The data were being beamed continuously by microwave to a real-time processor in Menlo Park, where members of the research team were keeping constant watch. They even wore pagers that would wake them in the dead of night or ruin a perfectly good dinner if the fault started to creep or warp or bend itself out of shape.

When producer David Kaufman and I realized the fault ran right up the middle of this gulch, it was impossible to resist the temptation to straddle the fracture and take a picture. Not that you could really see a crack or crevice in the ground; there was nothing more to look at than the V-shaped bottom of this little gully, swathed in straw-colored pasture grass in dire need of rain.

A better way to see the fault was from the air. Aerial pictures showed that one side of the fault had been thrust up slightly higher than the other side, enough to cast a distinct line of dark shadows that ran for miles and miles in the early morning light. There it was, plain as day—two tectonic plates grinding past each other at the blistering speed of two inches (5 cm) per year, roughly the same speed as your fingernails grow.

Far above the valley floor, it was also easier to see why the prediction experiment was being conducted along this particular segment of the fault. The San Andreas is not a straight line. Far from it, especially in Parkfield, where the shadow line zigzags ever so slightly and in a stretch northwest of town actually kinks. There's a five-degree bend along a segment 1.2 miles (2 km) long that was the epicenter of the 1966 quake.

In their paper, Bakun and Lindh referred to this as a “geometric discontinuity” and suggested the bend probably controls how much of the fault moves when it ruptures. I imagined it as a kind of plug or doorstop jammed in the crack, causing the fault to slow down or temporarily stop moving. Not only that, with all this zigzagging, there are rough patches in the rocks—seismologists refer to these as asperities—that create friction and also slow the creeping motion along the fault. While the rest of the San Andreas is ripping along at almost 2 inches (5 cm) per year, the Parkfield segment is lagging behind at only 1.4 inches (3.5 cm) per year.

With tectonic plates as big as these, however, it's obvious the little snags—those Parkfield asperities—can't hold up progress forever. The stress builds to a point where the rocks fail. The rough spots finally shear away. In the span of less than a minute, roughly twenty-two years of “lost motion” along the fault is recovered as the Parkfield segment catches up with the rest of the San Andreas in a shuddering leap to the north. An earthquake.

Another important reason for clustering so many instruments here is that just before the 1966 main shock, the earth may have given off subtle warning signs. Twelve days before the temblor, fresh cracks
appeared in the ground near the center of the rupture zone. Nine hours before the main shock, an irrigation pipe that crossed the fault broke and separated. Were these true precursors? Maybe. That was still the subject of vigorous scientific debate. But even the outside chance of a successful prediction was enough to motivate the USGS team to do everything they could to spot reliable symptoms of the next San Andreas quake.

CHAPTER 3

The Alaska Megathrust: Cascadia's Northern Cousin

Even before the earth hammered Mexico City there were telltale signs of what to expect from Cascadia's fault. One of the first clues arrived by sea at ten minutes past midnight on Good Friday, March 27, 1964. A tumbling ball of water moving southbound from Alaska at an estimated 330 miles (530 km) per hour passed beneath the hulls of ships at sea without causing a stir.

At surface level in the open ocean, it felt like just another swell in the North Pacific. But this was a “seismic sea wave,” what used to be called a tidal wave (now known as a tsunami) and it was very different from the chop and rollers left by a storm that had passed through a few days earlier. To a sailor's wary eye, only the three-foot (1 m) crown of this monster's head would have been visible that night, just another hump in a sea of thousands, with all its furious strength hiding in darkness below.

Unlike ripples, whitecaps, and windblown breakers that churn only the surface, this rolling mountain of brine reached all the way to the ocean floor and traveled at the speed of an airliner. When it reached the western side of Vancouver Island, the front of the wave began to slow
as it scraped over the shallow bottom of the continental shelf, forcing the back half to mound up eight feet (2.4 m) above a normal high tide. An edge of the wave then sheared away and made a fast left turn into a fjord called the Alberni Inlet.

As the turning flood crashed over rocks at the Bamfield lighthouse on the outer coast, a keeper on duty grabbed the phone and placed an urgent call to Port Alberni, a mill town at the head of the inlet. The funnel shape of the inlet itself—a saltwater canyon cut through narrowing mountain walls—squeezed and amplified the wave as it shot toward the heart of Vancouver Island like a cannon ball. The fast-rising swell ran forty miles (65 km) from the Bamfield light to the head of the fjord in only ten minutes, not nearly enough time to spread the word. Port Alberni might as well have had a bull's-eye painted across its industrial docks, marinas, and low-lying residential streets.

No one noticed the fist of frigid seawater as it lifted two channel marker buoys and thundered across the threshold of the inner harbor. Night shift longshoremen, completely unaware, continued to hoist and sling bundles of lumber aboard the
Meishusan Maru,
a Japanese freighter at the sawmill dock. In the nearby pulp mill, boilers were running full steam. Paper machines were spinning out massive rolls of newsprint for the
Los Angeles Times.

With little to do after midnight, most people in this town of seventeen thousand had already gone to bed. Only a handful heard skimpy stories on the late night news about an earthquake that had rattled Anchorage 1,120 miles (1,800 km) away. Even those who did hear about the jolt up north would never guess what was about to happen in the Alberni Valley or how it was connected to Alaska.

Crossing the harbor at 240 miles (386 km) per hour, the tsunami surged beneath acres of floating logs, breaking boom chains, snapping steel cables, and scattering dozens of rafts of heavy timber across the inlet. It assumed the shape of a blitzing storm tide rather than a towering curl. As in Sumatra and Thailand many years later, the wave that
slammed Port Alberni looked more like a river run mad than the perfect breaker that surfers catch only in their wildest dreams.

Minutes later the main water pipeline to the pulp mill broke like a twig. The
Meishusan Maru
rode the surge to the end of her mooring lines, twisted free from the sawmill dock and drifted toward a nearby mud flat. Bundles of lumber floated off the dock and rode the churning froth into downtown streets like so many cubic battering rams. When the leading edge of the drenching brine finally reached the head of the inlet, the last of its energy was spent running upstream against the Somass River. With catlike stealth the water slipped over the low dike along River Road and spilled into the bottom-land housing on the other side.

All these years later it's hard for survivors to recall what they heard first—the mysterious gurgling beneath their floorboards, or the heart-stopping thump of a mill worker's fist against their doors in the dead of night. Allan and Jill Webb lived in one of those houses near River Road. Forty-five years after that Good Friday night, they gathered with other Alberni tsunami veterans in the mayor's office at city hall to recall their experiences. Jill told me it was the awful hammering that she would never forget.