A Crack in the Edge of the World (21 page)

Nowhere is this more visibly true today than along the 750 miles of the San Andreas Fault, at the very western edge of the North American Plate, where it meets up with its neighbor plate that underlies the Pacific. The San Andreas Fault is young by the standards of the West, and very young by the standards of geology. But it is a very great deal older than America, older than California, and older than San Francisco, and it has been making its own kind of mischief for many millions of years past, and will continue to do so for many millions more to come.

The law against sodomy goes back fourteen
          
hundred years to the Emperor Justinian, who felt
          
that there should be such a law because, as
          
everyone knew, sodomy was the principal cause of
          
earthquakes. “Sodomy” gets them. For elderly,
          
good-hearted audiences, I paraphrase; the word is
          
not used. College groups get a fuller discussion of
          
Justinian and his peculiar law, complete with
          
quotations from Procopius. California audiences
          
living on or near the San Andreas Fault laugh the
          
loudest—and the most nervously. No wonder.

G
ORE
V
IDAL
, Matters of Fact and Fiction,
1977

A
T A QUARTER PAST TEN ON THE MORNING OF SEPTEMBER
28, 2004, a woman named Christy Gieseke was taking a shower on her horse farm in San Miguel, in the vineyard country of central California. Suddenly the house began to shake violently. Ms. Gieseke ran out of the bathroom, noticed that the living-room chandelier was shimmying dramatically on its chains, decided to run, and eventually made it, unscathed, into the open air. Her dog, a usually well-tempered Rhodesian ridgeback, was panicking, running wildly across the yard,
barking madly. But her horses, which she might have supposed would be bucking in panic, were by contrast unusually and strangely quiet—stunned, perhaps, by this inexplicably frightening set of circumstances.

After only a few more seconds, the shuddering, and the barrage of curious creaking and cracking sounds from the very earth itself, came to an abrupt halt. The event was, at least for the time being, quite over. The horses began to graze peacefully once again, pawing the ground with their hooves by way of seeming remonstrance; the chandelier's swaying slowed, then stopped completely; and whatever growling sound had welled up from the ground faded to mere white noise, and then was gone altogether.

It was at this point that Christy Gieseke realized that she had dashed into her garden quite naked but for a dishtowel she had grabbed in the kitchen on the way through. She ran back into the house, found her clothes—and hoped that would be the end of it. Earthquakes tend to make people nervous—and to behave spontaneously, even in a place as accustomed to the earth's violent movements as San Miguel, California, and the rather more notorious neighboring towns of Paso Robles and Parkfield.

This, as the locals like to say, is earthquake country. San Miguel, hilly, pretty, moneyed—horse ranches, wineries, and exemplary weather—suffers from a ceaseless onslaught of small seismic events, to which many of the locals have become almost entirely inured. Once in a while a larger earthquake strikes. The last of major significance hit just before Christmas in 2003; it killed two people in Paso Robles, toppled a church tower there, and did grave damage to the 200-year-old Mission San Miguel nearby.
*

But let us concentrate on the event of September 28. Ms. Gieseke and her horses; a vineyard owner named Harry Miller, who observed
“trees shaking like brooms, and dust coming everywhere,” as 300 cases of wine stored in his cellar were upset and jets of water were sent spouting thirty feet into the air from his tank; and the 9,000 Californians living between Sacramento and Santa Ana who are officially recorded as having felt the event—all were affected by what is now as properly and fully annotated a disturbance of the earth as has ever been known.

Its first shock—the mainshock, as the originating shock of an event is known—struck at 24 seconds past 5:15
P.M
., Coordinated Universal Time, or 24 seconds past 10:15
A.M.
Pacific Daylight Time. The shock produced a strong shaking that lasted for almost exactly 10 seconds, and it was followed by a series of some 161 aftershocks. The event's epicenter—the point on the earth above which the shock-inducing rock rupture occurred—was seven miles southeast of the village of Parkfield. The hypocenter—the subterranean point where the rupture took place—was a little less than five miles down.

Once the rock had ruptured the shocks then traveled, and at a fantastic speed, in a northwesterly direction, disturbing people—Mr. Miller and Ms. Gieseke among them—in the myriad ways that a shock as impressive as this one can. The formal classifying number of the event (or the
eq
, as such happenings are generally known in the seismological community) was NC51147892, with the NC being the internationally recognized two-letter code for the Northern California Regional Seismic Network, based at the U.S. Geological Survey headquarters at Menlo Park, at the upper end of Silicon Valley. The regional moment magnitude of the quake, which is what is usually calculated and released to the press, was 6.0.
*
No one was hurt by it, nor was there any but the most mildly inconvenient damage.

In normal circumstances, and in most places, this would have been a merely moderately significant event. But the circumstances, and the place, were anything but normal—and as it happens, the event of the September 28, 2004, was probably more measured a seismic happening
than had ever been recorded in the history of this planet. And that is because the event took place very close to this otherwise memorably forgettable little Californian settlement named Parkfield.

Parkfield, California—a sleepy, dusty farming town that nestles among rolling hills fifteen miles to the northeast of Christy Gieseke's home—enjoys a peculiar reputation in world seismic lore. It may not suffer most from a superabundance of seismic activity—that record, for what it is worth, appears to be held by a faraway and rather tumbledown Californian village called Petrolia, which has earthquakes almost every other hour—but it is the place that suffers most from a superabundance of seismic science. For it has had so very many measurable earthquakes (dozens of very small ones every week, and larger tremors that are substantial enough to be felt by reasonably aware humans several times a year, and those of a magnitude to drive women from their showers every two or three decades) that in the last years of the twentieth century a program was begun that made sure that every Parkfield hillside and valley and suspicious-looking outcrop or knoll or riverbed was covered with an array of earthquake-detecting instruments. These have become more sophisticated, delicate, and expensive as the years and science have worn on.

Anyone who makes it to this tiny town rapidly becomes aware that it is a much-measured place. Beside the roads, up on the hilltops, lurking in groves of trees, and in strange boxes with menacing locks and orange notices that warn of the not-so-dire federal penalties awaiting those who interfere, are the devices that monitor, hour by hour and, in some cases, millisecond by millisecond, what happens below the earth around Parkfield. A photocopied guide handed to visitors relates the kind of thing: “on your right, look for a 4' X 4' X 4' structure … this contains a seismometer,” “on the south side of the road there is a piece of PVC pipe sticking out of the ground with the letters
JPL
-
GPS
—this belong to the Jet Propulsion Lab,” “on the left side is a USGS creep-meter … do not touch the thin metal wire.”

The data from the machines is broadcast to thousands out in the seismically fascinated world. Some is sent via tiny satellite aerials to Colorado, some goes to a university near San Diego, still more to the Geological Survey's regional headquarters at Menlo Park, while other parcels of information are flashed to monitors in Pennsylvania, North Carolina, Oxford, London, and Brisbane. Parkfield may be a town very little known in most of the rest of lay California, but to members of the geological priesthood with a keen interest in how the world is believed to work, it is the center of the seismic universe.

Though Parkfield is no Grand Canyon, the local residents know they are onto a good thing. So the town's café, across the dusty street from a hotel made of logs, sports a water tower painted with the slogan
BE HERE WHEN IT HAPPENS
, and the hotel tries to tempt passersby with
SLEEP HERE WHEN IT HAPPENS
. On the menu is a steak called the Big One, as well as a rather more modest version called the Magnitude Six; and the desserts are called Aftershocks. A sign nailed to a tree offers eggs produced by an evidently surprised chicken shown being shaken awake; and there are a handful of memorials and notices and walking trails that remind people of the dramatic moments to which this town is prone.

At the southern entrance to Parkfield is a white-painted iron highway bridge that takes the road across the oak-shaded and occasional stream known as the Cholame Creek. Anyone crossing the bridge will notice that it is spectacularly bent: The metal rails and supports all veer off to the right by well over a foot and a half. Moreover, there are patches of freshish asphalt on the pavement, where repairs have been made by CalTrans, the authority that fixes damaged state roads, and whose crews doubtless sigh whenever they hear of fresh earthquake activity up at Parkfield. The event that pitched Ms. Gieseke from her shower moved large chunks of concrete off their foundations and opened up a new gap several inches wide. For a time the bridge was closed, yet again, while the asphalters did their stuff. By measuring the bridge—and people have been doing this for many years, especially since it was particularly badly damaged by an earthquake in 1966—it can be shown that the abutments have moved more than five feet since the structure was built in 1936: The westernmost abutment, the side farthest away from Parkfield, has moved to the north, while the side closer to town has slid down toward the south.

The little iron bridge and the half-dry creek serve as all-too-visible reminders of just why it is that Parkfield occupies the place that it does in the seismic canon. For the creek marks the very edge of the North American tectonic plate, and is the center of the narrow zone that shows where the next-door Pacific tectonic plate butts up against it, and lurches and slides northward along it with predictable unpredictability.

SOME CHAPTERS BACK
we began a long journey clear across the full expanse of the North American Plate. It was a journey that started in a valley in the center of Iceland, where a line of cliffs marks the plate's far eastern edge. Here, in the middle of this very ordinary-looking Parkfield town bridge, is the point that marks its extreme end—the plate's western edge, where it rubs against its Pacific neighbor. Central Iceland is divided from central California by 6,000 miles—a distance that marks, at this place in the world, the width of the entirety of one of the greatest and most important geological entities of all.

THE ABUTMENT
of the bridge that stands closer to Parkfield is on the massive North American Plate; the abutment on the other end stands on the Pacific Plate, the equally massive and ever-moving part of the world that underlies such faraway places as Hawaii and Tonga, Pitcairn Island, Easter Island, and the South Island of New Zealand. Another part of the world begins right here. And the line that divides the two plates, the place that geologists like to call the plate abutment, or the plate boundary, coincides with the visible surface manifestation of what is perhaps the best-known geological fault that can be seen anywhere.

The line is some 750 miles long. It curves sinuously, in the shape of an elongated boomerang, from where it makes its landfall on an unstable clifftop up in Humboldt County, in the wet and windy north of California, to where it dives into the heart of the earth in a hot and muddy field beside a hissing geothermal plant, down by the fences and well-armed border guards at the Mexican frontier. The town of Parkfield lies almost halfway along the line; the buckled bridge is buckled because although it, too, is sited
on
the fault, it cannot be said to lie
along
it, but rather to lie
across
it, since the road in and out of Parkfield needed to cross from one side to the other. And it is axiomatic that any structure that is built across a fault like this is placed under enormous stress whenever the fault moves—something that this one does, uniquely, all the time.

Shifting, sliding, vibration, destruction—everything about this 750-mile-long line suggests that we are dealing with a living, breathing, ever-evolving giant that slumbers lightly under the earth's surface and stirs, dangerously and often, according to its own whims and its own rules. At almost every single place where the line can be traced there is evidence of movement, damage, some kind of mysteriously infuriating life. The bending of the Parkfield bridge is one instance, as is the crumbling instability of the sea cliffs up in Humboldt County where the fault first comes ashore; the regurgitating steam that hisses around that muddy southern field is another, as is every earthquake that is measured every day in the Cholame Valley, like the one that drove Christy Gieseke from her shower in San Miguel, like the one that knocked down the nearby mission some years before, and like hundreds of others besides.

And, while there have been countless other shakings and vibrations randomly scattered across the American West, once a series of systematic studies of California's seismicity had been made a century or so ago, a very obvious pattern soon emerged along this line. There seemed to be much more movement and nuisance of one kind or another along it than anywhere else in the state.