A Crack in the Edge of the World (35 page)

Close modern analyses of the data from all the seismograms show that the earthquake unfolded in a number of stages. All of them are now known to have begun at a point rather less than ten miles south-southwest of where Officer Cook was standing at the eastern end of San Francisco's Washington Street, several miles down in the earth's crust at a site that lies well beneath the Pacific Ocean.

Modern analyses of the information have produced a different set of results from those computed at the time. The very distant seismogram information was not fully appreciated in the months and years that immediately followed the earthquake. It was seen more as a curiosity, as a series of unanticipated confirmations of the event's sheer power. The thinking at the time held that the quake's origins should be deduced from a small number of local recording stations. The more distant records might be impressive, but they were perhaps not truly to be trusted.

Since the recorded time of the shock waves' arrival is crucial to finding out where the earthquake happened, the Lawson team became obsessively concerned with determining exactly when the event was felt, detected, and recorded in places very close indeed to its supposed point of origin. Buried deep within the commission's great report are interviews galore with those who felt and recorded the two most distinct phenomena of the earthquake: the onset of the first perceptible vibrations, and the arrival of the truly great and destructive shock. Typical of the reports that Lawson collected is one from a Professor T. J. J. See,
*
the appropriately named director of the (equally appropriately named) Mare Island Naval Observatory on San Pablo Bay:

I had been sleeping downstairs, lying with my head to an open window, which faced the south, and as the house was not seriously endangered at any time I was favorably situated for making careful observations of the entire disturbance. I had been awake some time before the earthquake began and, as everything was very quiet, easily felt and immediately recognized the beginning of the preliminary tremors.

The exact time of the phenomenon
. This was found by the stopping of two of the four astronomical clocks at the Observatory. The violent shocks were so extreme that the pendulums were thrown over the ledges which carry the register for measuring the amplitude of the swing. The standard mean time thus automatically recorded was: by the mean time transmitter 5h 12m 36s; by the sidereal clock 5h 12m 35s. The yard clock at the gate, which is simply an office clock, though electrically corrected from the Observatory daily, and therefore approximately correct, gave the time as 5h 12m 33s. The agreement of all these clocks is very good; but I think the best time is the mean of the two astronomical clocks, viz 5h 12m 36s. I estimate that the error of this time will not exceed about 1 second.

Thus were the rigorous minds of science applied to this one small problem of when the quake occurred—because it was realized that by knowing
when
, they could work out
where
. So an obsessive, super-pedantic dedication to precision, similar to that of Professor See's, seems to have informed all of Andrew Lawson's witnesses—such that in the end, and without fanfare, he was able to announce his own considered view of when the shocks first began, and when the biggest of all the shocks occurred, and where these two events had their origins.

He crunched all the data from four close-in observing stations—Mare Island, of course; George Davidson's observations at his home in Lafayette Park, San Francisco (an account of which is in the prologue); the Students Astronomical Observatory at Berkeley; and the Lick Observatory at the top of Mount Hamilton near San Jose—and from one rather distant site, the International Latitude Station
*
in the town of Ukiah, about eighty miles north of the city.

From all of this data he was able to declare, definitively, that the shock began at 11 minutes and 58 seconds after 13 hours, Greenwich Mean Time (GMT)—in other words, two seconds before 5:12
A.M
., Pacific Time, plus or minus three seconds. The place where this opening salvo was triggered was computed to be under the sea, just a short distance off the Golden Gate. And the depth of the vibrations' beginnings—all computed from the simple geometries of the observations from these five sites—was about twelve miles, give or take about six.

And then there was the biggest shock—the terrifying “second shock” that so many of the observers could not fail to notice, whether they were rocked softly in their beds far away up in Oregon, or down in Anaheim, or over in Winnemucca, Nevada, or whether they were knocked flat by it in San Francisco, Santa Rosa, or San Jose. According to Lawson, it came exactly thirty seconds later, at 13h 12m 28s GMT, or at twenty-eight seconds after 5:12
A.M.
, Pacific Time. This shock, he went on to say, took place somewhere between the surface and twelve miles down, and at a spot close to the village of Olema, which has long considered itself—wrongly—to have been the earthquake's epicenter (and where the locals, somewhat shiftily, still peddle hats and T-shirts to try to underline the point).

Olema was the place where, from the evidence of broken fences and torn-up roads and ruined barns—it appears that the surface of the earth was ruptured to a greater extent than anywhere else along the entire fault trace—as much as twenty-one feet. This was a pleasing happenstance for the scientists, because they were able to see that their calculations proved—or so they thought—that the most violent shock took place just below the point where the earth itself was most dramatically torn apart.

As it happens, Lawson and his fellow researchers were quite wrong—understandably so, given the paucity of the information they chose to examine. Had they looked closely at the entire seismic record they had available to them, and been inclined to focus on the data they had collected from all the other ninety-six seismographs, then they might have been able to make a more accurate fix. But there was a problem, in that they were not necessarily fully aware of what it was exactly that they were
seeing
in all of these records. In those seismically unsophisticated years some of the records must have seemed little more than runes or hieroglyphs or impenetrable codes. Only recently has the science advanced to the point where the records, combined with the anecdotes and the records of earth movement, can be annealed into a comprehensible whole. And from all this has now emerged a rather better understanding of just what took place beneath the ground on that fateful morning.

Specifically, and as already noted, the place where it all began is now known to have been just a few cables northwest of the tiny guanocrusted island of Mussel Rock, off what were in the early years of the century thousands of acres of empty and open grasslands, with clifftop meadows dotted with dairy cows. The channel between the island and the mainland marks where the San Andreas Fault passes by: The island stands on the Pacific Tectonic Plate, and the mainland on its North American opposite number. The fault that divides them is the line along which the Pacific Plate moves, northward, by as much as thirty-five millimeters, one and a half inches, every year.

And at 5:12
A.M.
that day, along that very line, just a few hundred yards off the island and some miles down deep within the zone of crushed rock where the rocks had been grinding together for decades, something suddenly gave.

With a lurch, the pent-up energy of all the years when the Pacific Plate (on which Mussel Rock stood) had been moving northward past the North American Plate (on which the grasslands, meadows, and cows all stood), was instantaneously released, and a foreshock, like a sudden ignition of a pile of explosives, vibrated out and through the rocks, causing the entire area's underneath to pulsate in a huge, sonorous, basso profundo roar. That was what the policeman heard: The announcement of the foreshock, the enormous snapping sound of the rocks at the hypocenter breaking, lurching forward, and suddenly setting themselves free.

Once free, they moved. The pent-up forces that had held the Pacific Plate static for the better part of the previous two centuries were unleashed. The elastic rebound was now free to occur, and it did so in a jolt that some calculate as moving northward and southward at two miles a second. The rocks lying above the Pacific Plate then shifted, some of them by scores of feet. The vibration caused by this motion spread outward like a ship's bow wave, and it set the earth above the north-shifting plate rearing up and outward, rippling and bucking just as Officer Cook had reported. It spread outward in different ways, depending on the nature of the rocks through which it spread: Sometimes it moved slowly and trembled fairly minimally; at other places it shot out with terrifying speed and caused immense rocking and crashing, which triggered immense destruction. Sites like Olema, where the quake seemed to go especially wild, are known as asperities—patches of geological roughness that corrupt the otherwise smooth progress of the outbound shock waves.
*

All of a sudden the inches-a-year motion of the plate that had been locked for so long was suddenly translated into something much, much, faster: A ripping, tearing movement that was unimaginably fast, as though a glacier had suddenly superheated and been turned in an instant from solid ice into a raging flume of water. The huge bow wave of shock and motion spread up and down the city, up and down the state, roaring along at 7,000 miles an hour, and affecting ever more northerly and southerly towns and villages as they appeared on each side of the spreading rupture in the surface.

One by one the streets of San Francisco rose and fell under the influence of the spreading wave; and one by one the nearby towns and villages were affected and afflicted too. It was as if a plowshare were being driven through their countryside, with the soil on each side of the blade turned up and over, carrying all before it and tossing it contemptuously to each side.

On the western side of the fault rupture, all of this motion occurred beneath the waters of the Pacific—at least, it did where the fault ran close to the ocean, or ran below it, as it did near San Francisco. On the eastern side, however, the bow wave roared beneath the land, passing through houses and streets, across roads and bridges and railway lines, through fields, farms, and fences, and tearing through hamlets, villages, towns, and cities, without care or interruption, and leaving the most terrible and unforgettable damage and destruction in its wake.

The disturbance lasted 48 seconds. On looking from the window of our hotel, which was badly shattered—two men in fact to right and left of our rooms were killed—I saw the whole City enveloped in a pile of dust caused by falling buildings.

From a diplomatic telegram sent on April 25, 1906, from
S
IR
C
OURTNEY
B
ENNETT
, His Britannic Majesty's Consul-General,
San Francisco, to Sir Edward Grey, Bart., &c., &c.,
Secretary of State for Foreign and Colonial Affairs, London

Official pronouncements from the governments of the world's great cities are documents seldom marked by excess of any kind, and, being written by bureaucrats, are rarely colored by sentiment, hyperbole, or dash. But the Municipal Report of the City of San Francisco for 1907, published by the city's Board of Supervisors—as the law required it to be, each year—has a power and pathos all its own. Paragraph by paragraph, the book-length report recounts the ruin of the great metropolis in tones of unrelieved and detached misery, culminating in a single haunting sentence: “The greatest destruction of wealth created by human hands was that which resulted from the fire which occurred in San Francisco on April 18, 1906, and the three days succeeding.”

Whenever one considers the earthquake that resulted from the rupture of the San Andreas Fault that April morning, one must take into account what followed almost immediately after the trembling of the ground had stopped—and that was a quite astonishingly destructive and long-lived fire. The two calamities have since been almost inextricably linked as the “San Francisco Earthquake and Fire,” and the conflation of the two events has, so far as narrative and investigation is concerned, made for both convenience and confusion.

So when fatalities are spoken of, we have to ask: Did they die as a result of the quake, or in the subsequent blaze? Or when we refer to structural damage: Were the buildings destroyed because of the shaking or because of the fire? Many made much of what could have been a rather fine distinction—not least the insurers, some more eager than others to weasel out of their contractual responsibilities, their obligations to pay up. On all too many occasions homeowners would be icily informed that the damage their particular house had sustained had been due to the earthquake—against which,
with profound regret, but do please read the fine print
—they had not been insured. On the other hand the fire against which they
were
financially protected had arrived some hours later, laying waste to what was an already injured and uninsured—and hence suddenly quite valueless—building. And thus, from the insurance point of view, it was all bad news, and such
hard luck
. There would, thanks to this fine distinction, be no payment.

The simplest way to examine the physical damage caused by the ground shaking is to chronicle the destruction suffered by communities where fire was not so great a factor—at Stanford University, for example, where spectacular harm was done to the newly built university,
*
all of it very evidently wrought by the shaking of the ground, and yet without a single flame to add confusion or misery to the scene. But up in San Francisco it is well nigh impossible—except later, and forensically—to separate the two events. So it is perhaps best to rationalize this by accepting that everything—the earthquake, all the consequent destruction, all the death, and the outbreak of all the all-consuming fires—had as its ultimate cause the movement and the ground rupture from the fault. The earthquake shook the ground, it broke the buildings, it killed and maimed, and it spawned the fire.