A Crack in the Edge of the World (34 page)

Although the area where the event was felt was roughly circular, the area where there was real damage was lozenge shaped, with the long axis of the lozenge following, though somewhat unsurprisingly, the San Andreas Fault. So from the outer eastern and undamaged edge in Nevada one has to travel about 300 miles westward, to reach places where the reports of real damage came in. Basically the damage spread through almost every single community between a village called Paicenes in the south and the much more substantial city of Eureka in the north. Not much damage, perhaps—but recordable (and so insurance-claimable) damage nonetheless. Eureka provides a very good example of the kind of edge-of-zone impact that the earthquake had: There were about $5,000 worth of cracked walls and broken windows in town, and the statue of Minerva on the dome of the Humboldt County Courthouse, which had been seen swaying back and forth during the event, finally settled tipped in a southerly position, sloping by 43 degrees.

Closer to the epicenter, more and more of the damage amounted to total ruin; and so, the nearer to San Francisco, there was concomitant mayhem, social dislocation, panic, terror, heroism, and a terrible amount of death. Voltaire's much-derided remark about how knowing all allows one to forgive all springs to mind—though with earthquakes,
as we shall also see later, knowing a great deal about their mechanics does not seem to mitigate their horrors or help us to avoid them.

In the second century of the modern era, when in China it was somewhere near the middle of the Han Dynasty, the astronomer royal to the emperor, a man generally named as Zhang Heng, created an elegantly complicated device known as a
hou fêng di dong yi
, which translates approximately as “earthquake weathercock.”

The original has never been seen, only described. It was a brass vessel, rather like a very large wine jar, that sported on the lip of its upper surface the brass heads of eight dragons, positioned equidistantly around the vessel at the major points of the compass. Each of these dragons held in its mouth—and did so very gingerly, by the points of its teeth—a small ball made of jade. Immediately below each dragon was a toad, its mouth wide open, ready and waiting to catch any ball that might drop from the dragons' dental grasps.

No one knows exactly what was inside the jar, but it is assumed that there was some kind of pendulum attached to eight jointed arms. Everything was arranged with mousetrap delicacy in such a way that if the pendulum swung for any reason, the arm that impeded its swing was moved; this knocked the ball from inside the mouth of the closest dragon and into that of the waiting toad. The instrument, designed to be presented to the emperor and set up by his throne, was for the specific purpose of detecting earthquakes.

The device, which is often displayed today to reinforce the idea that the Chinese were the first to create all of the various wonders that mark the track of human progress, does indeed illustrate the ancient concerns about the dangerous caprices of the planet. But seemingly it didn't do very much. If it worked at all, it might have let the emperor know that there had been a distant vibration in his realms; and since the dragons were arranged around the points of the compass, it might also have allowed him to learn more or less in which quarter of his domains this vibration had occurred. It is said that this happened once: The ball dropped and the emperor was able to say that there had been a quake in Hunan Province—and lo, a few hours later a messenger arrived with the news that there had indeed been an earthquake in Hunan.

Joseph Needham, the great Cambridge scholar of Chinese scientific history, was one of the first to present pictures of how Zhang Heng's second-century “earthquake weathercock” might have looked. He contends that the instrument was improved and used by subsequent court astronomers in China until at least the eighth century, with the basic idea finding its way to the West by way of Persia.

The device was beautiful, clever, and prescient—but probably so inaccurate as never to have enjoyed more than the most symbolic use. And, like so much that was created in early China, it was neither advanced nor improved upon, at least not by the Chinese.

It took Western science to do that—although it happened that in
this particular case it was Western science that was by chance operating in the East. Crude vibration detectors were built in the eighteenth century, but the first modern device worthy of being called a seismograph—an instrument that is able to detect the earth's movements with precision and, unlike the frog-and-dragon-balls affair, to make a record of it at the same time—was invented in 1896 by a Yorkshire wool-dealer's son named John Milne. He invented it while he was studying the earthquakes that occurred with troubling frequency not in Yorkshire but in Japan.

His basic idea has remained the guiding principle behind the instrument ever since, and in essence it is the one that guided Zhang Heng's instrument of sixteen centuries before: A pendulum with a pen is allowed to swing against a paper-covered and clockwork-run recording drum fixed solidly into a case bolted securely to the ground. Any shaking generated by an earthquake will cause the drum and the pendulum to move relative to each other, and the movement will be written by the pen onto the unrolling sheet of paper. (The terminology is more or less self-explanatory; the recording instrument is, strictly speaking, a
seismometer
; the entire package of instruments is a
seismograph
; the record to be studied later is a
seismogram
.)

John Milne constructed his brass, steel, and wire machine while serving as professor of geology at the Imperial College of Engineering in Tokyo, after he found himself frustrated by the inaccurate and shoddily made instruments that were put at his disposal to study the Great Yokohama Earthquake of 1880. And, while his device (sometimes called a Milne Seismograph but equally often called a Ewing, after his colleague-inventor James Ewing) was very accurate and as handsome as most Victorian scientific devices (it was manufactured by the famous, and still existing, instrument-making firm of R. W. Munro), it was soon to be supplanted by scores of instruments with much more exotic European and Asian names.
*
These would in due course become electronic and digital and accurate to unimaginable degrees.

In 1906 there were ninety-six seismographs in existence in the world, many of them Milnes or Ewings. So great was the shock emanating from San Francisco that practically every single one recorded it. Some were nearby—those in San Jose, Berkeley, and Yountville, California, and Carson City, Nevada, were so close to the event that their needles and drums recorded the destruction of buildings just yards away. At Stanford there was a Bristol's Recording Voltmeter: an instrument designed to measure an altogether different kind of phenomenon, but that, since it had a needle, a pen, and a sheet of clockwork-driven paper, also noted the vibration with a spectacular set of indelible black-ink flailings.

Most of the true seismographs, though, were a good deal farther away: There were seismographs of all kinds in an almost alphabetically complete list of places that includes Apia, Bombay, Cairo, Dorpat, Edinburgh, Florence, Honolulu, Irkutsk, Jena, Kew, Leipzig, Mauritius, Osaka, Perth, Quarto-Castello, Rio, Sitka, Tiflis, Uppsala, Vienna, Wellington, the aforesaid Yountville and Zagreb, and, making up for the alphabetical absences of towns beginning with
g
,
n
, and
x
, an additional
z
, the small Chinese city that was possessed of a borrowed Japanese Omori machine, a half-forgotten place then known as Zikawei.

Only half forgotten, however. Zikawei used to be a small town southwest of Shanghai: It is now thoroughly subsumed into its neighbor, bears the name of Xujiahui, and is as filled with skyscrapers, nightclubs, and subway lines as any other part of the world's fastest-growing city. A century ago this village was a place of colleges, orphanages, and hospitals—and, most interesting for this story, it also had a
large Jesuit mission. The Omori seismograph that recorded the San Francisco Earthquake had been loaned specifically to the Jesuit Observatory of Zikawei—a happenstance that serves to underline the generally forgotten fact that the Jesuits and seismology have enjoyed a long and intimate connection, and that no small number of the machines scribbling down the record of the Californian events of that April morning were in fact maintained and operated by monks and priests ordained in the Society of Jesus.

The society, right from its sixteenth-century beginnings, was predicated on the basis of promoting scholarship and learning, particularly in the fields of mathematics, astronomy, and what were once called the natural sciences. By the seventeenth and eighteenth centuries most Jesuit colleges had departments that studied the earth and the stars; and in China, where the society had long had a foothold, the Manchu court appointed Jesuits to direct the Peking Astronomical Observatory.

The patient, monastic observers who maintained these schools soon noticed the terrible disruptions caused by earthquakes—and once the precursor to the machine that was eventually to be called the seismograph
*
had been invented in the 1750s, the society's leadership decided, as a matter of canonical policy, that in those areas where earthquakes were common it would be the Jesuits' holy duty to investigate them and, by doing so, perhaps help to mitigate the misery that such unpredictable events brought to God's people.

So the first Jesuit seismograph—a crude two-pendulum arrangement of a type that would these days be somewhat dismissively called a seismoscope, since it never left a written record—was installed at the Manila Observatory in 1868. The next was installed the following year in a monastery in Frascati, Italy. Then one was built in Granada, Spain, another at Mungret College, County Limerick, another at Stonyhurst College in Lancashire, another on the island of Jersey, the first American instrument in 1900 in a Jesuit college in Cleveland, Ohio. And finally, in 1904, the Omori seismograph from Japan was carefully assembled in a special observatory building at the mission college in Zikawei.

This was the device that registered the San Francisco shock waves—one of four maintained by Jesuits around the world at the time. It was responsible for detecting the impressive set of shocks from which the earthquake's approximate epicenter was determined. (The Shanghai instrument was replaced in 1932 by a newfangled contraption winningly known as a Galitzin-Wilip instrument, and it operated outside the great city until 1949, when the Chinese Communists turfed the Jesuits out.)

The installation of Jesuit seismographs accelerated rapidly after the disaster of San Francisco (with one instrument being installed in Addis Ababa as late as 1957), and for much of the twentieth century in America the Jesuits wielded a considerable influence over the entire seismological community, helping to direct the research that has shaped much modern thinking about the planet's mysterious convulsions. And to this day four large Jesuit institutions—in St. Louis, Bogotá, La Paz, and Manila—continue to observe and conduct research into plate tectonics, keeping the scientific tradition of this unique form of Catholic inquiry very much alive. Most of the small observatories have closed down (though the one at Stonyhurst College still functions, courtesy of the schoolchildren themselves), and the Zikawei machine is, of course, thanks to Maoist suspicions, no more. But their records—the etched traces on smoked-paper drums, the wavy lines of ink on now-yellow graph paper, and, the least scientifically satisfying but the most spectacular of all, ink traces made by a pendulum waving this way and that over a fixed circle of paper—remain.

What was recorded in all of these observatories, Jesuit owned or not, depended on the sophistication of each seismograph. The simple pendulums—like that in the Chabot Observatory in Oakland, just across San Francisco Bay—produced not much more than ragged messes of ink, most of them “too confused to give details.” Lawson's report for Oakland presents raw data typical of these primitive instruments: The machine allowed investigators to say little more than that “the movement of the pendulum … was in nearly all directions, and more or less irregular, tho' this irregularity was undoubtedly in part due to the pendulum's striking against the side of the case.”

But better instruments followed—some in America, some in the Jesuit monasteries, many in Europe. Some of the best were the Bosch-Omori machines in Washington, D.C., at the New York State capital of Albany, and at the U.S. Navy base in Vieques in Puerto Rico. Each of these left a long trace of ink on a time-marked paper roll, and, by poring over the traces later, investigators were able to determine when the first tiny tremors started to be detected; when the secondary set of preliminary tremors began to rattle the needle; when the regular shear waves and pressure waves started to arrive—with the time difference between the two types, as we have seen, enabling the instrument readers to work out how far away the earthquake's originating point was; then when the principal part of the tremor was under way; and finally when the maximum disturbance occurred.