Earthquake Storms

by John Dvorak

  The institute’s president asked the soon-to-be graduate whether he might be interested in staying at the institute and working in a different field. A seismological laboratory had recently been organized and earthquake records were accumulating at a fast pace. Would Richter be willing to examine and catalogue those records?

  The 23-year-old did not hesitate: Yes, indeed, he was interested. And so a crucial element in the history of seismology was born.

  The first sismografo, or seismograph, an instrument that could record on paper the seemingly erratic motions of the ground during an earthquake, was built in the 1850s by Luigi Palmieri, then the director of Vesuvius Observatory in Italy. His design was something of a Rube Goldberg affair—it consisted of a series of complex gadgets including two U-shaped glass tubes containing mercury, a pair of electromagnets, a few coiled springs, a host of levers, a pen and a roll of paper, and a pair of pendulum clocks that worked in sequence—an instrument complicated by today’s standards, but one that did produce some of the first permanent records of earthquake shaking. To set up Palmieri’s sismografo was also complicated. Each element had to be carefully adjusted to move whenever the ground started to vibrate, even feebly.

  To prepare it to record an earthquake, one clock was set to the correct time and its pendulum set to swing, while the other clock and its pendulum were stationary. Then when the ground shook, the level of mercury in each glass tube changed. That change completed an electric circuit that sent power to the electromagnets that caused sequences of levers to move. One sequence stopped the pendulum of the running clock, thereby establishing the time of the earthquake. Another sequence of shifting levers started the pendulum of the second clock to swing, the swinging of the pendulum continuing until the ground shaking stopped. That caused the mercury to return to its original level, which opened the electric circuits, which cut off the power to the electromagnets, which caused the levers to move back, which stopped the swing of the second pendulum, thus allowing someone to read, from the second clock, the duration of the earthquake.

  The second clock also had another purpose: As soon as the pendulum started to swing, a spring was released that unraveled a roll of paper. And as the paper unraveled, it ran under a pen that etched a permanent trace of the ground shaking.

  In all, it was a hopelessly complicated instrument that needed constant adjustment and frequent repairs, though Palmieri claimed that, on April 23, 1872, his sismografo “became agitated,” and a day later lava gushed from the main crater and reached the foot of Vesuvius in a couple of hours. It was a clear forewarning of an eruption by recording earthquakes, but Palmieri’s instrument was never used widely and has no modern descendants.

  The direct ancestors of today’s seismographs—properly called “seismometers” because the emphasis has been on devising a means to “meter,” or measure, ground motion—are a series of instruments designed and built by John Milne, a British mining engineer who in 1876 arrived in Japan to teach at the Imperial College of Engineering in Tokyo. On the night of his arrival in Japan, he felt his first earthquake ever. From that, he became fascinated by seismic shaking and how it might be recorded and what could be learned from it.

  Milne’s instruments relied on the same basic principle: the movement of a horizontal pendulum. In his most popular and successful instrument, he placed one end of a rigid horizontal bar against a vertical post, leaving the other end free to swing, similar to how a door swings on its hinges. When an earthquake hit and the ground shook, the horizontal rod swung back and forth, causing a pen attached to the free end to trace out a record of the ground motion on a piece of paper attached to a slowly revolving drum.

  A Milne-type instrument was the first type of seismometer to operate in the United States, installed at Lick Observatory in California in 1887. The first earthquake it recorded was a “slight shock” on April 24, 1887. The time of the earthquake was given in the logbook at Lick as “night.”

  By the 1910s, Milne-type seismometers were in use at more than 100 sites around the world. Most were in Japan and Europe. Instruments were also being used in Shanghai, China, in Havana, Cuba, and Manila in the Philippines. Others were operating in Sitka, Alaska, and in the Canal Zone in Panama. Colleges in the United States had them installed in Albany, New York; in Baltimore, Maryland; in Cambridge, Massachusetts; and of course in Berkeley, California. Several were maintained by the Carnegie Institution in Washington, D.C. And one was in operation at the top of a volcano in the Hawaiian Islands. But all of these instruments had major drawbacks: They were expensive and heavy—a single instrument cost about $1,000 and weighed a few hundred pounds—and because of the design they could only record relatively slow oscillations, and therefore could only be used to study seismic waves that arrived from distant earthquakes. In order to record the rapid oscillations of local earthquakes, and thereby be able to locate them accurately, a new design was needed.

  One was successfully developed at Millikan’s California Institute of Technology and was operating by 1921. Known as the Wood-Anderson seismometer, it was named for its two inventors, Harry Oscar Wood and John Anderson. Wood had worked for Lawson after the 1906 earthquake, producing a map of shaking intensity based on the severity of damage found throughout the Bay Area. In the 1920s, supported by the Carnegie Institution, he founded and was the first director of the Seismological Laboratory, located in Pasadena. Anderson was a designer and builder of astronomical equipment for the new telescopes then being constructed at Mount Wilson north of Pasadena. Together, they produced an instrument that was small, lightweight, and inexpensive to build—and that could record local earthquakes.

  Their design was still based on a horizontal pendulum, though of very small size. A thin wire of tungsten was stretched tightly between the ends of a narrow metal cylinder. Attached to the wire was a small ball of copper. When the ground shook, the cylinder vibrated, causing the ball of copper inside the cylinder to twist back and forth on the wire.

  It was a remarkable feat of engineering, foremost because even a tiny amount of shaking would cause the copper ball to twist the wire ever so slightly.* A Milne-type instrument could magnify ground motion about 100 times. A Wood-Anderson instrument, because it was lightweight and delicate (the ball of copper weighed only three-hundredths of an ounce, about one gram), could magnify ground motion more than 2,000 times! And the motion was recorded on a roll of paper, similar to the Milne-type instruments.

  When Richter began working at the Seismological Laboratory in 1927, four Wood-Anderson seismometers were in operation in southern California—one in Pasadena, another in Riverside, and two along the coast at La Jolla near San Diego and at Santa Barbara. Richter’s job was to examine a day’s record from each station, noting when the first disturbance of an earthquake had arrived at each station, as well as any other notable characteristics of the seismic waves. He got so good at recognizing wave trains that once, late in life, inspecting a record, he could tell a colleague, “This seems to be exactly the same seismogram as one I saw five years ago.”

  The arrival times for each earthquake were then used to compute where the earthquake had originated. Richter also wanted to give some indicator of the size of an earthquake, initially planning to list it as “small, intermediate, or large.” But he abandoned that idea when in 1933 an earthquake struck south of Los Angeles at Long Beach and there was the mistaken impression by the public, because many buildings had been damaged and some fatalities had occurred, that this had been “a great earthquake,” comparable to the 1906 event.

  Richter, examining the tracings from the seismometers, knew different. But how could he convey this in a simple manner to the public, who had witnessed such visible signs of physical destruction?

  The Long Beach earthquake struck on Friday, March 10, 1933, at five minutes to six in the late afternoon. Richter was still in his office, planning to attend a meeting of a local chess club later that night.

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p; He happened to be looking in the direction of one of the revolving drums where an ink pen was tracing out the signal from one of the seismometers and noticed that the pen started to move just as the seismic wave hit the building. As he would recall, he made “appropriate remarks”—one assumes these were directed at the shaking and contained expletives—then moved closer to the drum.

  The pen was now swinging wildly. All that told him was that a powerful earthquake had struck somewhere near Los Angeles. Then the telephones started to ring.

  By talking to callers, Richter could determine that the earthquake was centered somewhere south of Los Angeles, a conclusion borne out by later radio newscasts. In fact, the greatest damage was at Long Beach, where practically every building in the business district was left in shambles. Here and in nearby communities, more than 100 people were killed.

  Notwithstanding the extensive damage and the death toll—the earthquake had originated almost directly beneath Long Beach—from a seismic perspective this had been a moderate earthquake, not a major one. And the idea, quickly voiced in newspaper editorials, that the people of southern California could now relax because no more important shocks need be expected for many years was a false one. As Richter would later write in his textbook Elementary Seismology, “A small shock perceptible in the Los Angeles metropolitan center will set the telephone at the Pasadena laboratory ringing steadily for half a day, while a major earthquake under some remote ocean passes unnoticed except for seismograph readings and rates a line or two at the bottom of a newspaper page.”

  How to change that perception? For the past year or so, Richter had been working on an idea, first proposed by Kiyoo Wadati in Japan, to use the maximum ground displacement during an earthquake as a measure of its size. But there was a lot of variation here: Earthquakes occurred at different distances from seismometers, the ground responded differently depending on the nature of the surface—loose sediments shook significantly more than solid rock—to name just two, and a strong earthquake in an unpopulated region would be reacted to differently in the hearts and minds of the public than a much weaker one that occurred in a large populous city.

  Richter at least had a way to account for the physical variations: He had access to the densest network of seismometers and to the largest number of seismic records in the world. And earthquakes were being recorded at a rate of about 100 events per year on the network of Wood-Anderson seismometers. So he had an abundance of data to study.

  And, just as important, he reveled in hunching over a table with a pencil, a ruler, and a pad of paper, measuring his seismograms. People often found him working alone in the measuring room, talking to himself. In fact, he seemed capable of carrying on long conversations with himself.

  He also loved to calculate. Numbers clearly soothed him. Among his professional papers, kept at the archives at the California Institute of Technology, is a box filled with his search for prime numbers, which is a number that is divisible only by itself and by the number one.

  But his mood was unpredictable; it was not possible to judge what might inflame him. On one occasion, recounted in Hough’s Richter’s Scale, he stormed out of a meeting and slammed a door behind him, shattering the glass pane. After a few seconds of dead silence in the room, Richter returned and informed his colleagues, “I am not sorry about what I said but I am sorry about the door.”

  Nevertheless, during those long, solitary days he found a way to determine the size of earthquakes, and from that he was able to propose his famous earthquake magnitude scale.

  There are many misconceptions about Richter’s magnitude scale. First, it is not a physical device. There is no specially inscribed ruler or other measuring instrument. As Richter often stressed, it is a method, and so it was not invented but devised.

  Second, the magnitude scale is arbitrary—that is, it does not have any physical meaning. In this regard, the magnitude scale is similar to the much more familiar Fahrenheit (or Celsius) temperature scale, which is also arbitrary. Both the Fahrenheit temperature scale and Richter’s earthquake magnitude scale are based on a specific way to measure temperature and ground displacement, respectively. The Fahrenheit scale, developed in 1724 by Daniel Gabriel Fahrenheit, relied on the use of a mercury thermometer; the earthquake scale, as noted, relied on a Wood-Anderson seismometer.

  Both also have arbitrary zero points. For the temperature scale, 0°F was the lowest temperature Daniel Fahrenheit could achieve by preparing a mixture of water and salts. For the earthquake scale, Richter decided that an earthquake of magnitude zero would correspond to the smallest displacement a Wood-Anderson seismometer could measure—0.00004 inch, or one micron, about one-hundredth the diameter of a human hair, if the seismometer was 62 miles, or 100 kilometers, from the earthquake.

  As to establishing the interval size of each scale, for the temperature scale, Daniel Fahrenheit, for a reason still debated by science historians, said the boiling point of mercury was 600°F, probably to make the temperature of the human body—98.6°F—close to 100. As to the earthquake scale, Richter realized by inspecting his seismograms that ground displacements during earthquakes could range by more than 1,000,000, and so the earthquake scale became a logarithmic scale. That simply means that, for every increase of ground displacement by a factor of ten, the earthquake magnitude increases by one unit. This is easiest to understand with an example.

  If the maximum displacement produced by an earthquake at a distance of 62 miles, or 100 kilometers, is one micron, then, as already noted, the Richter magnitude is zero. If the maximum displacement at the same distance is 10 microns, then the magnitude is one; if the maximum displacement is one millimeter—about one-twentieth of an inch—the magnitude is three; and so forth.

  According to this scale, if the maximum ground displacement at a distance of 100 kilometers is 100 millimeters—about four inches—then a magnitude-5 earthquake has occurred—and, from experience, many people may have felt the earthquake and there may be some damage.

  It is important to note that there is no upper bound to an earthquake magnitude: A magnitude-10 earthquake is possible, but it does not happen because of the material the Earth is made of and because of the planet’s size; it is, as Richter often said, “a limitation of the earth, not in the scale.”

  Richter formally announced his earthquake scale in 1935. It took a few years for the seismological community to adopt it, but it remained essentially unknown to the public until 1952 when the first strong earthquake since his development of the scale struck California. It occurred in an agricultural district south of Bakersfield in Kern County along the White Wolf Fault. This earthquake was strong enough to shorten a railroad tunnel by three feet, leaving the rails bent into S-shaped curves. A study of his seismograms and some calculations showed that it was a magnitude-7.5 event. Because of its location, it did little damage—a few broken windows and cracked plaster, though 12 deaths occurred when a building collapsed. By comparison, the 1933 Long Beach earthquake was a magnitude-6.3 event and, because it occurred in a highly populated area, it devastated several communities and killed more than 100 people.

  Since 1952, Richter magnitude has been a staple of earthquake reporting. Moreover, the phrase “off the Richter scale” has come to mean that something is too extreme to measure or so awesome that it is unbelievable. Political commentators use the expression to indicate when an election campaign is in calamity. It also appears in slang, as in “Dude, we were boardin’ yesterday and the waves were off the Richter scale!”

  The calmest period in Richter’s life, when he seemed free of nervousness and other anxieties, was the years he spent devising his magnitude scale. It was at the end of this period—when he introduced his scale—that he and his wife of seven years, Lillian, began to join nudist colonies.

  Lillian and Charles had married in 1928; he later mentioned to friends that she was “a little wild” at the time. The nature of her “wildnes
s” he never explained, though at the time she met Richter Lillian was married, had a son, and was separated from her husband. Her attraction to nudism she never explained.

  His attraction is clear. One might expect that, because as a youth he had gone on numerous day hikes to the nearby San Gabriel Mountains and on overnight trips to the southern Sierra Nevada Mountains, his attraction to nudism came about as an extension of his outdoor activities. But it was not. It was about friendship.

  “I might say,” Richter would write, “that I have never known what real friendship was; I have never had any intimate friends—until we joined the Glassey group.”

  The Glassey group referred to psychotherapist Hobart Glassey and his wife Lura, who ran the Fraternity Elysia, a nudist organization located in a small canyon along La Tuna Canyon Road mid-way between Pasadena and the San Fernando Valley. It was one of the first nudist camps in the United States, opening in 1934. Here Richter was no longer a professor, nor was he known as Charles; instead, he was called “Charlie.” It is unknown whether he shared with other members of the group anything about his professional life. Whatever it was about this nudist colony, for “Charlie” social barriers and anxieties came crashing down along with clothing, allowing him to connect socially in a way he never could before, even amongst his scientific colleagues. Nor is it known how long he and Lillian remained members—the Fraternity Elysia closed in 1946—though in later years, according to family members, Richter and his wife apparently continued to practice nudism on their own during backcountry hikes.