[12. One of the uses of GPS is to measure these bulges as markers of accumulating strain. But old-fashioned methods also work. In Indonesia, it had long been known that the shallow near-shore waters (which are part of the island's plate, not the seabed's) were rising. This was evident from the fact that coral reefs had been steadily pushed above sea level, killing the coral. By determining the date at which each stratum of coral died, it was possible to chart the rate of uplift. Ironically, in early December 2004, less than three weeks before Boxing Day, a group of geophysicists unveiled a brochure they had been preparing for distribution in Indonesia, explaining what this meant and outlining the earthquake risk.]
In the big picture of plate tectonics, all sections of a plate are trying to move in the same direction.[13] But slippage isn't always uniform along the rupture zone. In part, that's why big temblors generate aftershocks, as various portions of the rupture zone settle into new equilibrium. On Boxing Day alone, there were 142 aftershocks of magnitude 5.0 or larger.
[13. In Indonesia, the Indian Ocean's plate is moving northward.]
Then, a month later (on January 27), forty-eight such shocks occurred in rapid-fire succession, midway along the Boxing Day rupture zone. Meredith Nettles of Harvard University has dubbed these the Nicobar Island cluster because they occurred near an island of that name.
Nothing like them had ever been seen before. They look like aftershocks from a temblor of magnitude 8.0 or larger, but there was no main temblor. Also, all of the Nicobar shocks were confined to a 25-kilometer circle.
Briefly, seismologists thought they might be precursors to a large volcanic eruption, but that didn't happen, either. Nettles’ belief is that the cluster represents a segment of the top plate releasing strain from the non-uniform motion of the Boxing Day event—and somehow doing so without ever unleashing a big quake. To seismologists, this non-event was extremely exciting; to nearby residents, of course, it was blissfully unexciting.
Unfortunately, other parts of Indonesia may not be so fortunate.
Indonesia's offshore fault zone appears to have three segments: north, central, and south. The northern segment was the one that produced the Boxing Day quake (and the Nicobar Island cluster). Portions of it had ruptured in 1847, 1881, and 1941, producing events of approximately magnitude 8.0.
The other two segments both ruptured during the Nineteenth Century: the middle one in 1861 (magnitude somewhere between 8.3 and 8.5) and the southern in 1833 (magnitude 8.8-9.2).
The March 28 quake ruptured the middle segment along almost exactly the same boundaries as the 1861 event. To date, the southern segment has been quiescent, but worried scientists are scrambling to deploy instruments, because this segment lies offshore from some of Indonesia's most densely populated areas, including Jakarta.
The issue is whether the three segments move separately, or are more like dominoes, with movement in one shifting strain to the next in line. Hints to the answer can be found in maps of the Indian Ocean seabed. These show parallel ridges running north/south, in the direction of the plate's movement, more or less at the boundaries of the three segments.
The ridges represent places where lava oozed up along cracks in the seabed. The question, says Oxford University geophysicist David Robinson, is what that means. One possibility is that the ridges reflect weaknesses that divide the seabed into mini-platelets that move more or less independently. The other is that the ridges are sticky spots that increase the friction of the seabed plate as it slides into the subduction zone. If so, they might temporarily block a rupture in one zone from proceeding to the next. But if the two sides of the ridge are still firmly connected, slippage on one side has greatly increased strain on the other, making it likely that it will soon follow suit. There's only one way to find out which theory is correct, and that's by dumping a lot of money into understanding Indonesia's plate tectonics.
If nothing else, the Boxing Day quake proved that nature can still take us by surprise. “One casualty, if I may use that word, is our sense of large-scale plate tectonics,” says Okal. “We thought we understood subduction zones based on the age of the plate and the speed of convergence. But Sumatra sends us back to the drawing board. Very few people were willing to bet that this region could entertain a major thrust, and it did. Perhaps all of these regions are capable of violating the canons of our previous understanding."
As long as such uncertainties persist, the long-run future will probably involve total global monitoring. Already, scientists can access a great many seismometer readings, online. As instruments become ever less expensive and data transmission capabilities become ever-greater, it's easy to envision a world in which seismometers, GPS sensors, hydrophones, and infrasound detectors are all wired into an interconnected earthquake-alert system. And while today's satellites are too few to monitor tsunamis except by the luck of being in the right place at the right time, it's easy to imagine a future in which far more sophisticated satellites monitor the entire globe from geostationary orbit.
* * * *
Automated Shutdowns
So far, we've focused mostly on how to warn for tsunamis. But earthquakes also knock down buildings and kill people directly, even if they're miles from the ocean. Is there any way to provide advance warnings of this?
Surprisingly, the answer is “yes.” In fact, such warning systems already exist: not in the U.S., but in Taiwan, Japan, and Mexico.
The trick is to remember that however quickly seismic waves travel, electronics are faster. That means that if you install enough seismic stations, there's a reasonable chance that at least one will lie close to the epicenter—providing time, if you act quickly, to tell people what's headed their way.
Taiwan's warning system takes advantage of the fact that most of that nation's earthquakes occur in the southern part of the island, whereas most of the people live in the north. Since earthquake shock waves travel at about 100 miles per minute, a big temblor in the south will start triggering seismic stations there as much as a minute before it hits the north. Similarly, Mexico City gets about seventy seconds’ notice when quakes occur on the Pacific coast.
It's even possible to develop a system that gives warning of earthquakes going on practically beneath you, though for a system like that to be useful, it has to be ultra-rapid. To do this, Richard Allen, a geophysics professor at the University of Wisconsin, has developed a computer program called ElarmS, which takes advantage of the fact that earthquakes produce two types of shock waves, called P-waves and S-waves. P-waves are pressure waves that vibrate in the direction in which they are traveling. They travel quickly, but carry less energy than the S-waves (or shear waves), which vibrate sideways.[14]
[14. For years, seismologists have used the time lag between the arrival of P-waves and S-waves to determine the distance from a seismometer to an earthquake.]
Allen's brainstorm was to use the P-waves to predict the strength of the approaching S-waves. In a 2002 study published in Science, he demonstrated that this could be done within one second of the arrival of the first P-wave. Obviously, such a program won't give a good estimate of magnitude, especially for mega-quakes such as the Boxing Day temblor. But it should do a decent job of sorting out damaging earthquakes from minor tremors.
Such a warning system requires a great many seismometers, because its first hint of the earthquake's location comes from knowing which seismometer is hit first. As additional instruments begin to register the temblor, it's possible to triangulate, but if they're too widely scattered, it's already too late.[15]
[15. One of the few places on the globe with enough stations to make such a system work is Southern California, were a $20 million federal grant was used to create a 155-station network called TriNet.]
Once an earthquake is sensed, the next step is to generate what the U.S. Geological Survey calls a “ShakeMap,” which shows the degree to which surrounding areas are likely to be affected. Allen estimates that ShakeMaps could be created (and updated) in ab
out four seconds.[16]
[16. Obviously, you also need to know the region's geology, to predict how the shaking will affect various areas. In places like California, this is well known, but geological mapping of all of the world's earthquake zones is another good project for the]
What can be done with less than a minute's warning? Well, that's plenty of time for residents to get out of dangerously constructed buildings. Hospitals can lock down wheels on gurneys and beds. Schools might have time to evacuate classrooms. In Taiwan, bullet trains automatically apply the brakes when a warning is issued, and emergency crews are dispatched to places where they are most likely to be needed. Additional options, Allen says, would include automated shutdowns of industrial processes, aborting airplane landings, and closing bridge and freeway entrances. Even a ten-second warning might give people time to take cover, or to move away from dangerous machinery or chemicals. For a doctor engaged in delicate surgery, even five seconds’ notice might be enough to stave off disaster.
The future may bring buildings designed to make use of such warnings via “active” earthquake protection devices that are turned on by the alarm. Such devices, already in use in Japan, shake the building in a manner that offsets the swaying imparted by the earthquake. One system employs a giant piston mounted horizontally on the top floor. When an earthquake hits, the piston begins to pump in counterpoint to the seismic vibrations, neutralizing the building's sway.
Normally, such devices are linked to motion sensors in the building itself, but that raises the prospect of a false alarm setting off the piston, damaging the building even though there is no earthquake. An advance warning system could be used to confirm that a vibration is real, and not simply the result of a janitor banging a cart into one of the building's internal sensors.[17]
[17. I am indebted for this information to Andrew Smyth, a civil engineering professor at Columbia University, who described it in December 2003, on a tour of San Francisco's earthquake-prevention efforts, at a meeting of the American Geophysical Union.]
Some people are concerned, though, that however useful earthquake warnings might be for automatic shutdowns, they might produce widespread panic.
Not so, said James Goltz, of (California's) Governor's Office of Emergency Services in a 2003 press conference. Social science research has found that instead of panicking in the face of warnings, people tend to suffer from the illusion that nothing is actually amiss. “The sun is still shining,” Goltz said. “The birds are still singing. There's no indication that strong ground motions are hurtling toward them."
More troublesome is the fact that many people will be leery of automated warnings and will want the data to be evaluated by a human decision-maker before a warning is issued. “Given the very short time frame,” Goltz said, “that's not a good idea."
Copyright © 2006 Richard A. Lovett
* * * *
About the Author: Richard A. Lovett lives in Oregon, where he has the distinction of being science fiction's only Red Lizard. What exactly these ruddy reptiles are, he won't say, other than that they dash to the top of a 1,000-foot hill called the “Goose” every Thursday evening. A hint to the group's purpose may lie in the fact that Richard has coauthored two running books with former marathon record-holder Alberto Salazar. Between sprints, he writes for such publications as New Scientist, Psychology Today, Running Times, and National Geographic News, and tries to write at least a bit of fiction every week.
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* * *
TAKES TWO TO TANGLE
by Ben Bova
Research, by the nature of the beast, tends to lead to surprises....
One Sam Gunn is bad enough. But now there are at least two of them, maybe more, and it's all my fault.
Well, mostly my fault. Sam had something to do with it, of course. More than a little, as you might suspect if you know anything about Sam.
And, if you know anything about Sam, you know that of course there was a woman involved. A beautiful, statuesque, golden-haired Bishop of the New Lunar Church, no less.
I didn't know anything about Sam except the usual stuff that the general public knew: Sam Gunn was a freewheeling space entrepreneur, a little stubby loudmouthed redheaded guy who always found himself battling the big boys of huge interplanetary corporations and labyrinthine government bureaucracies. Sam was widely known as a womanizer, a wise ass, a stubby Tasmanian Devil with a mind as sharp as a laser beam and a heart as big as a spiral galaxy.
He had disappeared a couple of years earlier out on some wild-ass trek to the Kuiper Belt. Everybody thought he had died out in that frozen darkness beyond Pluto. There was rejoicing in the paneled chambers of corporate and government power, tears shed among Sam's legion of friends.
And then after his long absence he showed up again, spinning a wild tale about having fallen into a black hole. He was heading back to Earth, coming in from the cold, claiming that friendly aliens on the other side of the black hole had showed him how to get back to our spacetime, back to home. Sam's enemies nodded knowingly: of course the aliens would want to get rid of him, they said to each other.
And they sent just about every lawyer on Earth after Sam. He owed megabucks to dozens of creditors, including some pretty shady characters. He was so deeply in debt that there was no place on Earth he could land his spacecraft without having umpteen dozen eager lawyers slam him with liens and lawsuits.
Which is why Sam landed not on Earth, but on the Moon. At Selene, which was now an independent nation and apparently the only human community in the solar system that didn't have Sam at the head of its “most wanted” list.
He came straight to the underground halls of Selene University. To my office!
Imagine my surprise when Sam Gunn showed up at my doorway, all one hundred sixty-some centimeters of him.
And asked me to invent a matter transmitter for him.
“A matter transmitter?” I must have sputtered, I was so shocked. “But that's nonsense. It's kiddy fantasy. It's nothing but—"
“It's physics,” Sam said. “And you're a physicist. Right?"
He had me there.
I am Daniel C. Townes IV, PhD. I am a particle physicist. I was on the short list last year for the Nobel Prize in physics. But that was before I met Sam Gunn.
Sam had popped into my office unannounced, sneaking past the department secretary during her lunch break. (Which, I must confess, often takes a couple of hours.) He just waltzed through my open doorway, walked up to my desk, stuck out his hand and introduced himself. Then he told me he needed a matter transmitter. Right away.
I sagged back in my desk chair while Sam perched himself on the only bare corner of my desk, grinning like a gap-toothed Jack-O-Lantern. His face was round, with a snub nose and a sprinkling of freckles. His eyes were light, twinkling.
“Physics is one thing,” I said, trying to regain my dignity. “A matter transmitter is something else."
“Come on,” Sam said, wheedling, “you guys have transmitted photons, haven't you? You yourself just published a paper about transmitting atomic particles from one end of your lab to the other."
He had read the literature. That impressed me.
You have to understand that I was comparatively young at the time. Young enough to think that I might be the youngest person ever to receive the physics Nobel. I had to be careful, though. More than one young genius had been cut down by the knives that whirl through academia's hallowed halls in the dark of night.
I think Sam had roosted on my desk because that made him taller than I was, as long as I remained sitting in my swivel chair. I have to confess, though, that there wasn't anyplace else he could have sat. My office was littered with reports, journals, books, even popular magazines. The visitor's chair was piled high with memos that the secretary had printed out from the department's unending file of meaningless trivia. There might be no paper on the Moon, but we sure do pile up the monofilament plastic sheets that we use in its place.<
br />
“So how about it, Dan-o?” Sam asked. “Can you make me a matter transmitter? It's worth a considerable fortune and I'll cut you in on it, fifty-fifty."
“What makes you think—"
“You're the expert on entanglement, aren't you?"
I was impressed even more. Entanglement is not a subject your average businessman either knows or cares about.
Curiosity is a funny thing. It not only kills cats, it makes physicists forget Newton's Third Law, the one about action and reaction.
I heard myself ask him, “Did you really survive going through a black hole?"
Grinning even wider, Sam nodded. “Yep. Twice."
“What's it like? What did you experience? How did it feel?"
Sam shrugged. “Nothing to it, really. I didn't see or feel anything all that unusual."
“That's impossible."
Sam just sat there on the corner of my desk, grinning knowingly.
“Unless,” I mused, “the laws of physics change under the intense gravitational field..."
“Or I'm telling you a big, fat lie,” Sam said.
“A lie?” That stunned me. “You wouldn't—"
“Look,” Sam said, bending closer toward me, “I need a matter transmitter. You whip one up for me and I'll give you all the data in my ship's computer."
I could feel my eyes go wide. “Your ship? The one that went through the black hole?"
“Twice,” said Sam.
Thus began my partnership with Sam Gunn.
* * * *
Ingrid MacTavish was something else. A missionary from the New Morality back Earthside, she had come to Selene to be installed as a Bishop in the New Lunar Church. She was nearly two meters tall, with bright golden hair that glowed and cascaded down past her shoulders, and eyes the color of green tourmaline. A Junoesque goddess. A Valkyrie in a virginal white pants suit that fit her snugly enough to send my blood pressure soaring.
Analog SFF, October 2006 Page 10