YOU never really get used to earthquakes.
- You wishes the warning would come minutes, rather than mere seconds, earlier. And nowadays there is no technical reason why it should not. Thanks to low-orbit surveillance and communications satellites, such alarm systems are being used along the eastern edge of the Indian Ocean to warn coastal communities of imminent tsunamis.
- In Japan, they tell speeding bullet-trains to slow down in time to prevent derailments. One day, such earthquake early-warning systems could be as ubiquitous in the home as smoke detectors—at least, in seismically active areas.
- Providing five-minute warnings of earthquakes is one thing; predicting them days or weeks ahead is quite another. Detecting the primary waves from an earthquake is like seeing the flash of lightning before hearing the thunder and getting drenched by the rain. It is an integral part of a deterministic process that is already under way.
- The magnitude and timing of an earthquake depend on the size of the fault being ruptured, the stiffness of the rocks in question and the amount of stress that has accumulated in them. Scientists can make rough guesses of what they may be, but the deterministic devil is in the details. Understanding what is happening—at the level of detail that determines the actual outcome—is impossible.
- That has not stopped people trying. Pseudo-scientific theories and predictions about earthquakes abound. Over the centuries, people have tried everything from the behaviour of animals and unusual cloud formations to the water level in wells and the phases of the moon to predict earthquakes.
- More recently, researchers have sought to associate electromagnetic fields, the radon or hydrogen content of the soil and seismicity patterns with impending earthquakes. All to no avail.
- So far it has proved impossible to predict earthquakes in any meaningful way—that is, of a given magnitude, at a given place, on a given day. That is because of the complexity of the problem and the lack of information about how the stresses around the cat’s cradle of neighbouring faults accumulate in some places and are relieved in others. Anyone who says they can predict such things precisely and repeatedly is a charlatan or a crank.
- What seismologists can do is identify places where there is a high probability of a strong earthquake happening in the future. On average, there are 18 killer quakes of magnitude 7.0 or greater around the world each year. Most occur along the “Ring of Fire”, a belt of seismic and volcanic activity around the Pacific rim that includes California and Japan.
- Seismologists know, for instance, that similar magnitude 6.0 earthquakes have occurred at regular intervals along the San Andreas fault in California—probably the most intensely studied fault in the world. What they cannot say is precisely when and where the next one will strike. The last time seismologists were bold enough to attempt a forecast, the earthquake came at the designated place but 12 years after the four-year prediction window had closed.
- With his own interests at heart, your correspondent has been keen to help researchers gather information about such possible earthquakes. His curiosity was sparked by the Quake-Catcher Network (QCN) when it was launched in early 2008 by seismologists from the University of California, Riverside, and Stanford University.
- The original aim was to supplement seismic data from 800 permanent monitoring stations around California with information fed back from volunteers with Apple or Lenovo laptops that contained accelerometers to protect their hard-drives if dropped. The researchers imagined the accelerometers would also make handy monitors for detecting ground movement caused by an earthquake, which could then be fed to the network along with the laptop-owner’s location.
- Unfortunately, put to the test last July, when a shock of magnitude 5.4 rattled a large swath of your correspondent’s neck of the woods, only half a dozen of the 1,500 or so laptops signed up sensed any shaking. No more than three sent back data clean enough to use.
- Laptops make poor seismographs because, unless they are nailed down, any quake worth its salt—and of interest to the QCN researchers—would move the computer bodily along with its sensitive accelerometer, making nonsense of its seismic reading.
- The QCN organisers have learned from their mistakes and now offer a separate accelerometer that can be screwed to the floor and attached to any computer with a USB cable. Readers wishing to take part in the quake-catching experiment should visit the organisers’ website for details of the software and sensor.
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