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1
On 11 March 2011, a deadly earthquake struck
near Tohoku, on Japan’s east coast. With a magnitude of 9.0, it was one of the
most powerful earthquakes ever recorded. It caused a tsunami that killed
thousands of people and destroyed the Fukushima-Daiichi nuclear power plant. Japanese
scientists were shocked: they had assumed that an earthquake of that size could
not strike Tohoku. Outside Japan, three other large earthquakes caused major destruction—one
in China in 2008, and two others in New Zealand in 2010 and 2011. All occurred
in areas that scientists thought were relatively safe.

2
Clearly, earthquake prediction is very difficult. So what can we predict? Scientists can calculate the chances that big
earthquakes will strike in a large area during a period of years, but that is too
vague to be very helpful. Early warning systems can measure the first tremors of
an earthquake, alerting people in the area and allowing them a few vital seconds
to respond. But what scientists really want to do is predict the time, place,
and strength of an earthquake. Why is that proving so difficult?

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3
Imagine a brick sitting on a desk, attached to a rubber band. Start to pull on
the band. Because the rubber is elastic—just like the Earth’s crust—the brick
doesn’t slide smoothly. Instead, the band stretches until, suddenly, the brick moves
forward. That’s an earthquake. However, there are many factors involved—including
the mass, friction and elasticity of the Earth’s plates—and they all vary
greatly. The result is something that’s incredibly difficult to predict.

4
Perhaps if we have enough data, we can make accurate predictions? A group of
scientists in California tried to do that in the 1980s. The team set hundreds
of measuring devices in a small part of the San Andreas fault. The researchers
wanted to find signals that the next earthquake was about to happen. But when
the earthquake finally happened in 2004, the instruments saw nothing. The problem
was that the fault line is long and there are eight kilometers of rock between
the surface and what scientists want to study. To get readings across its
entire area would take hundreds of thousands of drill holes. It is an almost
impossible task.

5
Certain things happen before an earthquake that could help us make better
predictions. Animals act strangely; gas is released from rocks; electromagnetic
signals come from rocks under pressure. Studying these events may help our
understanding of earthquakes, but can they help us predict the timing and
location of an earthquake? According to Ross Stein from the United States Geological
Survey, “that effort is not worth pursuing. We have 30 to 40 years of negative
results to convince us that this isn’t a good investment of resources.” Some
scientists believe that earthquake prediction is simply impossible—the factors
are so numerous and so complex that trying to measure and analyze them is not
worthwhile.

6
If we cannot predict major earthquakes, we might have more success predicting their
aftershocks. This is extremely important as the aftershocks can be as
destructive as the primary earthquake. One thing that we can do is predict the
frequency of aftershocks. Ten days after a main earthquake, the frequency of
aftershocks falls by a factor of ten; a hundred days later, aftershocks are 100
times less frequent. Stein and other scientists are trying to understand where these
aftershocks are most likely to occur, and they are making progress. They are
simulating what happens to fault lines and how they are affected when the main
earthquake happens; they can then use that knowledge to predict where the
aftershocks will occur.

7
Imagine a future when earthquake prediction is accurate. Even then, we would
still need evacuation plans and earthquake-proof buildings to prevent disaster.
Good plans, a well-prepared public, and buildings that are built to withstand
earthquakes will all save lives; focusing on these may therefore be a more
effective use of public money. Japan-based earthquake expert Robert Geller
agrees. “All of Japan is at risk from earthquakes,” he points out. “We
should instead tell the public and the government to prepare for the
unexpected.” Is it perhaps time to stop trying to predict the unpredictable?

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