Can Japan really predict earthquake ? How ?

CHILL OUT, NO ONE CAN PREDICT EARTH

Workers look toward sea from the bank of Onahama after tsunami warning was lifted, in Iwaki, Fukushima prefecture, northeastern Japan, Tuesday, Nov. 22, 2016. Coastal residents fled to higher ground as a powerful earthquake sent a series of moderate tsunamis toward Japan's northeastern shore Tuesday and fueled concerns about the Fukushima nuclear power plant destroyed by a much larger tsunami five years ago. (AP Photo/Shizuo Kambayashi)AP

THE RING OF Fire is a belt of tectonic plates around the Pacific Ocean. It skirts along the coasts of North and South America, New Zealand, and Japan. And all along, it is gnashing and colliding, creating earthquakes small and large.

On Tuesday, it erupted with two particularly large ones. In New Zealand, a 5.6 tremor hit the country’s North Island. Three hours earlier—and more than 5,000 miles away—a 6.9 magnitude quake hit off Japan’s northeast shore—Fukushima prefecture, site of the 9.1 2011 Tōhoku megaquake. The two quakes probably aren’t related. But the fact that both island nations lie along such earthquake prone regions really makes you wonder why neither saw these quakes coming.

Japan touts the most advanced earthquake warning system in the world. The government spent big bucks implementing a network (California’s en route to implementing a similar one) that detects precursor waves that happen when faults begin to slip. That means the warning system gives notice after the primary waves, but before the destructive seismic shaking—secondary waves. The Japanese Meteorological Agency has about a thousand hardware sensors spread across the country’s four major islands.

The early warning system doesn’t operate alone, though. Seismologists also use the so-called Omori law to calculate how long aftershocks will occur after a big earthquake. It’s been five years, but Japan’s Tuesday temblor is likely an aftershock to the destructive 2011 Tōhoku earthquake. The sequel occurred just 80 miles southwest of Tōhoku’s epicenter—enough to give geologists second thoughts about their interrelatedness. “It’s a response to the stress continuing to readjust to that earlier quake,” says Doug Givens, a geophysicist with the US Geological Society.

So the Omori curve helps geologists calculate whether any given activity their early warning system detects is preamble to a large quake, or just some benign seismic stress relief leftover as an aftershock. But even with the calculations and a state-of-the-art warning system, there was no way the JMA could have had longer term predictions for Tuesday’s quake. At best, their alerts give people a minute to duck and cover before the ground wreaks havoc.