Like fireflies, earthquakes too can fire in synchrony

WASHINGTON - Just like fireflies flashing sporadically in early evening soon flash together in harmony, big earthquakes can trigger other big quakes by transferring stress along a single fault, according to scientists.

The phenomenon was seen in successive earthquakes in Turkey and Indonesia.

In fact, some powerful quakes can set off other big quakes on faults tens of kilometers away, with just a tiny nudge, says the new paper.

Christopher Scholz, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory, explains how the faults are already synchronized.

Scholz argued that when a fault breaks, it may sometimes gently prod a neighboring fault also on the verge of fracturing.

The study finds evidence for synchronized, or “phase locked,” faults in southern California’s Mojave Desert, the mountains of central Nevada, and the south of Iceland.

Drawing on earthquake patterns as far back as 15,000 years, the study identified strings of related earthquakes, and explains the physics of how faults separated by up to 50 kilometers, and rupturing every few thousand years, might align themselves to rupture almost simultaneously.

“All of a sudden bang, bang, bang, a whole bunch of faults break at the same time. Now that we know that some faults may act in consort, our basic concept of seismic hazard changes. When a large earthquake happens, it may no longer mean that the immediate future risk is lower, but higher,” said Scholz.

When a fault ruptures in a large earthquake, the movement releases stresses that may have built up over millennia.

But the movement also transfers a small amount of that stress, usually a fraction of a percent, to nearby faults. In order for that tiny added stress to trigger a large earthquake on a nearby fault, that fault had to already be very near its breaking point, said Scholz.

For the two faults to have been simultaneously near their breaking points requires them to be synchronized in their seismic cycles.

Scholz said that his hypothesis of synchronized faults could make it easier to assess some earthquake hazards by showing that faults moving at similar speeds, and within roughly 50 kilometers of each other, may break at similar times, while faults moving at greatly different speeds, and located relatively far apart, will not.

However, seismologists have yet to come up with a reliable method for predicting imminent earthquakes- the best they can do so far is to identify dangerous areas, and roughly estimate how often quakes of certain sizes may strike.

The study is published in the recent issue of the Bulletin of the Seismological Society of America. (ANI)