The powerful magnitude 8.8 earthquake that rocked Chile was strong enough to shift the planet's axis by 3 inches, and came soon after the catastrophic magnitude 7.0 quake that devastated Haiti and right after a magnitude 7.0 event hit off the coast of Japan.
Where might earthquakes hit next? Earth scientists might not be able to give us a date and time, but using history and plate tectonics as a guide they can come up with some rough estimates as to where.
Eurasia
The landmass making up Asia and Europe is confronted with the two most seismic regions in the world — to its west, it has the Pacific Ring of Fire, and to its east, it has the Alpine-Himalayan Zone.
Both of these areas mark plate boundaries, where tectonic plates crash together, spread apart or slip past one another. These boundaries and the faults related to them are responsible for roughly 99 percent of the earthquakes people face, explained seismologist Chris Scholz at Columbia University's Lamont-Doherty Earth Observatory.
The earthquakes that regularly jolt Japan and California stem from the Ring of Fire, as did the latest Earthquake in Chile. "The Ring of Fire goes all the way from the Philippines past Japan to China and Kamchatka in Russia, to the Aleutians in the United States down through Alaska and across Cascadia in the Pacific Northwest, joining up with the San Andreas down the West Coast to Mexico and into South America, and another part of the ring goes through Indonesia," Scholz said.
The Tokai Gap of Japan should rupture every 150 or so years for a magnitude 8.0 earthquake — "it last ruptured in 1856, and it's overdue," he added. "They're expecting their next big one there."
The Alpine-Himalayan Zone and the faults related to it are linked with the 2008 Sichuan quake in China, the 2005 quake in Kashmir and the 1999 Izmit quake in Turkey, as well as the earthquakes that often rock Italy. "The Alpine-Himalayan Zone goes through India, Tibet and China, down to Burma and across to the Middle East, where it breaks up into a million small pieces, and then over to the Mediterranean," Scholz said.
Africa
Africa is ripping apart along a 2,400-mile crack named the East Africa Rift, which stretches from the Red Sea to Mozambique. This giant continental tear started in the north some 25 million years ago and has been gradually unzipping to the south, apparently on the way to splitting the African Plate into two new tectonic plates.
This developing plate boundary has given rise to a number of volcanoes, including famed Mount Kilimanjaro, created huge depressions that are now filled by some of the largest and deepest lakes in the world, and generated massive faults that regularly lead to earthquakes, such as the magnitude 7.0 that hit Mozambique in 2006.
The Americas
The Americas face the Pacific Ring of Fire to their west. The section of the San Andreas fault known as the 1857 earthquake rupture zone should break every 200 to 250 years for a magnitude 8 earthquake, Scholz said. "Sometime this century, it's likely to break again," he noted.
To the east, the boundary between the Caribbean and North American plates gave rise to the recent quake that hit Haiti. A number of ancient faults also go from Canada all the way at least to South Carolina, including near New York. The largest earthquake in the northeast was probably the Cape Ann earthquake in 1755 off the coast of Massachusetts, which might have been a magnitude 5.9 quake.
Three of the largest earthquakes recorded in North America actually originated from the New Madrid fault system in the center of the United States. Over the course of two months from 1811 to 1812, these magnitude-7 events shook with enough power to apparently force the Mississippi River to temporarily flow backward. Such intra-plate earthquakes make up some 1 percent of the quakes people face, Scholz said, and are much less understood than the others.
"These are always surprising when they go off, and can cause a lot of damage if in populated areas," he said.
Australia
Australia mostly sees only small quakes, although Newcastle, its sixth largest city, did see a moderate earthquake measuring 5.6 on the Richter Scale in 1989 — the first recorded lethal one in the country, claiming 13 lives. Australia lies in the middle of a tectonic plate (rather than at the boundary between two plates), and research is ongoing into such intra-plate earthquakes.
Predicting the big one
Is there any way one might predict such quakes before they happen?
"All earthquakes are difficult to impossible to predict with respect to their location and exact time," said seismologist Susan Schwartz at the University of California, Santa Cruz. "However, based on previous earthquake behavior in a region, we can provide probabilities of earthquakes of different magnitudes occurring within certain time periods. It was known that this section of the Chile coastline has had very large earthquakes in the past and would again sometime in the future."
Still, "in the short-term sense that most people think — predicting earthquakes weeks or months ahead, or the location or size of an earthquake that's going to happen — we don't know yet if we can do that or not," Scholz said.
Scientists are working on ways to make such predictions, scientifically testing algorithms that might be able to do so, said geologist Ramon Arrowsmith at Arizona State University.
"It's a very hard scientific problem," Scholz noted. "We don't know if it's a problem that can be solved."
With reporting by Jeanna Bryner.
