Scientists still can't predict exactly when earthquakes will occur, but the massive temblor that struck off the coast of Chile early Saturday was anything but unexpected. Chile sits on the Ring of Fire, the volatile, 40,000 km-long (25,000 MILE) zone that encircles the Pacific Ocean and includes the most seismically dangerous ground on the planet. The unstable plate tectonics along the Ring produce some 90% of the world's earthquakes as well as most of its volcanic eruptions.
Because the Ring follows the coastlines of Pacific Ocean, almost any major quake can also produce a tsunami, a powerful wave that travels from the epicenter of the temblor across the ocean basin. That's what happened in 2004, when a 9.3-magnitude quake off the Indonesian island of Sumatra triggered a devastating tsunami, and that's is what's likely to happen following today's 8.8-magnitude quake off the coast of Chile.
Temblors in the Ring of Fire are so common that a 7.0-magntitude quake hit Japan's Ryuku Islands yesterday. Today's Chilean quake occurred on one of the more powerful fault lines in the region, where the underwater Nazca Plate in the Pacific gradually submerges beneath the westward moving South American plate. The border between these two plates is known as a thrust fault, and the sudden rubbing of the plates against each other resulted in an earthquake that ripped across an estimated 400 miles of the fault. With a Richter scale magnitude of 8.8, the Chilean quake was nearly 1,000 times stronger than the temblor that hit Haiti last month.
Chile, however, is no stranger to major earthquakes. In 1960, a 9.5-magnitude temblor — the strongest quake ever recorded by scientific instruments — hit the Chilean city of Valdivia, killing nearly 2,000 people. And although today's quake is the strongest in the last half-century to hit Chile, the country has had 13 quakes of 7.0 or higher on the Richter scale since 1973. That geologic history helps explain why building codes are far tougher in Chile than they are in Haiti, which should help limit the number of casualties from today's quake. So far, 147 people have been confirmed dead, but that number is expected to rise.
Because the quake occurred offshore, however, the destruction likely won't be limited to Chile. As the underwater plates shake, they push the water above them up, creating the beginning of a wave, not unlike dropping a stone in a bathtub. The wave then travels away from the epicenter of the quake. In the case of the Chile temblor, the waves are moving in a northwest direction across the Pacific, putting nearly every shoreline along the ocean at some risk.
In open water, a tsunami makes barely a ripple, but as the waves approach a shoreline, they gather strength and height, finally spilling over land.
The waves travel at roughly the speed of a passenger jet, but because of the vast distance they are traveling across the Pacific from Chile's coast, vulnerable islands hours to prepare. That wasn't the case during the 2004 tsunami, which rippled across the much smaller Indian Ocean basin before there was time to raise a proper warning.
Hawaii, which sits squarely in the middle of the potential tsunami's path, also has a sophisticated warning protocol that should get people off the shore in time. By contrast, Indonesia, Sri Lanka and Thailand, the areas hardest hit by the 2004 tsunami, had virtually no alert system.
The fact that the Chilean quake occurred six weeks after the catastrophic temblor in Haiti could lead many to wonder if we're entering a new era of seismological disaster. But the two quakes are unrelated, occurring on different faults. The reality is that Chileans live in one of the most seismically dangerous regions in the world, and an earthquake as powerful as the one that hit this morning was just a matter of time. The question is how Chileans — and the rest of the world — can better prepare for geological calamity.
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