| At least 3 major aftershocks rocked central Chile several hours ago, striking minutes before its president-elect was sworn into office to take charge of a country still reeling from a devastating earthquake nearly two weeks ago. The first of the three major aftershocks hit at 11:39 a.m., with a magnitude of 7.2. It the strongest to hit since Chile was ravaged by an 8.8-magnitude quake on Feb. 27. Tsunami Alert: Chile's Navy rapidly issued a tsunami alert, and Chilean television carried reports of residents of coastal areas fleeing for higher ground. There were no immediate reports of damage, but in the capital of Santiago, 95 miles north of the epicenters, windows rattled, buildings trembled and cell phone service went down. The U.S. Geological Survey reported that the quake struck the coast near the city of Rancagua, and was quickly followed by one of 6.9 magnitude at 11:55 a.m., and another of 6.0 magnitude at 12:06 p.m.Scores of strong aftershocks have rattled Chile's interior and its coastline since one of the most powerful earthquakes on record, at magnitude 8.9, devastated the country on Feb. 27. It was this quake which killed hundreds of people, toppled apartment buildings and bridges, and stirred up powerful waves that wiped away entire fishing villages as they pounded the southern coast of the country. Andrea Thompson LiveScience Senior Writer LiveScience.com andrea Thompson livescience Senior Writer livescience.com - 31 mins ago The whopping 7.2-magnitude aftershock that rattled Chile again today is nothing unusual following such a large original earthquake, scientists say. The aftershock, which struck at about 11:40 am local time, may sound surprisingly strong, given that it is bigger than the original earthquake that decimated Haiti in January, but it wasn't unexpected to scientists, said Don Blakeman, a geophysicist with the United States Geological Survey. The 8.8-magnitude earthquake that struck off the coast of the Maule region of Chile on Feb. 27 was one of the strongest ever recorded. After such a strong quake, aftershocks that are themselves substantial are par for the course. Aftershocks are typically smaller in magnitude than the original quake, with many small aftershocks and a handful of larger ones. With an original quake that was more than an 8 in magnitude "we would expect at least a couple of 7's," Blakeman told LiveScience. Aftershocks are earthquakes themselves that occur because the fault that ruptured in the original temblor is still readjusting itself. They typically occur within the same zone along a fault that ruptured in the original quake. And "the bigger the quake, the larger the aftershock zone," Blakeman said, which explains why this aftershock was not in the same spot as the epicenter of the original earthquake. The rupture zone for the original quake was 250 miles (400 kilometers) long, "so it's a very big zone," Blakeman said. The aftershock struck about 93 miles (150 km) southwest of the capital, Santiago. Aftershocks can last for weeks to months. They may not occur continuously, with periods of quiet in between sequences of aftershocks. "It kind of runs in spells," Blakeman said. Not long after the 7.2-magnitude aftershock today, a powerful 6.9 aftershock shook the area again. So far, the original Chile earthquake has spawned just the one aftershock over a 7 in magnitude and about 10 in between a 6 and a 7, Blakeman said. But "I know we've had at least 150 in the 5 or greater range," he added. And such a large magnitude aftershock guarantees that "you'll have a lot more after that," Blakeman said. "It's like this aftershock will have its own aftershock." And even though it's getting further away in time from the original earthquake, the magnitude of aftershocks won't necessarily dissipate. "We could certainly have more in the 7 range," Blakeman said. |