 Map: U.S. Geological Survey |
The 8.8 magnitude earthquake that less than two weeks ago shook Chile and many other places up and down the Pacific coast may have shortened our day length by 1.26 microseconds and shifted Earth’s axis by 3 inches (8 centimeters), according to NASA. The earthquake may also have caused the city of Concepción, Chile’s second largest after Santiago and the one closest to the epicenter, to physically move 10 feet west, Discover reported.
First, the day length and axis: Richard Gross, a scientist at NASA’s Jet Propulsion Lab used what the government body calls a complex model to calculate the quake’s effect, the same tool used to determine these numbers for the 2004 9.1-magnitude earthquake in Sumatra. For comparison’s sake, the model determined that the ’04 quake may have shortened day length by 6.8 microseconds, more than five times the current estimate for the Chilean quake. (A microsecond is one-millionth of a second.) But despite its greater strength, it shifted the figure axis—which NASA defines as the one about which the Earth’s mass is balanced—2.76 inches (7 centimeters), almost a quarter-inch less than the Chilean quake.
Gross gives a couple reasons for the discrepancy:
1. Location. The Chilean quake occurred in mid-latitudes rather than near the equator, making it more effective at affecting figure axis.
2. Fault angle. The fault that caused the 2010 quake was slightly steeper, making it better at moving Earth’s mass vertically and changing the figure axis.
Now, the location: A team of scientists, lead by Mike Bevis, from Ohio State University’s School of Earth Sciences, studied GPS images from before and after the quake. They found that Concepción had physically moved 10 feet west; Santiago moved almost 11 inches west-southwest. Buenos Aires, Argentina, located 800 miles away from the epicenter, shifted approximately an inch.
Chile has seen 13 earthquakes of 7.0 magnitude or greater since 1973, including the largest ever recorded worldwide since the early 20th century, when we began using seismology measuring tools, according to the U.S. Geological Survey. Scientists are working on ways to better predict earthquakes, as senior editor Alisa Opar discussed in her post last week.