Earth's Journal

Geosphere Journal Entry

Massive Earthquake Strikes Chile (March 1, 2010)

Chile qke

The bulls-eye is the epicenter of the violent earthquake in Chile. The purple line is the tectonic plate boundary between the Nazca and South American plates. USGS.

A massive earthquake registering magnitude 8.8 struck central Chile, triggering widespread destruction and sending tsunami waves racing across the Pacific Ocean. The deadly quake crumbled buildings, highways, and bridges over a wide area. At least 700 people were killed and over 1.5 million people were displaced. The death toll is expected to climb as more victims are dug from the rubble of collapsed homes, especially in the hard-hit city of Concepcion only 70 miles (110 kilometers) from the quake's epicenter. Shaking was felt as far away as Sao Paulo, Brazil 1,800 miles (3,000 km) away. Dozens of strong aftershocks of up to magnitude 6.9 kept Chileans on edge and made rescue work dangerous in the quake's aftermath. The catastrophic quake is the most powerful to hit the planet since the 9.0 quake that rocked Indonesia in December 2004.

The quake set off the first hemisphere-wide tsunami warning for the Pacific Basin since 1964. 8-foot waves washed over islands and the coast near the epicenter minutes after the quake struck. The tsunami swamped Robinson Crusoe Island 400 miles (640 km) away within an hour, killing four people. It hit Hawaii with waves up to 6-feet tall about 15 hours later. The next day 4-foot waves washed over parts of Japan's coast, where thousands had already fled their homes, more than 6,000 miles (10,000 km) from Chile.

The earthquake hit at the tectonic plate boundary separating the Nazca and South American plates, where the heavier Nazca plate subducts or dives below the South American plate. It struck along a thrust fault where two slabs of Earth's crust slide vertically past each other. The fault slipped from built-up stress 20 miles (30 km) below the surface. Because it triggers sharp up and down motion, a quake along a thrust fault can push up huge amounts of water and send it racing across the sea at speeds of 500 mph (800 km/h). The fault is the same one that slipped in the monstrous magnitude 9.5 Chile quake of 1960, the most powerful ever recorded.

The Chile quake unleashed far greater energy than the deadly quake that rocked Haiti earlier this year, killing about 230,000 people. The death toll was much lower in Chile thanks to the nation's strict building codes. Chile tightened the codes after suffering through the destruction of a violent 7.8 quake in 1985.