GPS Study of Chile's Megaquake Shifts Epicenter 40 Kilometers
May 12, 2011Using data from more than 20 GPS stations, researchers in France relocated the epicenter of the 8.8-magnitude earthquake that struck off the coast of southern Chile on February 27, 2010, by 40 kilometers (25 miles).
In a study published online by Science magazine, the researchers conclude that the earth ruptured at about three kilometers per second.
“We analyzed cGPS (continuous GPS) and survey GPS data from before, during, and after the Maule event to determine the deformation of the Earth’s surface close to the earthquake rupture,” wrote Christophe Vign of the Laboratoire de Geologie de l’ENS in Paris, who is lead author of the study. “We use data from Global Positioning System networks in Central Chile to infer the static deformation and the kinematics of the 2010 megawatt 8.8 Maule mega-thrust earthquake. From elastic modeling, we find a total rupture length of ~500 km where slip (up to 15 m) concentrated on two main asperities situated on both sides of the epicenter. We find that rupture reached shallow depths, probably extending up to the trench.
“The low frequency hypocenter is relocated 40 km southwest of initial estimates," the authors conclude. "This epicenter is different from those reported by seismological services. It is located 15 km south of the epicenter by the Servicio Sismologico Nacional (SSN) of the University of Chile and is almost 40 km southwest of the epicenter reported by NEIC (the USGS National Earthquake Information Center).”
The scientists also found that vertical displacements reached 1.8 meters of uplift at the tip of the Arauco peninsula, the land point closest to the trench.
The full article, "The 2010 Mw 8.8 Maule Mega-Thrust Earthquake of Central Chile, Monitored by GPS," is available through Science magazine. GEO's Chile Event Supersite provides additional information. Also, see the Related Links below.
Co-seismic static displacement field derived from cGPS sites (Click to enlarge.)
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