Regional gravity decrease after the 2010 Maule (Chile) earthquake indicates large-scale mass redistribution

Abstract

We report small but detectable changes in the GRACE satellites' relative trajectory after the M8.8 Maule, Chile earthquake on 27 February 2010 that can be used to delineate the shift in the gravity field. A gravity anomaly of -5 μ Gal with a spatial scale of 500 km was found east of the epicenter after the earthquake. Based on coseismic models, the long-wavelength negative gravity change is primarily the result of crustal dilatation as well as surface subsidence in the onland region. The offshore positive gravity anomaly predicted from finite fault coseismic models is considerably smaller because the gravity changes due to surface uplift and interior deformation are opposite in polarity. Our study suggests a role for large-scale gravity observations in deciphering changes of the Earth's interior during great earthquakes by filling in the seldom-observed long-wavelength spectrum of earthquake deformations as a complement to surface geodetic measurements and seismic data. © 2010 by the American Geophysical Union.