First detection of absolute gravity change caused by earthquake

Abstract

Unequivocal coseismic gravity change was detected for the first time by absolute gravimetry. The measurements were done just one day before and only 7 days after a M6.1 earthquake (M6.1). The absolute gravity change was −6 microgal, significantly larger than the observational error of about 1 microgal. Of particular interest is that the observed spatial gravity variations agree remarkably well with those expected from an elastic dislocation model constructed on displacement data alone. The result strongly encourages us to perform a simultaneous inversion of both gravity and displacements to have better insight of earthquakes.