Geo-center movement caused by huge earthquakes

In this study we investigate co-seismic geo-center change based on a dislocation theory for a spherically symmetric, non-rotating, perfectly elastic and isotropic model. We first introduce the basic theory with emphasis on the dislocation Love numbers of degree 1, and then we present methods for computing co-seismic geo-center movement. It is found that the geo-center change reaches maximum value when δ = 45° and λ = 90°, i.e., a 45° declined dip fault causes the maximum geo-center movement. As an application, we apply the methods to compute the geo-center movement caused by the 2004 Sumatra earthquake (Mw9.3) and the 2011 Tohoku-Oki earthquake (Mw9.0). Results show that the maximum co-seismic geo-center movements for the two events are 0.87 mm and 0.43 mm, respectively.