Toward comparable relative locations between the mainshock slip and aftershocks via empirical approaches

Abstract

The relative locations between mainshocks and their aftershocks have long been studied to characterize the mainshock–aftershock relationships, yet these comparisons may be subjected to biases inherited from various sources, such as the analysis method, data, and model parameters. Here, we perform both a relocation analysis of interplate events to obtain accurate relative centroid locations and a slip inversion analysis of the mainshock slip relative to the relocated events, with some of the relocated events used as empirical Green’s functions, to retrieve the spatiotemporal slip features of the mainshock relative to all of the relocated events. We perform these analyses on the large (6.0 le M_{W} le 7.3) interplate earthquakes that occurred near four giant (M_{W} ge 8.5) megathrust earthquakes: the 2007 M_{W} ;8.5 Bengkulu (Indonesia), 2005 M_{W} ;8.6 Nias (Indonesia), 2010 M_{W} ;8.8 Maule (Chile), and 2011 M_{W} ;9.1 Tohoku-Oki (Japan) earthquakes. Most of the spatiotemporal slip features of the mainshocks are consistently recovered using different empirical Green’s functions. We qualitatively and quantitatively demonstrate that the large interplate aftershocks within 5 years of the four analyzed mainshocks are largely located on the periphery or outside of the large-slip regions of these four giant megathrust earthquakes.