Rupture behaviors of the 2011 Tohoku earthquake and its strongest foreshock through an empirical Green’s function deconvolution analysis

• We investigate the rupture history of 2011 Sanriku-Oki and 2011 Tohoku earthquakes.
• Characteristics of large subduction events around the Tohoku region were discussed.
• The rupture prefers a rapid down-dip motion toward the deep region.

An empirical Green’s function (EGF) deconvolution analysis was applied to study the source characteristics of the 2011 Mw 9.0 Tohoku and 2011 Mw 7.4 Sanriku-Oki earthquakes. For the 2011 Tohoku earthquake, we demonstrate that nucleation released weak but high-frequency energy and that the rupture propagated downward and sped toward the deep region after the up-dip slip extended to the trench. Moreover, the 2011 Sanriku-Oki earthquake results and a previous study on the 1994 Sanriku-Oki earthquake suggest that large earthquakes in the subduction zone around the Tohoku area prefer to rapidly rupture toward the deeper (down-dip) region.