5:15 PM - 6:30 PM
[SSS02-P05] Improved fault model of the Tohoku intraslab earthquake on Dec. 2012 (Mw 7.2) and its implication for the post-2011 stress state
Keywords:Tsunami, Doublet earthquake, Intraslab stress state, 2011 Tohoku-Oki earthquake
The aftershock distribution deduced from local OBS observation (Obana et al., 2014, EPS; 2015, AGU), the west-dipping aftershock lineation is clearly shown around the subevent 2, and little aftershocks were identified around the subevent 1. Therefore we compared between the tsunami source model derived from inversion analysis of pressure records and the sea surface vertical displacement expected only from the subevent 2 constraining the fault geomotry based on the aftershocks. In the calculation, we assumed a planar fault with uniform slip and constrained the location, strike and dip of the fault plane based on the aftershock distribution. The depth extent of fault plane was set between the slab surface (~7km) and the lower limit of aftershocks (~40km), and slip amount is given by scaling law and CMT solution. The sea surface displacement is obtained by applying depth filter (Saito and Furumura, 2009, GJI) to the seafloor displacement. As a result, the calculated extent and amount of the subsidence area is mostly comparable to the tsunami source model, suggesting that the subsidence area is created basically from the subevent 2. In the presentation, we will constrain the vertical depth extent of the subfault 2 in more detail considering the difference of the pattern of sea surface displacement associated with the vertical location of the fault slip. We will also constrain the hypocenter of the subevent 1 based on the local OBS network and improve the fault geometry of the subevent 1. Finally we will compare the previous studies of seismicity in this region and discuss the intraslab stress change associated with the Tohoku-Oki earthquake.