[S-SS33_30PO1] Crustal Deformation

[SSS33-P06] Estimation of frictional parameters in afterslip areas by assimilating GPS data :The 2003 Tokachi-oki earthquake

*Masayuki KANO¹, Shinichi MIYAZAKI², Yoichi ISHIKAWA³, Yoshihisa HIYOSHI³, Kosuke ITO³, Kazuro HIRAHARA² (1.ERI, Tokyo Univ., 2.Kyoto University, 3.JAMSTEC)

Keywords:afterslip, adjoint method, frictional parameters, GPS, earthquake cycle

Seismological and geodetic observations have revealed that various aspects of fault slips are determined by frictional properties on the interface. Kano et al. (2013) developed an adjoint data assimilation method to estimate frictional parameters from synthetic in-situ slip velocity data and found by numerical experiments that all frictional parameters are constrained if both acceleration and deceleration phases are observed. Additionally, we found that synthetic surface displacement data also have the ability to constrain frictional parameters in the areas where slip is well resolved. Following their study, we then applied the method to an actual case of the 2003 Tokachi-oki earthquake. Given reasonable initial conditions of simulation variables, estimated frictional parameters are well constrained if two conditions above are satisfied. Our results imply that the adjoint method we developed is useful to investigate and understand fault frictional properties.