[S-SS11] Seismic wave propagation: Theory and Application

[SSS11-P13] On the estimation of G discontinuity in the oceanic upper mantle using ScS reverberations

*Jumpei Maruyama¹, Hitoshi Kawakatsu¹, Nozomu Takeuchi¹ (1.University of Tokyo, Earthquake Research Institute)

Keywords:ScS reverberations, G discontinuity, lithosphere-asthenosphere system, northwest Pacific

On the upper mantle shear wave velocity structure in the northwestern Pacific, there is a disagreement between the estimations using ScS reverberations (Bagley et al. 2009) and Rayleigh waves (Isse et al., 2019). This may be ascribed to the difference between the sensitivities of these waves to η_κ, the new fifth parameter of VTI (Kawakatsu, 2016), and reflect a characteristic of anisotropy in the oceanic lithosphere-asthenosphere system (LAS).

The method used by previous work (Revenaugh & Jordan, 1991) employs two-step analysis: 0th order analysis for whole mantle parameters and 1st order analysis for the characteristics of mantle discontinuities. Since this method was introduced to investigate the land area of the western circum-Pacific, there has been no detailed verification if it is compatible for the oceanic area whose upper mantle structure significantly differs from that of the continental area. We applied a simplified analysis method to full wave synthetic waveforms generated for an oceanic model with G, and revealed that the conventional method might fail in estimating the upper mantle structure and the whole mantle quality factor Q because of a strong reflected wave from G.

We will attempt to improve ScS reverberation analysis method and to compare its result for the northwest Pacific area with the existing model.