[S-IT19] Deep Earth Sciences

[SIT19-08] Inferring 3-D S- and P-velocity structure of D″ beneath the Central America using waveform inversion

*Rei Sato¹, Yuki Suzuki², Kenji Kawai¹ (1.University of Tokyo, 2.Tokyo Institute of Technology)

D″, the lowermost layer of the Earth’s mantle, is one of the main regions which contain thermal or chemical composition anomalies and is important to understand the Earth’s thermal and chemical evolution. Two theories explaining the chemical evolution of D″ are mainly suggested; (i) chemical differentiation caused by partial melting at thermal boundary layer; (ii) mid ocean ridge basalt segregate from slabs and cumulate above the core-mantle boundary. Therefore, structure estimation at high-resolution, at least which can resolve subducted slabs; ~100km resolution, is required to search the factor of chemical composition anomaly. In order to distinguish thermal and chemical composition heterogeneity, it is necessary to infer the S- and P- velocity structure with comparable resolution using the same quality data. In this study, we expand waveform inversion to estimate S- and P-velocity structure simultaneously at high-resolution (horizontally ~250km and vertically ~100km). Then, we invert the USArray dataset for the 3-D S- and P-velocity structure of D″ beneath Central America. Furthermore, we introduce “mantle correction” to exclude the effect of the 3-D heterogeneous structure except for D″. We will show the inferred models and the result of resolution tests.