[S-IT22] [EE] 核-マントルの相互作用と共進化

[SIT22-11] Waveform inversion for whole mantle 1-D S-velocity and Q structure beneath Central America and the Caribbean

*Anselme F. E. Borgeaud¹、Kenji Kawai¹、Robert J. Geller¹、Kensuke Konishi² (1.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo、2.Institute of Earth Sciences, Academia Sinica)

キーワード：Waveform inversion, Earth's mantle, Anelastic structure

We simultaneously infer the 1-D S-velocity and anelastic (Q) structure in the whole mantle beneath Central America using waveform inversion. Our dataset consists of ~8000 transverse components recorded at USArray broadband stations from ~40 intermediate- and deep-focus events in South America. We use waveforms in time windows cut around the minor arc arrivals which include body-wave arrivals (e.g. Sn, sSn) as well as multiple reverberations at the core-mantle boundary (ScSn, sScSn). These data provide constraints on the difference in Q structure between the upper- and lower-mantle. We use the Born approximation to compute partial derivatives for 1-D shell perturbations at depth increments of 20 km in the whole mantle. Our model is parametrized in radial splines formed by linear combination of those 20 km-increment perturbations. Synthetic tests suggest that our dataset and method can simultaneously resolve the 1-D S-velocity and Q structure in the whole mantle. Knowledge of both the S-velocity and Q structure can help to provide constraints on the origin of the S-velocity anomalies, i.e., whether they are of thermal or chemical origin.