11:45 〜 12:00
[SIT16-05] Constraining 3-D S- and P-velocity structure of D″ beneath the Central America from multiple component data using waveform inversion
キーワード：波形インバージョン、D″領域、マントル最深部、実体波、沈み込みスラブ
D″, the lowermost layer of the Earth’s mantle, is one of the main regions which contain thermal or chemically compositional 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 the thermal boundary layer; (ii) mid-ocean ridge basalt (MORB) segregates from slabs and cumulates above the core-mantle boundary. Therefore, structure estimation at a high resolution, at least which can resolve in the D″ region, vertically ~100km resolution, is required to search the factor of chemical anomalies. In order to distinguish thermal and chemical effects, it is necessary to infer the S- and P- velocity structure with comparable resolution using the same quality data.
In this study, aiming to infer S- and P-velocity structure simultaneously at a high resolution (horizontally ~250km and vertically ~50km), we first conduct localized waveform inversion using transverse (T) and vertical (Z) components of the waveforms from South American, Caribbean, and Alaskan events recorded at the full USArray network stations and estimate the 3-D S-velocity structure in D″ beneath Central America. The inversion results show that we improve the resolution of the S-velocity structure, especially in the shallower part of D″ with two components. Second, we extend the waveform inversion method and try to constrain both 3-D S- and P-velocity structures using the same dataset. Our results indicate that we can resolve the P-velocity structure in the region densely sampled by P-wave. Our inferred models suggest the existence of the paleo-Farallon slabs and the Fe, Al-rich regions in which piles of the MORB may form. To enhance the resolution of the P-velocity structure, we improve the dataset. Our presentation will show the results with the improved data.
In this study, aiming to infer S- and P-velocity structure simultaneously at a high resolution (horizontally ~250km and vertically ~50km), we first conduct localized waveform inversion using transverse (T) and vertical (Z) components of the waveforms from South American, Caribbean, and Alaskan events recorded at the full USArray network stations and estimate the 3-D S-velocity structure in D″ beneath Central America. The inversion results show that we improve the resolution of the S-velocity structure, especially in the shallower part of D″ with two components. Second, we extend the waveform inversion method and try to constrain both 3-D S- and P-velocity structures using the same dataset. Our results indicate that we can resolve the P-velocity structure in the region densely sampled by P-wave. Our inferred models suggest the existence of the paleo-Farallon slabs and the Fe, Al-rich regions in which piles of the MORB may form. To enhance the resolution of the P-velocity structure, we improve the dataset. Our presentation will show the results with the improved data.