12:00 PM - 12:15 PM
[SIT14-11] Constraining thermal and chemical heterogeneity in D″ beneath Central America based on waveform inversion for 3-D S- and P-velocity structure
Keywords:waveform inversion, D″ region, lowermost mantle, body wave, subducted slab
The lowermost mantle region (D″) just above the core-mantle boundary (CMB) is the thermal boundary layer of mantle convection and the boundary layer where the core-mantle interaction occurs. Estimating the thermal and chemical structures in D″ leads to a better understanding of the Earth’s thermal and chemical evolution. Therefore, it is necessary to infer the S- and P-velocity structures with comparable high (at least 100 km vertically) resolution using the same quality data and to distinguish thermal and chemical effects.
In this study, using the waveform inversion method, we try to infer the 3-D S- and P-velocity structures in D″ beneath Central America at a high resolution (~ 250 km horizontally and ~ 50 km vertically). We assembled a dataset of three waveform components from deep- and intermediate-focus South American, Caribbean, and Alaskan events mainly recorded at the full USArray network stations. Our preliminary model showed that we resolve S-velocity structures well in the whole parts of D″ thanks to the three-component data, suggesting the paleo-Farallon slab exists in the whole parts of D″. In contrast, we resolve the P-velocity structure in smaller areas than the S-velocity structure because of the paucity of available PcP data.
Sensitivity analysis demonstrated that the later half wavelength of the direct P-phase mainly contributes to the resolution of the P-velocity structure in D″. Therefore, we gather the additional waveform data from shallower and weaker events containing the direct P-phase in order to obtain a better resolution of the P-velocity structure. In the presentation, we will show the inversion results with additional data and the feasibility of the inversion using the direct P-phase with quantitative resolution tests and discuss their geophysical implication.
In this study, using the waveform inversion method, we try to infer the 3-D S- and P-velocity structures in D″ beneath Central America at a high resolution (~ 250 km horizontally and ~ 50 km vertically). We assembled a dataset of three waveform components from deep- and intermediate-focus South American, Caribbean, and Alaskan events mainly recorded at the full USArray network stations. Our preliminary model showed that we resolve S-velocity structures well in the whole parts of D″ thanks to the three-component data, suggesting the paleo-Farallon slab exists in the whole parts of D″. In contrast, we resolve the P-velocity structure in smaller areas than the S-velocity structure because of the paucity of available PcP data.
Sensitivity analysis demonstrated that the later half wavelength of the direct P-phase mainly contributes to the resolution of the P-velocity structure in D″. Therefore, we gather the additional waveform data from shallower and weaker events containing the direct P-phase in order to obtain a better resolution of the P-velocity structure. In the presentation, we will show the inversion results with additional data and the feasibility of the inversion using the direct P-phase with quantitative resolution tests and discuss their geophysical implication.