15:30 〜 15:45
[SIT18-06] 波形インバージョン法を用いた太平洋北東部下の外核最下部の1次元P波速度構造推定
キーワード：液体構造の波形インバージョン、外核最下部、実体波
In the lowermost outer core, immediately above the inner core boundary (ICB), the crystallization of liquid iron releases light elements into the outer core, which is thought to drive outer core convection. Therefore, this layer is one of the most important regions in understanding the Earth’s thermal and chemical evolution. For a better understanding of the distribution of light elements, it is important to estimate the detailed structure of the lowermost outer core. In seismology, a low-velocity anomaly layer is suggested to exist in the lowermost outer core, but its thickness and velocity gradient are controversial (Souriau & Poupinet, 1994; Kennett et al., 1995; Yu et al., 2005; Ohtaki & Kaneshima, 2015). This is because many previous seismological studies face challenges due to the limited number of seismic data sensitive to the lowermost outer core.
Our research group has developed methods for localized waveform inversion (Kawai et al., 2006), which can fully utilize waveforms themselves as the data, enabling high-resolution imaging of mantle structure. This method can resolve the limited number of data by extracting all information from seismic waveforms and using data with close travel times, which contain detailed information about the lowermost outer core.. In this study, therefore, we extend the waveform inversion technique to infer the liquid structure. We also apply this extended method to data including the PKP, PKiKP, and PKIKP phases to estimate the 1-D P-wave velocity structure of the lowermost outer core beneath the northeastern Pacific, where the seismic data sampling is abundantly provided by NIED and IRIS. In this presentation, we will show the inferred 1-D P-wave velocity model and the resolution test result.
Our research group has developed methods for localized waveform inversion (Kawai et al., 2006), which can fully utilize waveforms themselves as the data, enabling high-resolution imaging of mantle structure. This method can resolve the limited number of data by extracting all information from seismic waveforms and using data with close travel times, which contain detailed information about the lowermost outer core.. In this study, therefore, we extend the waveform inversion technique to infer the liquid structure. We also apply this extended method to data including the PKP, PKiKP, and PKIKP phases to estimate the 1-D P-wave velocity structure of the lowermost outer core beneath the northeastern Pacific, where the seismic data sampling is abundantly provided by NIED and IRIS. In this presentation, we will show the inferred 1-D P-wave velocity model and the resolution test result.