5:15 PM - 7:15 PM
[SIT20-P03] ScS Travel Times of Deep Earthquakes and Plate Subduction
Understanding seismic wave propagation is important for evaluating earthquake damage and understanding the Earth’s evolution. Seismic wave propagation is complex beneath Japan, where multiple plates converge. The structure of the Earth's interior revealed by analyzing seismic waves is useful for understanding how the Earth has evolved over a long period.
Among seismic waves propagating through the Earth's interior, the S waves reflected by the outer core are called ScS waves. ScS waves are sensitive to the discontinuities in the mantle and the core-mantle boundary.
In this study, we first examine how ScS wave arrivals are explained by the 1D velocity structure. We use deep earthquakes around Japan observed at F-net stations. Specifically, we extract forty seconds around the theoretical ScS wave travel time calculated for IASP91, which is a global reference model of seismic wave velocities. The travel time at each station is estimated by comprehensively analyzing the cross-correlation between stations. As a result, we confirmed the effect of the subducting Pacific Plate for the ScS waves observed in Tohoku region for deep earthquakes beneath Bonin Island.
Then, we evaluate the effect of plate subsection quantitatively by comparing the observed ScS arrivals with the synthetic seismograms calculated using the three-dimensional velocity structure obtained in a previous study. Focusing on the travel time and amplitude of ScS waves, we investigate the existence of velocity anomalies.
Among seismic waves propagating through the Earth's interior, the S waves reflected by the outer core are called ScS waves. ScS waves are sensitive to the discontinuities in the mantle and the core-mantle boundary.
In this study, we first examine how ScS wave arrivals are explained by the 1D velocity structure. We use deep earthquakes around Japan observed at F-net stations. Specifically, we extract forty seconds around the theoretical ScS wave travel time calculated for IASP91, which is a global reference model of seismic wave velocities. The travel time at each station is estimated by comprehensively analyzing the cross-correlation between stations. As a result, we confirmed the effect of the subducting Pacific Plate for the ScS waves observed in Tohoku region for deep earthquakes beneath Bonin Island.
Then, we evaluate the effect of plate subsection quantitatively by comparing the observed ScS arrivals with the synthetic seismograms calculated using the three-dimensional velocity structure obtained in a previous study. Focusing on the travel time and amplitude of ScS waves, we investigate the existence of velocity anomalies.