Seismic Structure of the Transition Zone Associated with the Japanese Subduction Zones

本次研究的目的是研究400 ~ 700 km深度上地幔过渡带的地震结构，这是了解地幔内部对流方式和地球化学成分的关键。在这个项目中，计划将利用在区域台站记录的上地幔三叠P和S波形来描绘与日本俯冲带相关的过渡带的地震结构。最近将讨论三个主要问题：1)过渡带中俯冲带与何种速度异常有关；2)俯冲板块是在过渡带底部变平还是向下地幔延伸；3)上地幔的地震构造是否支持化学分层模型，还是由于大约在410 km处，可能在525 km处，温度相关的相变而导致的不连续模型。

9526678 Tajima This research is to investigate the seismic structure of the upper mantle transition zone, from 400 to 700 km depth, which is key to understanding the mode of convection within the Earth's mantle as well as the chemical composition of the Earth. In this project, the plan will be to delineate seismic structure of the transition zone associated with Japanese subduction zones using upper mantle (triplicated P and S waveforms recorded at regional stations. Three major issues debated recently will be considered: 1) what velocity anomalies are associated with the subduction zones in the transition zone; 2) whether the subducting slabs flatten at the bottom of the transition zone or extend into the lower mantle; and 3) whether the seismic structure derived for the upper mantle supports a model of chemical layering or one with discontinuities due to temperature-dependent phase transitions approximately at 410 km, and possibly at about 525 km. *** ??