Study on Temporal Variations of S Wave Anisotropy in the Mantle.

为了研究D”层S波偏振各向异性特征快速变化的可能性，我们分析了日本周边地区深震辐射的ScS波分裂和日本的台站记录。所用的地震记录是日本气象厅和几所大学提供的。包括我们和其他研究人员以前报道的结果，我们得到了35个方位角的各向异性主轴在过去的三十年。方位角的时间变化表明，主轴方向至少在十年量级上不随时间变化。然而，数据表明，有可能在一个较长的时间内的轴方向的时间变化。

In order to study the possibility that features of the S wave polarization anisotropy in the D" layer change quickly, we analyze the splitting of ScS waves which are radiated from deep earthquakes around Japan and recorded stations in Japan. The used seismological records are those obtained by Japan Meteorological Agency and several universities. Including results reported previously by us and other researchers, we obtain 35 azimuths of the anisotropic pricipal axes for the last three decades. The temporal variation of the azimuths shows that the directions of pricipal axes do not change with time at least in an order of ten years. However, the data suggests that there is a possibility of the temporal variation of the axis direction in a longer period.