中文摘要：

利用泰安台YRY-2型钻孔差应变仪的观测资料，研究了两次印尼苏门答腊地震的环型振荡的剪应变方向。首先对差应变仪观测数据进行实地标定，然后用标定后的数据检测2004年12月26日和2005年3月28日印尼苏门答腊两次大地震激发的环型振荡，发现基频环型振荡0T11～0T18最明显，且两次地震的振幅变化趋势基本一致。两次地震得到的0T11～0T18型环型振荡的最大剪应变方向随时间变化比较小。通过与理论预期的对比，发现实测值的平均值与理论值之差仅为2°。这不仅证实了理论模型的正确性，同时也证实了该观测的可靠性。

英文摘要：

Using observations of the YRY-2 borehole shear strainmeter, we studied maximum shear strain orientation of the earth＇s torsional oscillation excited by two Sumatra earthquake occurred on December 26,2004 and March 28,2005. Firstly, we did in-situ calibration for the data of borehole shear strainmeter and then detected the torsional oscillations. It is found that fundamental torsional modes 0T11～0T18 were very obvious and variation trend of the two earthquakes＇ amplitude were in agreement with each others, and variations of maximum shear strain orientations with time of fundamental torsional modes 0T11～0T18 of the two Sumatra earthquakes are small. Through the comparison, we found that the D-value of the mean measured value with theoretical anticipation value was only 2°. On the one hand, it comfirmed the theoretical model, on the other hand it also comfirmed that this observation was reliable.