Abstract��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.
Tang Lei,Qiu Zehua,and Kan Baoxiang. ANALYSIS OF SHEAR STRAIN ORIENTATION OF EARTH��S TORSIONAL OSCILLATION EXCITED BY TWO INDONESIA EARTHQUAKES[J]. jgg, 2008, 28(2): 56-60.
