Taking the observation data of Zhangzhou station, Fujian as an example, we determined direction of the additional strain field in observation area from data of multi-component borehole strain-meter. According to the characteristics of observation data, the dynamic strain field can be decomposed into the background strain field and the additional strain field. In order to study the variation characteristics of principal strain directions of the additional strain field, we used the formula of “lined borehole model” to calculate the vectors in principal strain directions.We also drew the vector trajectory diagram, and it is a clockwisely rotating ellipse. There was a phenomenon that the diagrams were more disordered and dispersed than the normal before the Ms 6.7 earthquake occurred in Gaoxiong, Taiwan, on March 4, 2010.%以福建漳州台深井观测资料为例,探讨用多分量钻孔应变仪资料推算测区附加应变场方向.依据观测资料的特征,把动态应变场分解为背景应变场和附加应变场.为了研究附加应变场主应变方向的变化特征,采用"钻孔加衬模型"公式,计算了主应变方向矢量,绘制了矢量轨迹图,结果为顺时针旋转的椭圆.在2010年3月4日台湾高雄6.7级地震前,矢量轨迹图有比正常情况更零乱、离散的现象.
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