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甘孜台地电阻率N30°E测道观测资料自2011年7月开始出现趋势上升变化,N60°W测道地电阻率则从2012年出现趋势上升变化。2011年测区原317国道实施扩建工程,N30°E测道测量电极分别向供电极方向移动10m。采用甘孜台电测深曲线以水平层状模型反演了测区的电性结构,理论计算表明,测量电极的移动将会引起N30°E测道4Ω·m的上升变化,扣除这部分变化后,甘孜台两测道观测值于2012年同步上升。以水平层状模型计算了甘孜台两测道各层介质的影响系数,两测道浅层两层介质影响系数均为负,能合理地解释甘孜台地电阻率在雨季降水量增加时观测值上升、旱季降水量减少时观测值下降这一“夏高冬低”的年变现象。建立三维有限元模型计算了317国道拓宽部分对观测的影响,计算结果表明,拓宽部分仅能引起N60°W测道约0.15Ω·m的下降变化和N30°E测道约0.1Ω·m的上升变化,其对观测的影响非常小。同时2013年1月甘孜台两测道年变低值显著高于2008年以来各年的年变低值,在芦山地震前呈同步的上升变化,但是与汶川地震前的下降变化相反,因此甘孜台自2012年的趋势上升变化是不是芦山地震的前兆异常还难以确定。
The observation data of the N30 ° E resistivity of Ganzi platform show an upward trend of change since July 2011, while the resistivity of the N60 ° W channel shows an upward trend from 2012 onwards. In 2011, the original State Road 317 of the surveyed area was undergoing expansion project. The measuring electrodes of N30 ° E were respectively moved 10m toward the electrode. The electrical structure of the survey area was inverted by the horizontal stratified model using the sounding curve of Ganzi. The theoretical calculation shows that the movement of the measuring electrode will cause the increase of 4Ω · m at N30 ° E. After subtracting this change, Ganzitai two observation stations in 2012 increased simultaneously. The horizontal stratified model is used to calculate the influence coefficient of each medium in two tracks of Ganzi station. The influence coefficients of the two layers of medium in the two tracks are all negative, which can reasonably explain that the observation value of the resistivity of Ganzi platform rises when the precipitation in rainy season increases , When the precipitation decreases in the dry season, the observed value of this “summer high winter low” annual change phenomenon. The three-dimensional finite element model was used to calculate the influence of the widened part of National Highway 317 on the observation. The calculation results show that the widening part can only cause the decrease of about 0.15Ω · m at the N60 ° W channel and about 0.1Ω · m at the N30 ° E channel Rising changes have little effect on the observations. At the same time, the annual change of Ganzitai 2 track in January 2013 was significantly higher than that of each year since 2008, showing a synchronous increase before the Lushan earthquake but opposite to the decline before the Wenchuan earthquake. Therefore, It is difficult to ascertain whether the rising trend of Taiwan’s trend from 2012 is an anomaly of the Lushan earthquake.