临汾龙祠地震台水准测量巨幅形变异常综合分析

COMPREHENSIVE ANALYSIS OF HUGE LEVELING DEFORMATION ANOMALY AT LINFEN LONGCI SEISMOSTATION

通过两轨法D-InSAR技术获取了临汾水准两次巨幅变化期间区域地壳垂直形变场,结合BM3点周围高密度电法勘探结果,分析认为:临汾水准所在的区域垂直形变场中未出现与断裂走向一致且与巨变幅度相匹配的连续形变异常区,其巨幅变化属于局部地区小范围的变形,在InSAR形变图上无法显示。BM3点建立在第四纪全新世次生黄土上,位于高密度电法勘探发现断层之东3米处,自观测以来相对于稳定的基岩点年均下降5.11 mm,是同为土层点的BM4点下降速率的4倍,且临汾水准巨幅变化前的加速变化与BM3点附近挖墓的时间较一致,可能是新坟破坏了隔水层,为农田灌溉时地表水进入深部提供了通道,其潜蚀作用使上部土体疏松而引起测点快速沉降。

The ground vertical deformation fields during the two times of huge deformation anomaly are figured out by D-InSAR technique,along with the results of high-density electric exploration around No BM3 benchmark,we drew several conclusions.Firstly,the InSAR-derived deformation fields indicate there is no continuous deformation anomaly that is related to the fault strike.In another word,the anomaly only showed in a local small area.The other fact is that the No BM3 benchmark was built on the Holocene secondary loess,with the subsidence velocity of 5.11mm/a which is four times of the No BM4.And the anomaly time is consistent with that of the tomb construction.Secondly,the anomaly at No BM3 benchmark should be related to the newly made tomb.The tomb construction may break the impermeable layer,which created a conduit between ground surface and the deepth.Thus,the No BM3 benchmark showed a rapid subsidence during the irrigation season when the subsurface erosion action made upper soil loose.