基于PS-InSAR的怀来地震台钻孔体应变异常机理研究

Exploring the anomaly mechanism of borehole strain at the Huailai seismic station based on PS-InSAR

钻孔体应变仪是地震前兆观测与研究的主要仪器,该仪器优点是基于点的观测、观测精度高和直接观测浅层地壳应力应变信息;缺点是难以获得空间连续形变信息和易受抽水等场地环境等因素干扰。PS-InSAR方法结果为空间连续形变场和时序形变量,累计形变量与地下水位变化具有一致性。为弥补钻孔体应变监测地表形变缺陷和准确分析其观测数据中的异常信息,以怀来地震台为例,基于Sentinel-1影像,使用PS-InSAR方法对研究区地表进行沉降分析并研究2020—2021年钻孔体应变观测数据拉张异常机理。结果表明:怀来地震台附近区域的形变中心位于义合堡村东侧抽水井处;区域沉降发生时间和钻孔体应变观测异常时间与义合堡村用于供热的抽水井供暖期抽水时间相同;怀来地震台钻孔体应变观测数据拉张异常机理与附近用于供热的抽水井抽水引起的地表变化机制相一致。因此,怀来地震台钻孔体应变拉张异常变化是由义合堡村用于供热的抽水井抽水引起,同时诠释了在受地下水抽水较为明显地区内,PS-InSAR在地震前兆观测仪器观测异常机理研究的应用示范作用。

As a principal instrument for observing and researching earthquake precursors,a borehole strain meter allows for point-based observation,high-accuracy observation,and the direct observation of shallow crustal stress-strain information.However,it fails to obtain information on spatial continuous deformation and is susceptible to interference by site environments such as pumping.The persistent scatterer interferometric synthetic aperture Radar(PS-InSAR)method can derive spatial continuous deformation fields and time-series deformation,with the cumulative deformation consistent with groundwater level changes.Using the PS-InSAR method,this study analyzed the land subsidence near the Huailai seismic station based on Sentinel-1 images,aiming to counteract surface deformation in the monitoring of borehole strain and to accurately analyze the anomalous information in the observational data.This study also investigated the mechanism of extension anomalies in the 2020—2021 observational data of the borehole strain.The results are as follows:The deformation center in the area near the Huailai seismic station was situated at the pumping well east of Yihebu Village.The time of the regional subsidence and that of the observed borehole strain anomalies were consistent with the pumping time of the pumping wells for heating in Yihebu Village.The extension anomalies in the borehole strain observational data of the Huailai seismic station shared consistent mechanisms with the surface changes caused by the pumping of the nearby pumping wells for heating.Therefore,the extension anomalies of borehole strain at the Huailai seismic station resulted from pumping the pumping wells for heating in Yihebu Village.This study shows that,in areas significantly affected by groundwater pumping,PS-InSAR plays a role of application demonstration in research on the anomaly mechanism through observation using observation instruments for earthquake precursors.