Large-scale geoelectrical survey in the Eger Rift zone (W-Bohemia) at proposed PIER-ICDP fluid monitoring drill sites to image fluid-related resistivity structures

西波希米亚/沃格特兰（中欧）的西埃格裂谷区的特征是大陆岩石圈地幔中持续的地球动力学活动，这种活动发生在表面没有任何目前活跃的火山活动的情况下。除了其他地球动力学现象外，板内地震群的重复和地幔源的高CO2流量是最具特色的特征。为了更好地了解地震与流体的相互作用，我们在北京地区进行了一系列的地震观测。将在500米深的地方进行地震、流体和地球物理监测。我们提出的地电预钻研究项目集中在钻孔位置与记录的二氧化碳脱气沿着附近的断层带，这是优先进行流体观测。我们建议在四个剖面上应用电阻率层析成像，以确定计划钻孔的最大深度（~500 m）的地下电阻率分布。电阻率对低电阻率流体和流体-岩石相互作用区的存在非常敏感，这些区域被认为是导电异常。结果与联合地球物理解释和约束反演与地震调查的构造信息一起，旨在成像流体通道和CO2脱气区的供给系统，成像构造特征的主要电阻率特征，并给出钻井现场表征。电阻率模型也可以用作未来测量的参考模型，以监测流体引起的电阻率变化。

The western Eger rift area in West Bohemia/Vogtland (Central Europa) is characterized by persistent geodynamic activity in the intra-continental lithospheric mantle, that take place in absence of any presently active volcanism at the surface. Beside other geodynamic phenomena are repeated intra-plate earthquake swarms and high CO2 flow of mantle origin are the most characteristic features. In order to get a better understanding of the underlying processes especially the earthquake-fluid interactions, an array of observation drillholes of appr. 500 m depth will be placed and serve for seismological, fluid and geophysical monitoring. Our proposed geoelectrical pre drilling research project concentrates on drill holes locations with documented CO2 degassing along nearby fault zones, which are prioritized for fluid observation. We propose the application of electrical resistivity tomography on four profiles to determine the subsurface resistivity distribution down to the maximum depth of the planned drillholes (~500 m).The electrical resistivity is very sensitive to the presence to low-resistive fluids and fluid-rock interaction zones, which were suggested as conductive anomalies. Results together with joint geophysical interpretation and constraint inversion with structural information of seismic investigations aim to image fluid pathways and the feeding system of the CO2 degassing areas, to image the main resistivity characteristics of tectonic features, and to give a drill site characterization. The resistivity model can also be used as reference model for future measurements to monitor resistivity changes caused by fluids.