RMT and TEM Measurements on an Active Faultin Northern Greece

摘要

To improve the seismic wave propagation model it is vital to know about site effects, e.g. the geotectonic properties of the area such as the top-of-basement, vertical tectonic boundaries (faults and basement fracturation) and the geothermal regime. Therefore, we carried out near surface EM (Electromagnetic) studies to understand the distribution of the active faulting and the top of basement structure of this particular area. The RMT (Radiomagnetotelluric) and TEM (Transient electromagnetic) measurements were carried out on eight profiles, 440 RMT and 104 TEM soundings were realized. The inverted RMT and TEM data show generally a four layer model. The layers are indicated as metamorphic and sediment rocks, which are in detail: marly silty sand with gravel ( 100 Ωm), marly silty sand with clay (50 - 100 Ωm), sandy clay (30 – 50 Ωm) and silty sand (10 - 30 Ωm) with varying thickness. Due to the high resistivity of the top layer, the skin depths of the RMT soundings are around 35 m. The TEM data gives detail information of the lower structure down to a depth of 200 m. According to our analysis, a normal fault next to the Euroseistest could be located having a strike direction of N 60 E. The joint interpretation of RMT and TEM data proves to be an effective tool to investigate complex geology structures.