Local geophysical investigation in the surroundings of the new German Regional Seismic Network station Heukewalde in Thuringia, Germany

Abstract

ABSTRACTIn 2008, the Institute of Geosciences Jena installed a new seismic station about 20 km south‐east of Gera, close to Heukewalde in Thuringia, Germany. This station is embedded in the Thuringia Seismological Network (TSN) and in the German Regional Seismic Network (GRSN). The area around Heukewalde (approximately 1 km2) was investigated by local geophysical measurements. The priority objective of these studies was to answer the question about the quality of the new seismic station location regarding the geophysical and geological situation. The Bouguer anomaly shows amplitudes of 1.25 mGal (= 1.25·10‐5 m/s2) at maximum, the magnetic total intensity yields approximately 50 nT and the electromagnetic investigation shows a conductivity up to 85 mS/m. The local anomaly patterns and their interpretation are strongly correlated and in high agreement with geological information. According to this the station Heukewalde is placed directly at a north‐south striking fault zone. The area west of this zone consists of Silurian grapholite and siliceous schist, covered by drift clay. The eastern part is characterized by Rotliegend conglomerates. Additionally, Devonian titanic iron ore diabases are outcropped at the fault zone, which is also reflected by significant signatures in the anomaly fields. The resulting anomalies of the different geophysical methods and additional results of geoelectrical investigations confirm the main statements of the existing but very old geological map. Here we show that the location of the new station should be discussed critically from a seismological point of view, because the geological situation close to the station is very heterogeneous.