Deployment of a Distributed Fiber Optic Sensing (DFOS) monitoring station in Munich within INSIDE project

Distributed Fiber Optic Sensing (DFOS) is an innovative sensing technique, which has recently gained interest in various fields of geophysics, in particular for near-surface measurements. With the purpose of passive seismic monitoring (in the framework of the INSIDE project, supported by the German Federal Ministry for Economic Affairs and Energy, BMWi) a DFOS measurement station has been installed in Buchenhain (Gemeinde Baierbrunn, Landkreis München). Next to the DFOS system, a Trillium Compact 120 s seismometer has also been deployed to allow further processing of the data as well as the comparison of the measurements produced by the different acquisitions technologies. DFOS involves the use of optoelectronic devices, referred to as the interrogators, which send laser pulses in an optical fiber acting as the sensor. The technique aims to observe the deformation of the fiber in time and space, thanks to the light backscattered along the fiber. Therefore, the sensing technique allows interrogating long profiles with a dense spatial sampling, which is uneasy to obtain from classic geophysical techniques. Depending on the application and using the appropriate interrogator, DFOS can lead to distributed acoustic sensing (DAS), temperature sensing (DTS) or strain sensing (DSS) with various spatial and temporal resolutions. ... mehrFor instance, DAS proved its relevance for seismic applications, but also for infrastructure monitoring, among others. The DFOS station at Buchenhain allows the combined measurement of DAS, DTS and DSS data. Two fiber optic cable with different characteristics are deployed both on the surface (along a 90-m long loop) and in a dedicated well (over 250 m), which allows recording seismic signals with different directivities at the same station. After describing the measuring station and the setup, we present the results of the first months of acquisitions, including the recording of various seismic signals with among others teleseismic and regional earthquakes, as well as a nearby Vertical Seismic Profiling campaign. The joint deployment of different measurement methods on the same site gives the opportunity to evaluate the advantages of innovative seismic monitoring methods compared to more conventional ones. It also allows to consider advanced processing approaches thanks to the joint use of different types of measurements.