| Title | Tasks, Requirements and Design as Well as First Results of a Local Seismic and Vibration Impact Monitoring System for a Geothermal Power Plant in the Inhabited Area of Poing, Germany |
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| Authors | Thomas SCHICHT, Daniel BLUMRICH |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Seismic Monitoring, Monitoring System, Vibration Monitoring, one-station localization |
| Abstract | Since the incidents of the failed geothermal wells in Stauffen/Germany 2007 and, in some cases, accompanying seismic events around geothermal plants, German authorities are alert. Especially in southern Germany geothermal plants have a legal obligation to include the erection and operation of a seismic monitoring system in their operational plan. This seismic and vibration monitoring system has to fulfill at least two tasks: - Monitoring of occurring seismic events (how often, which strength, location, etc.) - Measuring of vibration impact on local residents and buildings (according to the DIN Norm 4150 part 3) One point of this obligation is the more or less permanent transmission of data from local seismic monitoring systems to the Bavarian earthquake services. That way the authorities have always the same database of the local monitoring system in addition to information from the regional earthquake monitoring system. Following these regulations a seismic monitoring system was erected and is being operated by K-UTEC AG Salt Technologies in the area of Poing near Munich in Germany. The first sensor was installed in the middle of December 2016. Already a week later a noticeable seismic event with a Magnitude ML=1.8 was recorded. The location of the seismic event could be estimated with only one installed seismic monitoring station using a geologic model and a particle motion analysis of the seismic body waves to obtain the angle of incidence. Compared to the results of the Bavarian earthquake services and the run-time analysis using the Bavarian regional seismic monitoring stations, the one-station localization capacity is quite good, i.e. a 500 m horizontal difference between the local and regional systems. The vibration impact on the local vibration monitoring station in about 300 m horizontal distance was less than 0,8 mm/s, which is far below the threshold of the DIN Norm 4150 part 3 (5 mm/s). Near the end of May 2017, a second seismic monitoring station was added to the local seismic monitoring system of the geothermal plant Poing. With these two stations it was possible to localize a seismic event in September 2017 with a local Magnitude of ML=2.1. In this case the particle motion was used as well to get the information of the angle of incidence for the seismic body waves. The horizontal distance of the localization difference between the Bavarian seismic monitoring system and the K-UTEC AG system was less than 300 m. For this seismic event the vibration impact on the local vibration monitoring station at about 200 m horizontal distance was less than 2 mm/s, which is also far below the threshold of the DIN Norm 4150 part 3 (5 mm/s). In this case 15 persons had reported the authorities that they felt the seismic event. In December 2017 the seismic monitoring network was supplemented with two additional permanent seismic monitoring stations and one mobile seismic monitoring station. The mobile station is used to measure the vibration impact in different buildings in the towns and villages around. However since September 2017 no other seismic event occurred in the local area of Poing. This work showcases the possibility and reliability of one- and two-station localization systems for seismic events by using state-of-the-art data analysis tools making it possible to detect and localize even small micro-seismic events even using such a small seismic monitoring system setup. |