| Abstract |
In Germany and other countries worldwide, the risk of seismicity induced in deep geothermal fields is seriously considered. It becomes current practice to implement local seismic networks to monitor the geothermal operations of enhanced and also hydrothermal systems. Within such context, the quantification of the capability of a network to detect a seismic event of predefined magnitude in the target zone is crucial. Here, we describe a method to estimate the sensitivity of networks deployed in areas where no natural or induced seismicity occurred in the zone of interest yet. The method is based on the calibration, for the existing network, of an amplitudemagnitude- distance relationship using the recorded regional seismicity. Applied to a detection procedure involving the signal amplitude and after extrapolation to short distances, it is possible to quantify the probability of detecting an event local magnitude at a given location. We apply this procedure on the seismic network deployed in Bruchsal (Germany) hydrothermal field. Since monitoring started, mid- 2010, no induced seismicity was identified in the area despite the good working order of the system. Hence, the question of the a priori detection capability of the network was raised. According to our approach and the applied detection procedure, there is 95% probability that no seismic event with ML. 0.7 was induced below the network footprint, at 2.5 km depth, which corresponds to the geothermal reservoir level. |