Microseismic network sensitivity in case of no seismic activity
Abstract Underground human activities, such as mining, shale gas and oil exploitation, waste-water disposal or geo-thermal plants, can cause earthquakes. These industry projects need to be monitored by local seismic networks in order to contain the risk. An ideal seismic network should have a triangulated grid, with spacing equal to the depth of the industrial activity with no associated industry noise. In many cases, stations are placed near noisy roads, factories or in a private garden, none of which are located at optimal nodes and which thus introduce great variations in the nose level. In this article, we present a work-flow to determine the sensitivity of any local network, even if there is no local event recorded. In other words: how small are the earthquakes that such seismic networks detect? This knowledge can be used as an argument for claiming an area to be seismically silent-inactive down to a certain magnitude or for evaluating the effect of an additional seismic station.A brief theory and work-flow description is followed by two real-case demonstrations from Czech Republic, Europe: first, a proof-test on a well- studied seismically active area of West Bohemia / Vogtland and second, an application to an uprising geothermal project in Litoměřice, where no seismic activity was detected in years of monitoring.