Том: 2020 , Год издания: 2020

Место издания: Amsterdam

We compare sensitivity of surface and shallow seismological networks in recording weak local seismic events. We analyzed real records from the existing seismological networks containing six monitoring points. Initially surface seismologic network was operated for several years. Then the seismometers were buried at the same locations to depths ranging from 70 to 90 meters. In the same region another downhole microseismic array was operating. This downhole array had the highest sensitivity providing the reference catalog of local weak microseismic events for comparison with the results of the surface and shallow seismological networks. Analysis of real-data records revealed high variability of the improvement of the station sensitivity after installing it at shallow depth. Background noise level decrease ranged from 2.5 to 40 times depending on the point. Such variability is indicating that the area is characterized by considerably different nature of background noise level. There is also significant variation in noise levels during working and non-working hours. The average noise reduction for the entire network was 11 times. Comparison with the reference catalog (from downhole array) revealed that the network sensitivity increased by 0.92 (ML) and the number of recorded weak earthquakes increased by 10 times after shallow installation.