Seismicity resulting from anthropic activity recorded in the INGV Italian Seismic Bulletin

Abstract

Quarry mining activity is intense in Italy. It produces low magnitude events recorded by the Italian National Seismic Network operated by INGV. Therefore, the Italian Seismic Bulletin (BSI) includes both tectonic earthquakes and quarry explosion recordings. Accurate seismic monitoring and analysis allow us to distinguish between anthropic and tectonic seismicity. We have analyzed data from the BSI in the period 2005-2011 using the ZMAP software (by S. Wiemer) that spatially maps out areas with an anomalous ratio of daytime to nighttime events. We pinpointed 16 areas characterized by intense extractive activities. However the number of quarries in Italy is so large that our list cannot be considered by any means complete. Extraction areas frequently coincide with regions affected by high seismicity rate. Recordings of explosion quakes can have distinctive characteristics (i.e. compressive first onset and low frequency secondary phase). Nonetheless these markers are not typical of all artificial events and are not enough to exclude all explosion recordings from the bulletin. At present, along with true tectonic earthquakes, the BSI includes a significant number of low magnitude quarry blasts, ranging between 3% and 9% per year.