A state-of-the-art analysis system designed to monitor microseismicity at a local scale

Abstract

In this paper, we review the procedures involved in establishing a contemporary workflow for real-time microseismic monitoring using a local-scale seismographic network. We draw on our specific experience in monitoring potentially induced or triggered seismicity at two adjacent oil extraction sites in the Basilicata region of Southern Italy. This monitoring effort is conducted within a regulatory framework that adheres to established guidelines. However, we perceive our undertaking as generally appropriate for any local-scale seismographic network, irrespective of the specific application planned. For this reason, here we limit ourselves to discussing issues related to accurate detection, location, and quantification of microearthquakes as discrimination of their causative process is beyond the scope of this paper. We provide an overview of the tools and methodologies essential for effective monitoring, as well as the necessary approaches for assessing the reliability and accuracy of results, with the aim of offering practical guidance to those undertaking similar projects. The paper outlines the acquisition and analysis systems, including both hardware and software components, that we routinely deploy. We assessed the spatial variability of the detection threshold of the network employing an approach based on the comparison of the actual noise level recorded at the seismic stations with the theoretical spectra corresponding to the rupture models for small earthquakes. Furthermore, various tests were conducted to ascertain the significance of noise levels and hypocentral depths on the computed detection thresholds. Special attention is given to the critical issue of addressing the inherent uncertainties in the determination of hypocenters, a factor often underappreciated in such operations. While many advanced tools are available to network operators, optimal results require proper configuration and rigorous testing of these systems.