GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 Italian earthquake sequences under the microscope P. Poli 1 , L. Cabrera 2 , D. Essing 2 1 Dipartimento di Geoscienze, Università di Padova 2 ISTerre, University of Grenoble The recent advancements in seismological data analysis, permit to rapidly parse long time series of data, and to improve the detection of small, but abundant earthquakes. Among these techniques, template matching utilizes the waveforms of known earthquakes (e.g. the Iside seismic catalog), to discover new ones by means of array coherence. The techniques can improve the number of detected events by a factor of 10 to 20, permitting the detection of a large number of smaller earthquakes, down to negative magnitude. The technique is not without caveats, and it is often used as a black box. The lack of knowledge and testing of parameters, can provide catalogs with rich false detections, or incomplete observations (e.g. missing many earthquakes). In this contribution we first discuss how to parametrize template matching studies while maximizing the detection power and reducing false detections. To that scope, the choice of appropriate data processing, optimal frequency band, and high quality templates will be discussed, along with strategies to test the incidence of false detections. We will then present some catalogs made by template matching using data from the Italian seismological network. The first catalog is made using data from the near fault observatory in the Alto Tiberina region, contains up to 500k events, during 3 years, and events with magnitude down to -2. This new catalog is compared with other template matching catalogs for the same region, to discuss the importance of properly setting up the detection problem. We then show the importance of detecting so many small magnitude events to reveal the detailed spatio-temporal evolution of the seismicity, which reveal fundamental insights about the dynamics of the seismicity. We will further introduce a new catalog for the central Apennines, covering the period 2009-2017. We again compare the results with previous compilations, illustrating the importance of working with homogenous data, and with proper frequency bands. We will then discuss the properties of the seismicity for this high-resolution catalog, which include the most important seismic sequences in Italy, for the last 20 years. Corresponding Author: P. Poli email: piero.poli@unipd.it