GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 In the second work, we show that out of 19 moderate magnitude events considered, a common preparatory phase for 11 events is clearly identfed, plus other 5 events for which we can guess a preparatory phase but with diferent characteristcs from the previous ones. The later result confrms that even within the same tectonic context diferent possible actvaton behavior may exist. The duraton of the preparatory process ranges between about 16 hours and 4 days. We observe that also for the retrieved preparatory process a decrease in b, and Dc, and an increase of Mr, as found by many authors (Gulia & Wiemer, 2019; Mignan, 2011; Picozzi et al., 2023). Finally, we fnd a clear spatal correlaton (Fig. 1) between events with a preparaton phase and the locaton of injecton’s wells, suggestng an important role of fuids in the preparatory process. Fig. 1 – Maps of the M3.5 events compared to the areal well density (contour plot). The events with a preparatory phase are shown as red squares; yellow squares refer to the events with an unclear preparatory phase; the other M3.5 events as grey squares. References Bentz, S., Martnez-Garzón, P., Kwiatek, G., Dresen, G., & Bohnhof, M. (2019). Analysis of Microseismicity Framing ML ’ 2.5 Earthquakes at The Geysers Geothermal Field, California. Journal of Geophysical Research: Solid Earth, 124(8), 8823–8843. htps://doi.org/10.1029/2019JB017716