[S-SS06] New trends in data acquisition, analysis and interpretation of seismicity

[SSS06-08] Shallow rupture processes accompanying uplift at Campi Flegrei, Italy, revealed by moment tensor inversion and waveform clustering

*Giacomo Rapagnani^1,2, Simone Cesca³, Gilberto Saccorotti², Gesa Petersen³, Francesca Bianco⁴, Francesco Grigoli^1,2 (1.Earth Science Department, University of Pisa, Italy, 2.Istituto Nazionale di Geofisica e Vulcanologia, section of Pisa, Italy, 3.GFZ, Helmholtz Centre for Geosciences, Germany, 4.Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Italy)

Keywords:Seismology, Moment Tensor, Clustering, Campi Flegrei

Campi Flegrei (CF) is a volcanic system located in a densely populated area west of Naples, Southern Italy. With a long history of eruptions, CF is the largest active caldera system in Europe. The most prominent feature of CF activity is ground deformation (so-called ‘bradyseism’), which consists of rapid uplift usually accompanied by seismicity, followed by slow subsidence aseismic phases. The most recent awakening episode started almost 20 years ago, climaxing by mid 2024 with more than 1500 events/month, and largest magnitude Md = 4.4. In this work we analyze the seismic catalogue from the INGV-Osservatorio Vesuviano, from 2014 to early 2025. For a selected subset of ~110 events with Md > 2.5, we perform time-domain, full-waveform Moment Tensor (MT) inversion using data recorded by up to 40 stations within 120 km epicentral range. The inversion is conducted using a probabilistic approach. Different velocity models and frequency bands are adopted for stations located within several distance intervals. We obtain full, deviatoric and double-couple MT solutions for more than 80 events. From waveform similarity we identify 7 earthquake clusters, each characterized by similar locations and focal mechanisms. Most mechanisms indicate normal faulting; offshore events have locations and fault plane orientations which resemble the geometry of the caldera rim, while those in the most active Solfatara region mostly strike WSW-ENE. These results reveal with unprecedented detail the geometry and kinematics of the active fault structures in the Campi Flegrei region, and their relationships with volcano-tectonic lineaments.