GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.1 GNGTS 2024 Fig. 1 (A) Maximum observed magnitude in catalogue vs global coefficient of variation for fifty segments of seismogenic sources in New Zealand (represented by the colour) calculated using different portions of the seismic catalogue (Mw>Mc, depth < 50 km, 1985-2022), i.e., < 1%, ∼ 7%, ∼ 1/3, ∼ 2/3 and full catalogue, one of each kind, in chronological order. This situation simulates how clustering properties of seismicity change with time as the amount of recording increases. Extremely short catalogues (corresponding to few months of recordings) are almost Poissonian with low maximum magnitude, while mid-length and long catalogues showcase clustered seismicity. The behaviour of seismic activity in the latter cases seems to be long-term time invariant, i.e., the degree of global clustering increases almost linearly. Therefore, regions with higher CV fixed the size of the catalogue may be prone to larger earthquakes. (B) Maximum observed magnitude in catalogue vs local coefficient of variation. While extremely short catalogues are locally periodic, mid-length and long catalogues showcase locally-Poissonian seismicity. Only slight positive correlation is observed between maximum magnitude and the local coefficient of variation.