GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.3 ______ ___ GNGTS 2023 similarities between different manifestations of fault instability. Our results are interpreted on the light of a toy-model which explains spatial patterns in the correlation between tidal stress and seismic rate during the interseismic period; conversely, a to have a drop as the stress is released through aftershocks. Different scaling exponents of spatial clustering and magnitudes relationships are found for slow and fast earthquakes being the early are more clustered; furthermore, they showcase long-lasting memory of past magnitudes. On the other hand, regular earthquakes are featured by faster decaying of memory after the mainshock, while swift, exponential drop occurs after small to moderate events. This implies that earthquakes are likely to be triggered at the edge of episodic tremor and slip regions and not far away from them, on the contrary, tremors can be triggered remotely. Moreover, energy nucleation rates become more and more correlated with tidal stress before major failures. Our results are compatible with previous literature (e.g., Tanaka 2012). At last, the responsiveness of seismicity to additional stress sources is negatively related to the temporal and spatial variation coefficients, so that the most elevated responsiveness to tidal stress is found in partially locked fault regions regularly alternating stable phases to diffuse seismic activity. Since tidal stress estimation is affected by large uncertainties, it is not reliable to define risk levels and only remote hope exists that error bars can be significantly reduced. Therefore, our approach cannot be of practical use for seismic hazard; nevertheless, it may be useful to better understand the role of slow hidden processes involving regular, slow events and tectonic tremor in the destabilisation of crust volumes.