GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 DISCUSSION AND CONCLUSIONS First-order observations from distance-frequency distribution of DRs are: i) there is a clear asymmetric distribution of DRs, with ruptures mostly located in the hanging wall (HW) of the PF, for both normal and reverse earthquakes; ii) in the near-fault, the hazard from distributed faulting is higher, mostly from simple DRs (rank 2); iii) the occurrence of DRs attenuates with distance. The attenuation is faster in the FW. If simple and complex DRs are considered separately, one can observe that the attenuation is mostly driven by simple DRs. The attenuation of complex DRs is less evident. Probably because complex distributed faulting occurs only if there is a pre-existing structure prone to be reactivated, while simple DRs are more related to the faulting process operating on the PF; iv) DRs for normal and reverse events have a similar distribution, but the far-fault seems to be shorter for reverse events (~20 km for normal and 7-8 km for reverse). Is this due to the difference in the mechanics of the process, or to completeness issues, or to a combination of both? v) higher magnitude events have a larger number of DRs, and distributed faulting attenuates at longer distances, as expected. First-order observations from the analysis of displacement on DRs are: i) there is a positive relation of the throw on DRs with magnitude, as expected, for all the ranking types; ii) throw on DRs attenuates with distance. The attenuation is more evident for rank 2 DRs, particularly for normal faults; iii) the relations between DR throw and PF throw are different for simple and complex DRs. Simple DRs throws are mostly below the 1:1 line (throw DR < throw PF), and there is a positive relation with PF throw. This suggests that displacement on DRs depends on and is systematically smaller than displacement on PF (correlated secondary process). Instead, several complex DRs points lye above the 1:1 line (throw complex DR > throw PF), particularly for reverse events, and the relation between displacement on DR and displacement on PF is not obvious. Strain partitioning could be a possible controlling factor. Acknowledgements This work was possible thanks to the agreement between University of Chieti – Pescara (Resp.: P. Boncio) and IRSN (Resp.: S. Baize), with which the Ph.D. project of F. Nurminen was funded.