GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 ● Primary: these faults represent the primary surface expression of the deep seismogenic source, as such representing the main structural element controlling the Quaternary local landscape evolution. ● Secondary: these faults represent secondary synthetic or antithetic surface faults connected to the deep seismogenic source, or other faults not structurally connected to the main fault, as such comprising the so-called distributed faulting. ● Unknown: due to lack of data, the rank of these faults is simply unknown , meaning that their link with the underlying seismogenic source is still to be defined. Developments The method adopted for the association used in the current implementation of the DISS-ITHACA interoperability tool implies that each selected ACF is associated with the entirety of one or more CSSs. This procedure does not consider that the CSSs are fault systems, and that the earthquakes associated with them may rupture individual or multiple segments of each system. A consequence of this approach is that it cannot provide plausible surface faulting scenarios – either primary or distributed – for earthquakes rupturing just a segment of a long seismogenic source. To overcome this limitation, we are developing a new association method that consists in (a) segmenting each ACF in fixed length sections, and (b) identifying discrete CSS rupture segments by scaling their dimension to the maximum magnitude earthquake associated with the CSS itself; the rupture segments are then shifted along the CSS at fixed steps, so as to take into account the epistemic uncertainty arising from the variability of their position. The method then uses a conditional probability function to calculate the association of each ACF section with a specific rupture segment of each CSS, based on their mutual distance. This new approach highlights the higher or lower probability of association of each ACF section with each CSS rupture segment, and may be further improved for the construction of realistic surface faulting scenarios.