Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

320 PATA Days 2024 commonly used in seismology, this is called “distributed faulting…. there a few, if any, records on the size and geometry of the target fractures, i.e. the fractures being reactivated by the fault…. Hence, as there is no empirical information available, SKB has been resolved to address the issue by numerical modelling.” Thus, the rockmechanics approach was adopted during the ‘stagnant period’ in development of PFDHA (2011- 2021), when only two papers had defined the method (Youngs et al., 2003; Petersen et al., 2011). M E T H O D S This study compares predicted displacements on fractures (Fälth et al., 2015) and deformation zones (Yoon and Zang, 2019), to observed DF displacements in historic reverse (Nurminen et al., 2020) and strike- slip (Petersen et al., 2011) surface ruptures. Australian ruptures were chosen as most appropriate SCR analog; ruptures traces there were not obscured by vegetation. One Canadian rupture (Ungava) had no recognizable DFs, probably due to the thick tundra. I also derived a multivariate regression equation of the style of Nurminen et al. (2020) using just the five historic Australian SCR ruptures where DF displacements were measured. R E S U LT S / D I S C U S S I O N There were several problems comparing displacements from the 3DEC scenarios to those of real historic surface ruptures. First, the 3DEC Principal fault geometries were simplified compared to historic SCR ruptures. But the target fracture geometries and discontinuity types were very well defined, based on extensive drilling and tunnelling at the site. For historic distributed ruptures the situation is reversed. We know the exact, complicated geometry of the PF and DF surface ruptures. But almost all have ruptured upward through unconsolidated deposits, so we know nothing about the DF discontinuity geometry or type in the underlying bedrock. Fig. 1: Location of the Forsmark site (red) compared to Post- Glacial fault scarps (thick black lines with letters). Scarps labeled in blue lie in forested areas and were recently discovered with lidar.