# Improved Simplified Engineering Fault Displacement Hazard Evaluation Method for On-Fault Sites
## 5 Conclusions  
The presented research and the earlier efforts in [2; 3; 4; 5] aimed to assess the safety relevance of the fault displacement hazard due to the fault beneath the plant that is presumably reactivated during the Late Pleistocene period. Apart from the PSHA developed for the site located in an area with diffuse seismicity, the accurately mapped geometry of the fault, the seismogenic depth and a guess for the magnitude of 20 ka old the events could be accounted for the development of a case-specific hazard evaluation method. The presented research aimed to eliminate the conservativeness of the earlier method versions. The definition of the fault parameters based on the parameters of the PSHA models was already published in [5]. The new methodological elements are the screening method for the ruptures affecting the site, the calculation of the probability of intersections and the position of the initial point of the rupture as well as the length of the rupture relative to the site on-fault location. The improved engineering fault displacement hazard evaluation method represents the current state of the research, which was initiated by the Paks Nuclear Power Plant case. This method allows for a realistic estimation of hazard levels ranging from \(10^{-4}\)/a to \(10^{-7}\)/a, which are crucial for ensuring the safety of the nuclear power plant. The research related to the fault displacement hazard issue for the Paks site was satisfactorily resolved and completed. However, it will continue in several directions. The assurance regarding the negligibility of the fault displacement hazard at the Paks site could be increased in the future, considering the latest research effort in evaluating the paleoseismic manifestations of fault activity, e.g., [40; 41; 42; 43], especially the results of assessing source parameters and neotectonic implications in low-to-moderate seismicity regions, as seen in [44]. These aspects of the fault displacement issue have not been considered in the recent paper, but they could be part of the following safety review of the Paks NPP. The validation of the proposed methodology and all other fault displacement hazard evaluation methods depends on the accumulation of empirical evidence. The databases of observations and data evaluation achievements have great importance, e.g., [45]. Progress in developing methodologies for evaluating the fragility of nuclear power plant structures and other critical infrastructure should be considered in the future, e.g., [46]. The thorough methodology validation and investigation of methods for considering the site's soft soil conditions in the surface displacement hazard evaluation are direct continuations of the research presented in the paper. It should be acknowledged that the proposed improved fault displacement hazard evaluation is simple and conservative but not universal. Nevertheless, its use could be beneficial in many cases. The proposed simple conservative method's value can be demonstrated by considering simplicity, engineering and urgency. The preference for simplified and conservative engineering methods is always based on the time factor and sometimes on the expenses. However, it is important to note that these methods can often lead to significant cost savings in the long run. Decision-making regarding the safety and operation of hazardous facilities is complex, and engineers are contributing to the decision; their ethical imperative is to provide a solid technical basis for the decisions in the shortest time possible. In the case of the Fukushima Dai-ichi plant, TEPCO's delay in enforcing the tsunami embankment with the excuse of performing a more sophisticated tsunami hazard evaluation led to tragic consequences [47]. A safety improvement based on a simple conservative guess would cost much less than the whole plant's loss, not to mention the losses to the entire Japanese nuclear industry, the affected population and the economy. Urgency is a practical issue.