Transitioning from Deterministic Active Fault Maps to Probabilistic Models for Seismic Hazard Assessment: A Global Review and the Bursa-Eskişehir Fault System (Türkiye) Case Study

Active fault maps provide the geometric backbone for probabilistic seismic hazard assessment (PSHA) and surface-fault-rupture considerations, yet what qualifies as an “active fault” varies markedly among countries and use-cases. Here we compile and compare 35 widely used mapping protocols and databases, evaluate current practice in Türkiye, and propose a harmonization framework that (i) makes the selected time window and classification logic explicit and (ii) encodes evidence quality and geometric/segmentation uncertainty in a traceable way. As a case study we apply the workflow to the multi-segment Bursa–Eskişehir Fault System (BEFS) and calculate a segment-based Cycle Ratio, CR = elapsed time since the most recent event / median recurrence interval, as a relative indicator of seismic-cycle position. In BEFS, CR spans from very low values (e.g., the Bursa segment, ~0.08) to values near or above unity (e.g., the İnegöl West segment, ~1.07), highlighting strong along-strike variability in inferred stress accumulation. We emphasize that CR is not an earthquake-timing forecast; rather, it provides an auditable prioritization layer that can be combined with slip rate, segmentation uncertainty, and event-history constraints when building time-dependent source models. The proposed workflow offers a reproducible path for incorporating Türkiye’s rapidly growing paleoseismological record into next-generation seismogenic source databases.