How much of a regional Coulomb stress map survives its own uncertainty? An audit with forecast-skill validation for Türkiye

Abstract. Static Coulomb stress transfer is increasingly automated over open catalogues and fault databases rather than built by hand for single events. We ask how much of such a result survives its own inputs. For Türkiye we resolve the stress imparted by 46 Mw ≥ 6 earthquakes between 1990 and 2026 onto 6,970 sub-segments of the mapped active-fault network, screening each across 25 parameter combinations. Three silent failure modes emerge. First, 44 records of the GEM Global Active Faults Database store a central rake 180° from the circular midpoint of their own bounds; all lie in two source compilations, one being the principal North Anatolian Fault strand south of Istanbul, where it reverses the stress change from −0.029 to +0.251 MPa. Second, anchoring ruptures on catalogue centroids rather than mapped traces displaces them by a median of 18.4 km; across 27 testable events this flips the sign on a median of 11.9 % of segments against 2.0 % for a rake ±15° and dip ±10° perturbation, and is the larger of the two in 20 of them. Third, sign stability rises from 74.3 % to 89.5 % between 1 and 50 kPa. A pseudo-prospective test against subsequent seismicity gives a segment-weighted AUC of 0.711 for Mw < 7 sources, but clustering leaves an effective sample of 42, one event supplies 38 % of it, an event-equal estimate gives 0.589 ± 0.112, and distance matching leaves 0.655 with an interval spanning 0.5. Screening improves the estimate by +0.016 (95 % paired bootstrap [+0.001, +0.051]; one-sided p = 0.020). The forecast evidence is suggestive rather than strong; the two input-integrity findings do not depend on it. Coulomb maps should be published with an explicit statement of which parts are interpretable.