Rapid Source Constraints and Nodal-Plane-Robust Static Stress Transfer of the 24 September 2026 Mw 5.3–5.4 Şanlıurfa Earthquake, Southeastern Türkiye

Shaheen Mohammed Saleh Ahmed 

On 24 September 2026, a moderate earthquake occurred in southeastern Türkiye near the Hilvan–Karaköprü sector of Şanlıurfa Province. The U.S. Geological Survey (USGS) reported M 5.3 at 37.4736°N, 38.8612°E and 10 km depth, whereas the Disaster and Emergency Management Authority of Türkiye (AFAD) issued a rapid Mw 5.4 solution at a shallower and approximately 5.9 km displaced hypocenter. We present a rapid, reproducible first-hours source and static-stress analysis based on openly accessible waveform and station metadata. The downloaded study archive contains 32 MiniSEED waveform files, 199 SAC traces, 25 StationXML response files, and 25 station-geometry records within a 200 km acquisition radius. After response correction, P-arrival refinement, polarity quality control, and geographic deduplication, five weighted vertical-component first motions were retained. A transparent double-couple grid search yields a provisional oblique mechanism with nodal planes NP1 = 118°/66°/−50° and NP2 = 233.9°/45.6°/−145.3°. Although all five retained polarities are fit, the solution is demonstrably underconstrained: the maximum azimuth gap is 207.7° and 1,588 near-best solutions remain. Using an Okada elastic half-space, Mw 5.3 as a working moment-magnitude proxy, 3 MPa stress drop, effective friction 0.4, and a magnitude-scaled 6.36 × 3.18 km rectangular source with 0.173 m mean slip, we calculate alternative NP1 and NP2 Coulomb failure stress (ΔCFS) fields. After excluding the inner 5 km source-core region and retaining only cells where both nodal-plane scenarios exceed +0.01 MPa, two compact consensus-positive sectors emerge approximately 5–10 km west and east of the USGS epicenter. Each covers about 34 km² and reaches a conservative scenario-overlap maximum near +0.05 MPa. By contrast, modeled ΔCFS at the centers of Hilvan, Şanlıurfa, Siverek, Bozova, Kâhta, and Adıyaman is much smaller than +0.01 MPa. An early AFAD ML 2.4 aftershock plots in a negative ΔCFS area under the source-plane receiver assumption, emphasizing that static stress maps are strongly dependent on receiver-fault orientation, source geometry, and rapid-location uncertainty. The immediate scientific priority is therefore dense near-source seismic monitoring, rapid relocation, regional moment-tensor inversion, InSAR/GNSS analysis, and fault-specific receiver-plane modelling—not deterministic prediction of the next earthquake. Same-day U.S. Geological Survey Did You Feel It? (DYFI) reporting had reached 8 community responses and community intensity V, providing preliminary evidence of moderate felt shaking but insufficient sampling for a stable spatial intensity-attenuation analysis.