Underestimated Seismic Hazard of the Ferghana Depression: New Archeoseismological Data

The results of archeoseismological investigations carried out for the first time at the Eylatan and Kuyul’tepe ancient settlements in the Ferghana Valley (Namangan oblast of Uzbekistan) are presented. Both settlements have traces of strong seismic effects. In Eylatan there is a systematic 4-m left-lateral displacement of sublongitudinal walls along a sublatitudinal seismogenic fault. In Kuyul’tepe, numerous ruptures and fissures have been revealed in an archeological trench. Eylatan was apparently destroyed in the 1st century BC by a strong (MS = 7.6, I0 = X) earthquake, whose seismogenic rupture reached the surface in the area of this settlement. After this seismic event, people have left the ancient city and to build comparatively small settlements around it. However, another strong earthquake (I = VIII–IX in Kuyul’tepe) in the beginning of 1st millennium AD destroyed these settlements, too. The data can be used for a new seismic hazard assessment of the Ferghana depression.