Archaeoseismological Study of Medieval Monuments at the Foot of Sulaiman-Too Mountain (Osh City, Fergana Valley)

Abstract

In the fall of 2022, we studied damages at the 16th-century Ravat Abdullakhan Mosque in the city of Osh in the east of the Fergana Valley using archeoseismology method. Seismic deformations related, apparently, to the strong Kokand earthquake that occurred in 1822 have been revealed: a significant horizontal displacement of the upper part of the mosque relative to the lower part, systematic tilts of the colonnades, and rotations around the vertical axis (both of individual parts of the mosque and the building as a whole). Such severe damage could have been caused by seismic oscillations with a strength of I_l = 8‒9 (according to the MSK-64 scale). The Ravat Abdullakhan Mosque was built in the 16th century on the ruins of two more ancient structures. It is possible that two seismic events of the 12th and 15th centuries led to the destruction of these buildings (the construction of the pre-Mongol period and, presumably, the Jauz Mosque mentioned in Bāburnāma). The first earthquake is likely responsible for the destruction of the bath complex from the Karakhanid era that is located next to the mosque. The sources of seismic oscillations were tectonic movements along the zones of adyr faults and folds that were located near the Ravat Abdullakhan Mosque. It is possible that the initiator of seismic damage to the mosque was Mount Sulaiman-Too, an actively growing anticlinal adyr fold; the medieval structure under study is located at the its eastern foot.