Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts, Azerbaijan

Here we present the results of the first paleoseismic study of the Kura fold-thrust belt in Azerbaijan based on field mapping, fault trenching, and Quaternary dating. Convergence at rates of ∼10 mm/yr between the Arabian and Eurasian Plates is largely accommodated by the Kura fold-thrust belt which stretches between central Azerbaijan and Georgia along the southern front of the Greater Caucasus (45-48°E). Although destructive historic earthquakes are known here, little is known about the active faults responsible for these earthquakes. A paleoseismic trench was excavated across a 2-m-high fault scarp near Agsu revealing evidence of two surface rupturing earthquakes. Radiocarbon dating of the faulted sediments limits the earthquake timing to AD 1713-1895 and AD 1872-2003. Allowing for uncertainties in dating, the two events likely correspond to historical destructive M ∼ 7 earthquakes near Shamakhi, Azerbaijan in AD 1668 and 1902. A second trench 60 km west of Agsu was excavated near Goychay also revealing evidence of at least one event that occurred 334-118 BC. Holocene shortening and dip-slip rates for the Kura fold-thrust belt are ∼8.0 and 8.5 mm/yr, respectively, based on an uplifted strath terrace west of Agsu. The only known historical devastating (M > ∼7) earthquakes in the Kura region, west of Shamakhi, occurred in 1139 and possibly 1668. The lack of reported historical ruptures from the past 4-8 centuries in the Kura, in contrast with the numerous recorded destructive earthquakes in Shamakhi, suggests that the Kura fold-thrust belt may have accumulated sufficient strain to produce a M > 7.7 earthquake.