Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts,
Azerbaijan
Abstract
Quaternary convergence at rates of ~10 mm/yr between the
Arabian and Eurasian plates is largely accommodated by the Kura
fold-thrust belt at the longitude of the Greater Caucasus Mountains in
Azerbaijan and eastern Georgia. Here we present the results of the first
paleoseismic study of the Kura fold-thrust belt in Azerbaijan. A single
paleoseismic trench was excavated across a 2-m-high fault scarp near
Agsu revealing evidence of two recent surface rupturing earthquakes.
Radiocarbon dating of the faulted sediments places limits of earthquake
timing of AD 1713-1895 and AD 1872-2003 for the two events. Allowing for
uncertainties in radiocarbon dating, the two events likely correspond to
historical destructive M~7 earthquakes near Shamakhi,
Azerbaijan in AD 1668 and 1902. Holocene shortening and dip-slip rates
for the Kura fold-thrust belt are 8 and 8.5 mm/yr, respectively, based
on the depositional age of an abandoned uplifted strath terrace in a
water gap to the west of Agsu. These rates should be treated as maxima,
as they are ~100% of the previously determined
structurally and geodetically measured shortening across the belt, and
were measured from only one of two primary structures in this part of
the belt. The lack of reported historical ruptures from the past 8
centuries to the west of Agsu, in contrast with the numerous recorded
destructive earthquakes of the Shamakhi region, suggests that the
central and western parts of the Kura fold-thrust belt produce less
frequent, but more destructive earthquakes, and may have accumulated
sufficient strain to produce a M>8 earthquake.