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Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts, Azerbaijan

Ian Pierce, Neill Marshall, Richard Walker, Sabina Kazimova, & Gregory P. De Pascale

Submitted September 10, 2023, SCEC Contribution #12953, 2023 SCEC Annual Meeting Poster #084

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. Quaternary 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 between central Azerbaijan and eastern 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. The first 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. A second trench approximately 60 km west of the Agsu site, was excavated near Goychay also revealing evidence of at least one surface rupturing event that occurred 334-118 BC. Although less conclusive, a second more-recent event may have occurred sometime after this first event. Holocene shortening and dip-slip rates for the Kura fold-thrust belt are ~8.0 and 8.5 mm/yr, respectively, based on the radiocarbon age of a terrestrial snail shell sampled from 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 only known historical devastating (M>~7) earthquakes in the Kura region, west of Agsu, occurred in 1139 and possibly 1668. The lack of reported historical ruptures from the past 4-8 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>7.7 earthquake.

Pierce, I., Marshall, N., Walker, R., Kazimova, S., & De Pascale, G. P. (2023, 09). Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts, Azerbaijan. Poster Presentation at 2023 SCEC Annual Meeting.

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