Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts, Azerbaijan

• Published in: Tectonics (Washington, D.C.) D.C.), 2024-03, Vol.43 (3), p.n/a
• Main Authors: Pierce, Ian, Guliyev, Ibrahim, Yetirmishli, Gurban, Muradov, Rauf, Kazimova, Sabina, Javanshir, Rashid, Pascale, Gregory P., Johnson, Ben, Marshall, Neill, Walker, Richard, Wordsworth, Paul
• Format: Article
• Language: English
• Subjects: Carbon 14; Caucasus; earthquake; Earthquake damage; Earthquakes; Fault scarps; faulting; Geologic mapping; historical earthquakes; Holocene; Mapping; Mountains; neotectonics; Plate boundaries; Plate motion; Plates; Quaternary; Radiocarbon dating; Seismic activity; Subduction; Terraces; Trenching
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2023TC007758

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. Plain Language Summary The Greater Caucasus Mountains stretching between the Black and Caspian Seas are a result of the northward subduction of the Arabian plate beneath Eurasia. For the last 1.5 million years, most of this plate motion has been accommodated by the Kura fold‐thrust belt in Azerbaijan & eastern Georgia. This plate motion produces infrequent but damaging large earthquakes. Here a geologic mapping and paleoseismic trenching investigation revealed evidence for large earthquakes in the eastern part of the Kura fold‐thrust belt of Azerbaijan. These earthquakes likely correspond to known historical earthquakes in 1668 and 1902, as well as one or more earlier, undocumented earthquakes. A lack of historical earthquakes to the west of this study area suggest that the rest of the Kura fold‐thrust belt may produce less frequent, but stronger ear