1,000-km distant dynamic triggering of large aseismic fault slip and mud volcano unrest in the Eastern Caucasus

Dynamic triggering of local seismicity or slow-slip events by large earthquakes over vast distances is a well-documented phenomenon. Using satellite radar interferometry (InSAR) and seismic data, we identified a significant  aseismic deformation signal in the Eastern Kura Basin, situated between the Lesser and Greater Caucasus thrust belts, at the diffuse boundary of the converging Eurasian and Arabian plates. This deformation is concentrated along the 170-km-long West Caspian Fault (WCF) and six shorter, sub-parallel faults (<70-km); it is also associated with unrest at 56 mud volcanoes over known hydrocarbon reservoirs.

Surface displacement fields from four InSAR tracks constrained the aseismic slip to a transient event between 4 and 9 February 2023, with no significant pre- or post-slip deformation. However, InSAR and GNSS  analysis over a longer time-frame indicates that the WCF and sub-parallel faults are continuously creeping. Seismic analysis of data from a station 2 km away from the WCF identified 58 high-frequency local events at depths ranging 10–20 km, with magnitudes below 3.2. These events coincided with the arrival of surface waves from the 6 February 2023, M7.8/M7.6 Kahramanmaraş earthquakes in eastern Türkiye, over 1,000 km away. SAR coherence and interferometric phase maps also revealed eruptions and deformation at 56 mud volcanoes during this period, suggesting a fluid-mediated dynamic triggering mechanism. Our inversion of displacement fields indicates right-lateral strike-slip motion along the vertical WCF and sub-parallel faults, incorporating hydrocarbon reservoir inflation.

We interpret the observed aseismic slip as a fluid-mediated transient event dynamically triggered by the surface-waves of a 1000-km distant earthquake, which altered pore pressure and normal stress on optimally oriented faults in the Eastern Kura basin. This event represents one of the largest documented aseismic crustal slips in a continental collision zone. Despite the continuous creep and transient slip behavior observed along the WCF,  its potential for generating large seismic events remains uncertain.