EARTHQUAKE SWARMS AS EVIDENCE OF VOLCANO-TECTONIC PROCESSES OF THE SLOWEST SPREADING GAKKEL RIDGE IN THE ARCTIC

Abstract

Based on the data from the Arctic regional seismic stations, the article presents the results of studying the swarm seismicity of the Gakkel Mid-Ocean Ridge, located in the Arctic Ocean. The active spreading processes of ultraslow ridges with spreading rates of less than 20 mm/yr, which include the Gakkel Ridge, are still poorly understood as compared to the MOR in the Atlantic and Pacific oceans, with spreading rates of more than 25 mm/yr. In 2012–2022, there were identified eight swarms: one within the western volcanic segment of the ridge, others – in the eastern volcanic segment. No earthquake swarms were recorded in the central amagmatic segment of the ridge; the recording therein covers primarily single earthquakes and aftershock sequences. Spatially identified swarms are confied to some volcanic centers revealed earlier from the geological and geophysical data during complex expeditions. The ridge segment at coordinates ∼85…∼93° E is characterized by the most intense manifestations of volcanic processes. The spatial distribution of swarms may also indicate potential presence of volcanic structures that have not yet been identified from the geological, geophysical and geomorphological data. In the temporal domain, there can be preliminarily distinguished a 5-year swarm activation cycle, which, however, requires additional verification over a longer time interval. The swarm seismicity of the slowest spreading Gakkel Ridge cannot be described by a simple model of volcanism and magma intrusion into a symmetrical rift; it is rather a result of a complex interaction between diking and faulting with magma transport along the faults with potentially significant seismic activities. There can probably be suggested a regular combination of the processes of volcanic activation and seismotectonic destruction, which is especially pronounced in the locations of transverse faults. The results described in this article expand our understanding of the manifestation of volcano-tectonic processes occurring within the slowest speading Gakkel Mid-Ocean Ridge.