Geodynamic Regimes in the Laptev Sea Region According to the Latest Seismological Data

This paper reports the obtained analysis data on the focal mechanisms and general distribution of earthquake epicenters in the Laptev Sea region. The principal stress axes directions were calculated by the formal stress inversion method for four groups of event clusters with known focal mechanisms. The distributions of the earthquake epicenters and crust thickness were compared. According to the seismological data, the extension axis of the Gakkel Ridge on the Laptev Sea shelf currently continues in the vicinity of the group of extension detachments located along the eastern boundary of the Anisin, Zarya, and Belkovskii–Svyatonosskii rift chains. The more ancient extension axis located along the group of detachments marking the eastern boundary of the Ust’-Lena and Omoloi rift systems and continuing the Gakkel Ridge axis is currently much less active. It carries residual stresses near its intersection with the Khatanga–Lomonosov fault zone in the northwestern parts of the shelf area and with the Lena–Taimyr zone of boundary uplifts, in the southwestern part. The axes oriented along the Olenyok and Bykovskii channels and the Siberian Platform boundary form extension conditions in the eastern part and strike–slip conditions in the western part of the Lena delta area.