[S02-P] Poster

[S02-P-15] The features of deep seismic structure of the area of junction of the Eurasian, Okhotsk and North American plates in Eastern Russia

^○Victor Seleznev^{1, 2}, Aleksei Liseikin², Victor Solovyev³, Aleksandr Salnikov⁴, Sergey Shibaev⁵ (1.Geophysical Survey of the Russian Academy of Sciences, Obninsk, Russia, 2.Seismological Branch of Geophysical Survey of the Russian Academy of Sciences, Novosibirsk, Russia, 3.Altai—Sayan Branch of Geophysical Survey of the Russian Academy of Sciences, Novosibirsk, Russia, 4.Siberian Research Institute of Geology, Geophysics and Mineral Raw Materials, Novosibirsk, Russia, 5.Yakutian Branch of Geophysical Survey of the Russian Academy of Sciences, Novosibirsk, Russsia)

We compared the results of seismological studies and DSS with the known geodynamic reconstructions in the area of junction of the Eurasian, Okhotsk and North American plates. Comprehensive analysis of the materials of DSS and seismology represents a significant manifestation of this area of triple junction of the plates in the deep structures of the Earth's crust and in the Moho. Abnormal of seismicity and deep structure of the zone in the alignment of the profile of the DSS is a few hundred kilometers. In the seismic section it is marked by thin (37–42 km) crust (compared with the depths to the boundary M (57 km) in the adjacent northwestern area), low boundary velocities along the Moho (7.85 to 8.0 km/s), and low average (effective) velocities of P waves in the Earth's crust (~6.3 km/s). In the plate junction area, the waves refracted from the Moho are weakly expressed in the wavefields. In the deep seismotomographic profile, this zone is marked by an extremely inhomogeneous medium crust and less contrasting reflections in the lower crust and Moho section (from the CDP data). In the wide plate junction area we have established low ratios of the velocities of P and S waves in the Earth's crust (≤1.6–1.7) and low Poisson's ratio (≤0.20), which might indicate a strong fragmentation of the crust. Position the main border between the Eurasian and Okhotsk plates specified, it passes approximately along the 144 meridian. This is confirmed by most of seismological and DSS data: the maximum number of earthquakes, maximum total released energy, major earthquakes, minimum depth of the hypocenters, local rise of the Moho and intracrustal boundary, lowest P-wave velocities in the crust, and low velocities along the boundary M. A joint border of Okhotsk and the North American plates that run along the fault Ulakhan is also contrasting on the seismic structure.