SEISMODYNAMICS AND DEEP INTERNAL ORIGIN OF THE NORTH CHINA ZONE OF STRONG EARTHQUAKES

• Published in: Geodynamics & Tectonophysics
• Main Author: Andrey A. Stepashko
• Format: Article in Journal/Newspaper
• Language: English; Russian
• Published: Russian Academy of Sciences, Siberian Branch, Institute of the Earth's crust 2015
• Subjects: north china seismic zone; sino-korean craton; tan-lu fault zone; lithospheric structure; deformation wave; seismic cycles; earthquake migration; Science; Q; Pacific; Sakhalin
• Online Access: https://doi.org/10.5800/GT-2011-2-4-0049; https://doaj.org/article/c17e891d1450470b82ced055f6cebe62

Space-and-time regularities of seismicity of the North China (Tan-Lu) zone are studies, and tectonic nature of strong earthquakes is analyzed. The concept of its genesis is still a matter of debate as this zone is located in the centre of the ancient SinoKorean craton, i.e. thousand kilometers away from convergent margins of Eurasia and the Pacific оcean and IndoAustralian plates (Figure 1). The information on the regional cycling dynamics [Xu, Deng, 1996] is updated. Two cycles, in which strong earthquakes (14 shocks with М≥7.0) occurred in the region under study, are distinguished, i.e. from 1500 to 1700, and from 1800 to 1980 (Figure 2). The seismodynamics of the North China zone is consistent with the Circum Pacific оcean deformation wave that occurs once in 300 years at the margin between Asia and the ocean and thus causes the strongest earthquakes (М≥8.8) and eruptions of volcanoes in the Pacific оcean belt [Vikulin et al., 2009, 2010]. This wave came to the northern regions of China in the years of 1500 and 1800 (Figure 3) and triggered seismic activity cycles. The second factor predetermining the seismicity of the Northern China is a specific structure of the region which can manifest seismic activity due to the impact of deformation waves. The genesis of the metastable structure of the region is related to tectonic restructuring of the lithosphere of the SinoKorean craton due to shear displacements in the Tan-Lu megazone. Regional variations of compositions of mantle xenoliths of the Sikhote Alin orogeny demonstrate that the latent strike of the Tan-Lu faults can be traced across the south-eastern areas of Russia to the Tatar Strait. These faults are borders of the Vshaped mantle block (400 x 1500 km) (Figure 5), which composition is characterized by an anomalous content of iron and a low depletion of peridotites. The tectonic mantle block maintains its activity; being impacted by compression from the west, it is squeezed out towards the Sakhalin Island and simultaneously subject to the clockwise ...