A Comparative Analysis of the Linear Elements of the Relief and Geophysical Fields of the Bureya and Sikhote Alin Orogens

The Bureya and Sikhote Alin orogens located in the area of the northeastern Amurian plate are characterized by different levels of seismic activity. Using the geophysical data and the data from examining specific features of the relief applying the WinLESSA program, the structure of the orogens is analyzed. As a result, the dominant extension lines of rose charts, the lineaments, the densities of lineaments of the diagonal systems, and the overall lineament density have been obtained, which are indicators of tectonic fracturing of the upper crust. These data have established that both orogens are tectonically affected by external sources (Indian-Asian interaction and the impact of the Pacific Plate), while the intensity of the process has been determined to be higher in the Bureya Orogen. Tectonic fracturing in the subsurface horizons of the crust has also been found to be increased in the Bureya Orogen compared to the Sikhote Alin one. Pronounced maxima of the overall density of preferentially NE- or NW-trending lineaments localized along the orogen axial line, are typical of the first orogen, whereas in the second case, a series of less pronounced density maxima of different orientations, which are chaotically distributed over the entire orogen, have been revealed. The data inferred from the analysis of the relief, crustal thickness, and magnetic field suggest a compression regime acting in the northern Bureya Orogen and the southern Sikhote Alin Orogen, while other parts of the orogens experience an extension regime.