PALEOGEODYNAMICS
The analysis of the neotectonic structure of the region is usually accompanied by the compilation of neotec‐ tonic maps and schemes. Models of the summit surface serve as the initial material for compiling different‐scale neo‐ tectonic maps and schemes [Ufimtsev, 1984].
The summit surface is one of the main properties of the Earth's recent topography (including the land surface and sea bottom) and represents an ideal surface connecting the maximal heights of the present‐day relief of different geo‐ morphologic levels. The universal development of the summit surface allows in to be used for revealing and studying the neotectonic structural elements both on land and seas.
When compiling the structural – neotectonic map of the Sea of Okhotsk (Fig. 2), we accepted the polygenetic poly‐ chronous “summit” surface of the sea bottom shown by the isobaths relative to the present‐day sea level as the prima‐ ry (“structural”) one. The map is largely based on data from the bathymetric maps and represents, in fast, a static model of neotectonics. The structural‐neotectonic map served as a basis for compiling the scheme of the principal neotectonic structural elements of the studied region (Fig. 3).
For clarifying the formation history of the neotectonic structural elements, we compared their present‐day spatial position relative paleogeographical schemes of the lithophysical complexes (LC), which are united into four regional seismostratigraphic complexes (RSSC) corresponding to the following time intervals: RSSC I to K2–P1‐2; RSSC II to P3–N11; RSSC III to N11‐2; RSSC IV to N13–N2 [Sergeyev, 2006], besides showed general characteristic of the paleo‐ geographical settings that controlled the accumulation of different lithophysical complexes (Fig. 4).
TECTONOPHYSICS
Observations of earthquake migration along active fault zones [Richter, 1958; Mogi, 1968] and related theoretical concepts [Elsasser, 1969] have laid the foundation for studying the problem of slow deformation waves in the lithosphere. Despite the fact that this problem has been under study for several decades and discussed in numerous publications, convincing evidence for the existence of deformation waves is still lacking. One of the causes is that comprehensive field studies to register such waves by special tools and equipment, which require sufficient organizational and technical resources, have not been conducted yet.
The authors attempted at finding a solution to this problem by physical simulation of a major shear zone in an elastic-viscous-plastic model of the lithosphere. The experiment setup is shown in Figure 1 (A). The model material and boundary conditions were specified in accordance with the similarity criteria (described in detail in [Sherman, 1984; Sherman et al., 1991; Bornyakov et al., 2014]). The montmorillonite clay-and-water paste was placed evenly on two stamps of the installation and subject to deformation as the active stamp (1) moved relative to the passive stamp (2) at a constant speed. The upper model surface was covered with fine sand in order to get high-contrast photos. Photos of an emerging shear zone were taken every second by a Basler acA2000-50gm digital camera. Figure 1 (B) shows an optical image of a fragment of the shear zone. The photos were processed by the digital image correlation method described in [Sutton et al., 2009]. This method estimates the distribution of components of displacement vectors and strain tensors on the model surface and their evolution over time [Panteleev et al., 2014, 2015].
Strain fields and displacements recorded in the optical images of the model surface were estimated in a rectangular box (220.00×72.17 mm) shown by a dot-and-dash line in Fig. 1, A. To ensure a sufficient level of detail in the analyses of the strain fields in each optical image, the selected area was covered with a uniform mesh (3.43×3.43 mm). In the zoomed-up images, the mesh was 32×32 pixels (a pixel of 0.107×0.107 mm). For each pair of optical images, we calculated cross-correlation functions of the intensity of pixels between pairs of the same size cells (Fig. 2). Directions and magnitudes of displacements of the cells were determined from displaced maximums of cross-correlation functions (