RECENT GEODYNAMICS
Natural-science concepts of rotational movements and the ‘lumpy’ structure of medium are reviewed with a focus on key aspects. Through using torsional traps for hunting and «implementing» mechanical torque for ignition, Homo sapiens developed to man. Vortex movements «impregnated» in spiral structures of shells and torsional movements of toothy whales and fish were intuitively perceived by man as major stable movements of the environment. Based on the above, the ancient philosophy established the concept of the uniform world represented by atomic («noncuttable») structure of medium and vortex movements of ether. Based on conclusive arguments stated by R. Dekart, H. Helmgolz, Lord Kelvin and others within the framework of classical physics and in the first half of the 20th century by scientists in quantum physics and cosmogony, both «quantum structure» («lumpiness») and rotation («vorticity») are integral features of matter – space – time throughout the whole range from elementary particles to galaxies and galactic clusters.
Nowadays researchers in natural sciences, particularly in the Earth sciences, call attention again to the problem of structure of matter and its movements. In the 1920s, Chinese geologist Li Siguang established fundamentals of vortex geodynamics. In the second half of the 20th century, Li Siguan’s concepts were developed by geologists O.I. Slenzak and I.V. Melekestsev. Geologist A.V. Peive, mechanic L.I. Sedov and physicist M.A. Sadovsky put forward a concept of block structure of the geo-medium (geological and geophysical medium) and proposed a justified assumption that such blocks can move by own torque. This method of movement is confirmed by results of geological and tectonophysical studies, as well as instrumental geophysical measurements obtained from a variety of stations and focal zones of strong earthquakes. Many researchers, including W. Elsasser and V.N. Nikolaevsky, develop fundamentals of nonlinear wave mechanics of the geo-medium, admitting rotational movements of blocks. According to М.V. Stovas, V.Е. Khain and other researchers, rotation of the planet around its axis is of critical importance for understating the origin of geodynamic movements.
Based on the review of results from the previous comprehensive geological and geophysical studies, a conclusion is made on the torque origin of rotating block geo-medium which is termed as Peive–Sedov–Sadovsky medium. Analyses of migration of earthquake foci and volcanic eruptions and movements of edges of tectonic plates provided grounds to design a principally new model, and this rotational model is described in the present publication. Blocks and plates interacting with each other in the model are interrelated by long-range elastic fields which comprise a uniform planetary geodynamic medium, i.e. ‘self-consistent’ state of the geo-medium. Briefly reviewed are data about vortex geological structures and rotary motions of blocks and plates; such data have been detected and recorded in abundance in a variety of geophysical fields. It is stressed that similar, in principle, vortex movements / flows are solutions of the well known Dirichlet–Dedekind–Riemann problem of rotating and gravitating liquid drop that is the problem of the Earth’s equilibrium shape. According to the proposed rotational model, geodynamic solutions of the rotational model combine geodynamic flows in the solution of the problem of the Earth’s equilibrium shape and geologic-geophysical vortex structures and movements on the Earth’s surface in one and the same class of phenomena. It is proposed to apply such solutions for establishing a new geological paradigm – new torque (and/or wave / vortex) geodynamics.
Three-dimensional space-time diagrams of «logarithm of total energy released by earthquakes» parameter, lgEsum are constructed for regions with stable concentrations of earthquake epicenters in Cis-Baikal region for a period from 1964 to 2002. Based on analyses of such diagrams, areas of slow migration of seismic activity are defined. Estimated are distances, time and velocities of slow migration in the range of the first kilometers – first dozen of kilometers per year.
Procedures of seismic data projection and construction of 3D diagrams are described in brief. A general scheme including contours of projection areas is proposed for the Pribaikalie (Fig. 1).
Three space-time diagrams are presented as examples of application of the above mentioned procedures. They are constructed for the Middle and Southern Baikal basins and the western part of the NE flank of the Baikal rift system (Fig. 2). Integrated analytical results are presented for all the diagrams which record earthquake migration within the Baikal rift system.
We also present a scheme of the zone of slow migrations ranked by dominating velocities (Fig. 3) and a diagram of the migration velocity range. We consider possible causes of slow migration of seismic activity at variable velocities: (1) slow deformation waves spreading in the crust, and (2) independent propagation of the deformation front along active faults.
Regulations of migration of strong earthquakes can be useful for definition of timelines and locations of future strong seismic events.
TECTONOPHYSICS
The publication is aimed at comparing concepts of V.V. Belousov and M.V. Gzovsky, outstanding researchers who established fundamentals of tectonophysics in Russia, specifically similarity conditions in application to tectonophysical modeling. Quotations from their publications illustrate differences in their views. In this respect, we can reckon V.V. Belousov as a «realist» as he supported «the liberal point of view» [Methods of modelling…, 1988, p. 21–22], whereas M.V. Gzovsky can be regarded as an «idealist» as he believed that similarity conditions should be mandatorily applied to ensure correctness of physical modeling of tectonic deformations and structures [Gzovsky, 1975, pp. 88 and 94].
Objectives of the present publication are (1) to be another reminder about desirability of compliance with similarity conditions in experimental tectonics; (2) to point out difficulties in ensuring such compliance; (3) to give examples which bring out the fact that similarity conditions are often met per se, i.e. automatically observed; (4) to show that modeling can be simplified in some cases without compromising quantitative estimations of parameters of structure formation.
(1) Physical modelling of tectonic deformations and structures should be conducted, if possible, in compliance with conditions of geometric and physical similarity between experimental models and corresponding natural objects. In any case, a researcher should have a clear vision of conditions applicable to each particular experiment.
(2) Application of similarity conditions is often challenging due to unavoidable difficulties caused by the following: a) Imperfection of experimental equipment and technologies (Fig. 1 to 3); b) uncertainties in estimating parameters of formation of natural structures, including main ones: structure size (Fig. 4), time of formation (Fig. 5), deformation properties of the medium wherein such structures are formed, including, first of all, viscosity (Fig. 6), ultimate strength, and tectonic stresses which caused formation of such structures (Fig. 7).
(3) A way to overcome the above mentioned difficulties can be found through awareness of the fact that physical similarity conditions are often met per se, i.e. automatically observed due to linear relationships between similarity coefficients (Fig. 8). For example, decreasing the viscosity of the equivalent material will result in corresponding decrease of time required for deformation of the given model, all other conditions being equal. Moreover, it is possible to use this similarity condition, i.e. an equation in one unknown, not only to select a required equivalent material, but also to quantitatively estimate the natural parameter in the given condition.
(4) Another way to overcome the above mentioned difficulties is simplification of modeling in cases when it is required to obtain qualitative results without any quantitative evaluations of parameters of structure formation (Figures 9 to 14). This necessitates development of fundamentally new criteria of similarity for modelling. For instance, it can be absence or presence of the original (pre-deformational) structuring of the geological medium that is preconditioned by previous deformation processes of self-organization of the givem medium. Possibilities of simulation of the selforganization shall be the subject of our future study. It is also needed to elaborate new similarity criteria for modeling of hierarchically subordinate geodynamic systems and structural parageneses. So far it has been accepted that simulations of the kind should be conducted on the principle of selectivity (separate simulation), established by M.V. Gzovsky [1975], such as, for example, separate simulation of folding and cleavage.
Having his own experience of 40+ years in experimental tectonics, the author addresses his views to young researchers, who are apprehensive about the need to ensure compliance with similarity conditions in physical modeling of tectonic deformations and structures, and to those members of editorial boards and reviewers of scientific journals who believe that authors should mandatorily declare such compliance. As a result, it is not uncommon that, striving to declare that this requirement is observed, an author saturates his/her papers with complicated equations which do not reflect the actual compliance with similarity conditions and thus become a mere demonstration of the author’s erudition in mathematics.