TECTONIC LANDSLIDE ARRAYSTHE CENTRAL CAUCASUS

В статье приводятся результаты инвентаризации основных тектонических оползневых массивов Центрального Кавказа. Вначале на основе проведённого тектонического районирования выделяются основные тектонические структуры исследуемой территории. При этом в пределах данных структур приводятся данные по скорости современных тектонических движений и сейсмической активности. Площадная оценка оползневой деятельности по основным административным районам субъектов-республик, а также основным речным бассейнам, проводится с учётом результатов тектонического районирования. Дана подробная характеристика основных тектонических оползневых массивов. При этом выявлена их приуроченность к главным тектоническим структурам: выделены 3 зоны тектонических сейсмодислокаций, к которым приурочены наиболее крупные оползневые массивы исследуемой территории. The article presents the results of the inventory of major tectonic landslide slopes of the Central Caucasus. First, based on the tectonic zoning and highlights the main tectonic structures of the study area. Within these structures provides data on the speed of modern tectonic movements and seismic activity. Areal assessment of landslide activities on the main administrative districts of the constituent entities-republics, as well as the main river basin is carried out based on the results of tectonic zoning. Detailed characteristics of major tectonic landslide slopes. At the same time revealed their location to the main tectonic structures: there are 3 zones of tectonic seismic dislocation which dedicated the largest landslide arrays of the study area.

A Result regarding the Seismic Dislocations in Microstretch Thermoelastic Bodies

The aim of our study is to derive a relation of De Hoop-Knopoff type for displacement fields within context of thermoelastic microstretch bodies. Then, as a consequence, an explicit expression of the body loadings equivalent to a seismic dislocation is obtained. The results are extensions of those from the classical theory of elastic bodies.

Seismic Waves in a Laterally Inhomogeneous Layered Medium, Part I: Theory

Seismic waves in a layered half-space with lateral inhomogeneities, generated by a buried seismic dislocation source, are investigated in these two consecutive papers. In the first paper, the problem is formulated and a corresponding approach to solve the problem is provided. Specifically, the elastic parameters in the laterally inhomogeneous layer, such as P and S wave speeds and density, are separated by the mean and the deviation parts. The mean part is constant while the deviation part, which is much smaller compared to the mean part, is a function of lateral coordinates. Using the first-order perturbation approach, it is shown that the total wave field may be obtained as a superposition of the mean wave field and the scattered wave field. The mean wave field is obtainable as a response solution for a perfectly layered half-space (without lateral inhomogeneities) subjected to a buried seismic dislocation source. The scattered wave field is obtained as a response solution for the same layered half-space as used in the mean wave field, but is subjected to the equivalent fictitious distributed body forces that mathematically replace the lateral inhomogeneities. These fictitious body forces have the same effects as the existence of lateral inhomogeneities and can be evaluated as a function of the inhomogeneity parameters and the mean wave fleld. The explicit expressions for the responses in both the mean and the scattered wave fields are derived with the aid of the integral transform approach and wave propagation analysis.

Seismic Waves in a Laterally Inhomogeneous Layered Medium, Part II: Analysis

Seismic wave scattering representation for the layered half-space with lateral inhomogeneities subjected to a seismic dislocation source has been formulated in the companion paper with the use of first-order perturbation (Born-type approximation) technique. The total wave field is obtained as a superposition of the mean and the scattered wave fields, which are generated, respectively, by a series of double couples of body forces equivalent to the seismic dislocation source and by fictitious body forces equivalent to the existence of the lateral inhomogeneities in the layered half-space. The responses in both the mean and the scattered wave fields are found with the aid of an integral transform technique and wave propagation analysis. The characteristics of the scattered waves and their effects on the mean waves or corresponding induced ground and/or underground mean responses are investigated in this paper. In particular, coupling phenomena between P-SV and SH waves and wave number shifting effects between the mean and the scattered wave responses are presented in detail. With the lateral inhomogeneities being assumed as a homogeneous random field, a qualitative analysis is provided for estimating the effects of the lateral inhomogeneities on the ground motion, which is related to a fundamental issue: whether a real earth medium can or cannot be approximately considered as a laterally homogeneous layer. The effects of the lateral inhomogeneities on the ground motion time history are also presented as a quantitative analysis. Finally, a numerical example is carried out for illustration purposes.

Radiation patterns of body waves due to the seismic dislocation occurring in an anisotropic source medium

abstract We investigate body force equivalents for a seismic dislocation occurring in an anisotropic source medium and study radiation patterns of seismic body waves resulting from them. The point source representation of the equivalent body forces is obtained following a result of Kosevich (1962, 1965). Green's tensor for an anisotropic medium is calculated using a far-field approximate method by Kosevich and Natsik (1964). Radiation patterns of seismic body waves are obtained by a straightforward convolution operation on the equivalent forces with the approximate Green's tensor. The seismic dislocation occurring in an anisotropic source medium is equivalent in general to the sum of three orthogonal dipole forces with different magnitudes, for which the seismic moment tensor has a nonzero trace. Because of the third dipole force which never appears for an isotropic medium, a significant distortion of the radiation patterns occurs in a direction near the null vector. Nodal lines of P-wave radiation patterns are separated into isolated loops and/or secondary nodal lines appear. In directions where group velocity differs from the corresponding phase velocity, the effect of the medium transfer response on the polarities of body waves seems to be larger than that in other directions. The combination of the effects of source forces and medium transfer response distorts the radiation pattern.