THE USE OF SCALE MODELS IN TECTONOPHYSICS

Abstract

The author, using the theory of physical similarity as developed in the U. S. S. R. and equations describing the development of folds and faults in rocks, theoretically proves the possibility of using scale models in tectonophysics. New instruments necessary for investigation of equivalent materials (which are necessary for conditions of similarity) have been created in the U. S. S. R. Some substances having properties meeting model-material requirements have been known for a long time. New materials with the required properties have also been created. As a result, scale models can be practically used to study tectonic deformation and fractures. The fundamental principles of the optical method of investigation of stress state of elastic and plastic transparent models are described, indicating that the scale-model method may be used for the investigation of the tectonic-stress fields in the earth's crust. Three examples demonstrate the ability of the scale-model method to help solve different geological and geophysical problems. The hypothetical physical conditions of two types of folds - longitudinal bending and longitudinal thickening - were checked. The notions about the distribution of tectonic faults formed during the growth of transversal bending anticlines were made more precise with the aid of transparent models. Transparent plastic models are used to study the ratio of the magnitude of tangential stresses in the region of earthquake foci to the velocity of the movement of the earth's crust. In elastic transparent models it is possible to see changes in the character of earthquake foci with time due to the development of tectonic faults In such models, the influence of a type of tectonic deformation and fault magnitude on the value of seismic energy generating from the earthquake focus can be studied. All these data cannot be obtained by only field investigations. Therefore, even experimental information obtained from scale models facilitates the development of geological criteria of seismicity.