Title of research project: Seismotectonic deformations in geodynamical process: theory and applications

Period of performance: 1995 to 1996

Principal Investigator: Dr. O. Voevoda

Total funds: US$ 7,000

Summary:

Primary objectives and scope of the project. The aim of this project is to develop the method for investigation of geodynamics of seismic regions. The method is based on determination of seismotectonic deformations caused in the Earth's surface by internal earthquake sources and on probabilistic correlation between such deformations. The specific goals of the project were as follows: -determination of the representative basis for comparison of postseismic displacements, strains and tilts in different seismic regions -investigation of correlation between seismotectonic characteristics in different seismic regions. Initially the project was supposed to cover the period of two years. During the first year we intended to determine the value of the representative correlation interval and during the second year - to apply it to the analysis of geodynamics in certain seismoactive regions. Taking into consideration that ISF supported only one year, certain corrections were introduced in the plans of project realisation.

Technique and approach. The interpretation of crust movements in seismic regions is based in most cases on solution of three-dimensional problems related to static deformations of the crust caused by interior faults. The analysis of these solutions shows that postseismic crust movements depend on the parameters of the source, structure of the crust and topography of the Earth's surface. The first and the third reasons are most influential from quasistatic point of view. The basis of this study was formed by the theoretical problem of quasistatic deformation of the Earth■s relief surface by interior seismic sources (O.Voevoda 1984; O.Voevoda and L.Volynets 1992) and speculations about seismotectonic deformations (B.Kostrov 1978, L.Nikitin, S.Yunga 1981, and others). The method of this study consisted in unification of these problems with statistical methods and numerical simulation.

The findings and implications. We have developed the method for investigation of geodynamics of seismic regions. The method is based on determination of seismo-tectonic deformations caused in the Earth's surface by internal earthquake sources and on correlation between such deformations. Seismo-tectonic deformations depend on parameters of the source, structure of the crust and topography of the Earth's surface. The dependence of postseismic displacements on topography makes difficult the comparison of seismotectonic deformations in different regions. Using the methods of continuum mechanics and the theory of probability we chose the representative basis which ensures independence of geodynamic measurements of characteristics of the Earth's surface. The existence of such basis allowed us to define seismotectonic deformations as certain measurable kinematic characteristics averaged over this representative basis. Special software for analysis of the evolution of these characteristics in space and time in different seismic regions was created.