| Popis: |
Finding the effect of a structure with known parameters such as geometry, velocity and density underground can be defined as modelling. The purpose of the modelling is to determine the complex in-ground structure. For this, artificial seismogram models are made. Most commonly, methods based on the numerical solution of wave equations are used. Because in these methods, the source can be placed at any point of the geometry studied and instantaneous energy emanations (snap-shots) can be taken at the desired time, showing how the wave field moves on the ground. This study, it is aimed to examine the effect of boundary conditions in wave modelling with the finite difference method. For this purpose, two-dimensional scalar wave equations are modelled with the finite difference method (FDM) in the light of previously known theoretical knowledge, and how the wave field behaves in the medium using different boundary conditions is mathematically investigated. In the numerical solutions obtained with the program codes written in FORTRAN, Dirichlet and absorbing boundary conditions were used separately, and the effect of boundary conditions was revealed as snap-shot and artificial seismograms with the help of GRAPHER and MATLAB programs. From the findings, the response of the structures with smooth and simple geometry was determined with the help of seismograms and snapshots. First arrivals, reflections from the free surface, interfaces, edges and changes in energy can be observed well in the seismograms obtained as a result of the modelling made with FDM. |
