Seismic refraction modeling using finite difference method and its implications in the understanding of the first arrivals

Abstract

This paper presents the results of the seismic refraction modeling using finite differences method (FDM), implemented in the program from the open source package Seismic Unix (SUFDMOD2), and its comparison with the modeling by time-term method (TTM) from the SEISIMAGER© software. The applied velocity model corresponds to the typical measurements situation in a seismic refraction survey. The depth of refraction interfaces varies approximately from 2 to 6 meters, thus allowing examining the propagation of head waves with the variable dip angles. The synthetic seis-mograms allow us identifying the first arrivals of head waves, which are subsequently the travel-time curves. The analysis of results obtained with FDM and TTM algorithms shows a high correlation with the refraction arrival times, but a low correlation with the arrival times of the direct wave. Finally, the obtained results allow concluding that the seismic modeling of the propagation of head waves using the method of finite differences makes it possible to accurately determine the first arrival time within the complex geological conditions and the velocity dispersion between the layers. The goal of this work is to show how these findings can be applied to seismic modeling by the method of finite differences for calculation of the first arrival time and clarify the results of measurements conducted in real conditions.