Numerical Analysis of the Impact of a Pulse Seismic Source on Near-Surface Soils

Abstract

Computational technology is developed for numerical simulation of waves arising in deformable media with various rheological properties. A model of a plane-layered geological medium with homogeneous isotropic layers is proposed, which allows us to consider a two-dimensional axisymmetric problem. The numerical algorithm is based on the method of two-cyclic splitting with respect to spatial variables and physical processes. The rheological properties of materials are described by the generalized standard linear solid model (GSLS). This model is suitable for media where quality factor of oscillations is close to constant value in a wide range of frequencies, which is typical for soils and rocks. The parallel software complex for multiprocessor computer systems of cluster architecture is developed taking into account features of GSLS model. Wave fields generated by the pulse seismic source in the near-surface soils under various operation modes are analyzed. The mechanical impact of a seismic source can be considered as a two-stage process: at the first stage, elastic energy accumulates under the platform and a stress-strain state close to static is formed, and at the second stage, an instantaneous pressure release occurs with formation of a system of waves due to pulsating motions of the disturbed domain. The influence of parameters such as the radius of the platform and the duration of the pulse action on the properties of seismic waves is estimated. It turned out that varying of these parameters significantly affects the quality of the seismic signal.