Transformations of Obliquely Striking Waves at a Rock Joint: Numerical Simulations

Knowledge of wave propagation across rock joints is necessary for understanding distinctions between wave attenuation and lithology. Whenever a propagating seismic wave strikes a rock joint at an angle not normal to the joint, wave transformation occurs. The rock joints existing in the field are not oriented in the condition for normal incidence of the wave; hence, wave transformations are very common. In this paper, transformations of P and S-v waves have been modeled numerically with the help of a distinct element method. Validation of the numerical model has been carried out by comparing the wave velocities obtained from bender/extender elements. The dependence of the transformation of obliquely striking waves on the frequency of incident waves and stiffness of the joint has been studied. The velocities of propagating waves and the ratios of stress amplitudes of propagating waves with respect to the incident wave have been obtained and compared for all the possible angles of incidence. The wave velocities and amplitudes of propagating stress waves are found to be dependent on the angle of incidence of the waves at the rock joint. It was observed that the transformed waves that are of the same type as the incident wave contain more energy. (C) 2016 American Society of Civil Engineers