On torsional wave in void type porous layers between viscoelastic and piezoelectric media with parabolic irregularity

Abstract

The viscoelastic earth model is increasingly utilized by seismologists for studying surface seismic wave propagation through Earth’s porous crustal regions such as granular materials, including rock, soils, and synthetic porous bodies. The present study characterizes torsional wave propagation in an irregular void-type porous layer sandwiched between an initially stressed inhomogeneous viscoelastic layer and a piezoelectric substratum. Displacement fields for the layer and half spaces are obtained separately using a variable separable technique, whereas volume fraction and electric potential field are derived for layer and substratum, respectively using the matrix calculus approach. Dispersion relations have been derived for both electrically open and short circuit conditions and agree with standard results. Particular cases have been deduced to validate the finding of the study with literature results. Effects of change in relevant parameters such as initial stress, heterogeneities, attenuation coefficient, void parameters, piezoelectricity and dissipation factor have been analyzed on the phase velocity of the torsional wave through various plots and summarized in a tabular form for ready reference to researchers. Analysis of the present geophysical problem may be useful in characterizing torsional velocity in porous silicate rocks which are abundantly found in the transition zone between oceanic and continental crust called Conrad discontinuity. Highlights Torsional propagation in a void-type porous layer crammed between an initially stressed inhomogeneous viscoelastic layer and piezoelectric half-space has been investigated. Variable separable technique, the matrix calculus approach is used for computing the displacement fields of respective media. A comparative study has been carried out for both electrically open and short conditions. The impact of pertinent parameters including initial stress, heterogeneities, attenuation coefficient, void parameters, piezoelectricity, and dissipation factor on the phase velocity of the torsional wave has been examined.