S. Stein and M. Wysession's An Introduction to Seismology, Earthquakes, and Earth Structure is the textbook I've been waiting for. It combines the pedagogical strengths of Introduction to Seismology by P. Shearer (1999) and the breadth of coverage of Modern Global Seismology by T. Lay and T. Wallace (1995). The “price” of this combination is a rather lengthy text, but it is so well written that the length can be easily forgiven.

At first glance, An Introduction to Seismology Earthquakes, and Earth Structure appears to follow a very traditional path, beginning with a nice overview chapter on the relevance of seismology, followed by chapters on seismic waves that include stress and strain basics, Earth structure, earthquake sources, and seismology and plate tectonics. On closer inspection, though, the reader will find many chapter sections that are rather novel. Included among these are waves on a string, an excellent way to introduce students to the complexity of seismic waves; earthquake geodesy which establishes the important connection between seismology and deformation studies; and plate kinematics, a clearly presented “short-course” on plate motion studies. These sections, and others like them, significantly enhance the text. The latter two in particular help give the book a broader perspective that is rare in standard seismology texts.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003EO220007

An Introduction to Seismology, Earthquakes, and Earth Structure

The present paper is concerned with the propagation of shear waves in a homogeneous viscoelastic isotropic layer lying over a semi-infinite heterogeneous viscoelastic isotropic half-space due to point source. The inhomogeneity parameters associated to rigidity, internal friction and density are assumed to be functions of depth. The dispersion equation of shear waves has been obtained using Green’s function technique. The dimensionless angular frequency has been plotted against dimensionless wave number for different values of inhomogeneity parameters. The effects of inhomogeneity have been shown in the dispersion curves. graphical user interface (GUI) software in MATLAB has been developed to show the effect of various inhomogeneity parameters on angular frequency. The topic can be of interest for geophysical applications in propagation of shear waves on the Earth’s crust.

Effect of point source and heterogeneity on the propagation of SH-Waves in a viscoelastic layer over a viscoelastic half space

The propagation of horizontally polarised shear waves in an internal irregular magnetoelastic self-reinforced stratum which is sandwiched between two semi-infinite magnetoelastic self-reinforced media is studied. Two shapes of irregularities on the interface of layer and lower semi-infinite media are considered, namely rectangular and parabolic. The dispersion equation is obtained in closed form. The combined effects of reinforcement, magnetic field and irregularity are also studied. Some important features of the results are highlighted. It is also observed that the dispersion equation is in agreement with the classical Love-type wave equation for an isotropic layer sandwiched between two isotropic half-spaces in the absence of reinforcement, magnetic field and irregularity.

Propagation of magnetoelastic shear waves in an irregular self-reinforced layer

The present paper discusses the dispersion equation for horizontally polarized shear waves (SH waves) in a non-homogeneous self-reinforced layer over a semi infinite self-reinforced medium with an irregularity. The dispersion equation has been obtained in closed form. In the isotropic case, when non homogeneity and irregularity are absent, the dispersion equation reduces to standard SH wave equation. The dispersion curves have been presented by means of graphs for different sizes of irregularity and different values of non-homogeneity parameters. The influence of depth of irregularity and non-homogeneity parameters on phase velocity has been studied.

Dispersion of horizontally polarized shear waves in an irregular non-homogeneous self-reinforced crustal layer over a semi-infinite self-reinforced medium

Propagation of a Love wave in an initially stressed fluid-saturated anisotropic porous layer with an irregular boundary sandwiched between two isotropic half-spaces has been studied. The irregularity is assumed to be rectangular, and the perturbation method is used to obtain the displacement field in the porous layer. Finally, the dispersion relation for the assumed model is obtained, and the result is compared with those derived for the flat layer theory. The effect of porosity, initial stress, and irregularity of the porous layer in phase velocity is studied and shown graphically.

Dispersion of Love Wave Propagating in Irregular Anisotropic Porous Stratum under Initial Stress

The present paper is concerned with the study of propagation of torsional waves in an inhomogeneous isotropic layer whose material properties vary harmonically with a space variable, lying over a semi-infinite inhomogeneous isotropic half-space. The closed form solutions for the displacement in the layer and half-space are obtained separately. The dimensionless phase velocity has been plotted against dimensionless wave number and scaled wave number for different values of inhomogeneity parameters. The effects of inhomogeneity have been shown in the dispersion curves using 2D and 3D plot.

Propagation of torsional waves in an inhomogeneous layer over an inhomogeneous half-space

The aim of the paper is to study the shear wave propagation in a viscoelastic layer over a semi-infinite viscoelastic half space due to irregularity in the viscoelastic layer. It is of great interest to study the propaga-tion of shear waves in the assumed medium having a non planar boundary due to its similarity to most of the real situations. The perturbation method is applied to find the displacement field. The effect of complex wave number on dissipation factor is analysed. Finally, as an application, the result obtained has been used to get the reflected field in viscoelastic layer when the shear wave is incident on an irregular boundary in the shape of parabolic irregularity as well as triangular notch. It is observed that the amplitude of this reflected wave decreases with increasing length of the notch, and increases with increasing depth of the irregularity.

Propagation of shear waves in viscoelastic medium at irregular boundaries

This paper presents a theoretical study on propagation of torsional surface waves in a homogeneous viscoelastic isotropic layer with Voigt type viscosity over an inhomogeneous isotropic infinite half space. The non-homogeneity in half space is assumed to arise due to exponential variation in shear modulus and density. A closed-form solution has been obtained for the displacement in the layer as well as for a infinite half space. The dispersion and absorption relations for an torsional wave under the assumed geometry have been found. Numerical results are presented for propagation characteristics in terms of a number of non-dimensionalized parameters and have been produced graphically. This study investigates the effect of various parameters, namely non-homogeneity parameter, internal friction, the layer width and complex wave number on dissipation function and phase velocity of the torsional wave. Results in some special cases are also compared with existing solutions available from analytical methods, which show a close agreement.

Propagation of torsional waves in a viscoelastic layer over an inhomogeneous half space

The present paper discusses the frequency equation for torsional waves in a self-reinforced medium. It can be seen that the phase velocity of torsional waves in a self-reinforced rod of circular cross section is influenced by the reinforced parameters. Numerical computation shows that the presence of the reinforcement parameter increases the phase velocity significantly. It has been observed that the velocity of torsional waves coincides with the shear wave velocity when the reinforcement parameters are zero.

V. K. Sharma

Papers

Effect of point source and heterogeneity on the propagation of SH-Waves in a viscoelastic layer over a viscoelastic half space

Propagation of torsional waves in an inhomogeneous layer over an inhomogeneous half-space

Propagation of shear waves in viscoelastic medium at irregular boundaries

Propagation of torsional waves in a viscoelastic layer over an inhomogeneous half space

Torsional Waves in Self-Reinforced Medium