The seismic wavefield. Vol. 1: Introduction and theoretical development (Q2768981)

The transfer of energy from a seismic source, an earthquake or an explosion, to the visible effects at the Earth's surface is carried out by seismic waves. Recently, with the development of global networks and the widespread use of broad-band recording by portable instrumentation, the volume of high-quality, digital seismic observations and the knowledge about seismic waves grew enormously. Thus there arose a need for a book summarizing the new knowledge in the fields of seismic observations and theory. The aim of the present book is to fill this lack focusing on observations of earthquakes and man-made sources from the near source region out to thousands of kilometers from the source. Theories of body waves and surface waves are presented. Thereat, special attention is paid to frequencies above 10 mHz.NEWLINENEWLINEThe issued volume 1 of the present book consists of two parts. Part 1 begins with a survey of the structure of the Earth and the nature of seismic wave propagation using observed seismograms. The treatment is largely descriptive. Mainly isotropic media are considered. First, interactions of plane seismic waves with the Earth's surface and internal boundaries between two solid media, as well as guided and surface waves are discussed. Then the full set of processes, from the generation of seismic waves at the sources, the transmission through the Earth and the record at a seismic station (including seismogram analysis) are explained. It is shown that the forms of body and surface waves at teleseismic distances contain information on both the nature of the seismic sources and the structure of the Earth's interior penetrated by the waves.NEWLINENEWLINE In part 2, the basic elements of the theory of seismic waves propagating in anisotropic media are discussed in more detail. The theory bases on the equilibrium between the prevailing forces and the resistance to deformations of the Earth's inner material, that means on the relation between stress and strain tensors. Part 2 starts with the study of the nature of seismic waves in unbounded, locally homogeneous media. To describe waves in heterogeneous media, an approach using wavefronts and rays is developed. As wave propagation mainly depends on the depth of the seismic eruption under the Earth's surface, the special cases of horizontally and spherically propagating seismic rays are analysed. Basing on these analyses, then more complicated wave propagation in stratified matter is discussed. Further, linear stress-strain relations for applications far from the seismic source are presented, and approaches to take into account near-source nonlinear effects via an equivalent point source are shown. Properties of plane seismic waves travelling in an unbounded medium with varying elastic properties are considered. Then, systematically reflections and transmissions of waves from layers or zones of gradients in plane and spherical stratified media are discussed. There interactions of up- and down-going waves of different types are taken into account. Finally, the construction of total seismic wavefields in cylindrical and spherical coordinate systems are explained.NEWLINENEWLINEThe book will be very valuable to students and researchers in the fields of seismology and petroleum industry. \smallskip