Methods for Seismic Wave Propagation on Local and Global Scales with Finite Differences

Figure 2.16: Models, seismograms and maximum amplitude distributions for two models with a fault widening towards the surface and a low velocity layer on top.. Figure 2.17: Selected seismograms, amplitude spectra and envelopes for the two models with a fault widening towards the surface and a low velocity layer on top .. Figure 4.10: Seismogram comparison of synthetics calculated with the reflectivity method and PSVaxi for PREM with an additional low-velocity layer on top to the CMB………………......72 Figure 04.11: Envelope stacks for five different scattering regimes compared with data………………………………………………………73 xiv Preface xv Preface This thesis is based on three publications which cover the development of methods for numerical calculation of the seismic wave field and their application to local and global problems: Chapter 2 resembles closely the publication Three-dimensional calculations of fault zone guided waves in various irregular structures (Jahnke, Igel and Ben-Zion, 2002). In addition, it contains my contributions to the publication Numerical simulation of fault zone trapped waves: accuracy and 3-D effects (Igel, Jahnke and Ben-Zion, 2002). These contributions are (1) the verification of the applied finite-difference modelling method, (2) simulations of two fault models: the shallow fault model and the y-shaped fault model, and (3) wave propagation snapshots for the bottleneck fault model and the laterally disrupted fault model. The related Figures were published in Igel, Jahnke, Ben-Zion (2002), whereas the corresponding discussion is original to this dissertation. Section 2.5.7 " Sources outside shallow faults " contains a Figure from the publication Guided waves from sources outside faults: an indication for shallow fault zone structure? (Fohrmann, Igel, Jahnke and Ben-Zion, 2004), the corresponding discussion is original to this dissertation. Chapter 3 resembles the publication Global SH-wave propagation using a parallel axi-symmetric spherical finite-difference scheme (Jahnke, Thorne, Cochard and Igel, 2008). This publication originally contains a section with an application of the method to whole mantle scattering. This application is substantially a contribution of coauthor Michael S. Thorne and thus is not included here in original form. Instead, selected Figures of this section are shown and individually discussed in section 3.5. Chapter 4 summarises the development and first applications of a code for P-SV wave propagation in global axi-symmetric geometries. Our knowledge of the inner Earth's structure gained by multidisciplinary studies is to a large extent based on seismological results. The reason for this success of seismology in geosciences is caused by the large amount of information about …