Book contents
- Frontmatter
- Contents
- Preface
- Part I General background
- Part II Materials science of deformation
- Part III Geological and geophysical applications
- 17 Composition and structure of Earth's interior
- 18 Inference of rheological structure of Earth from time-dependent deformation
- 19 Inference of rheological structure of Earth from mineral physics
- 20 Heterogeneity of Earth structure and its geodynamic implications
- 21 Seismic anisotropy and its geodynamic implications
- References
- Materials index
- Subject index
- Plate section
20 - Heterogeneity of Earth structure and its geodynamic implications
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Part I General background
- Part II Materials science of deformation
- Part III Geological and geophysical applications
- 17 Composition and structure of Earth's interior
- 18 Inference of rheological structure of Earth from time-dependent deformation
- 19 Inference of rheological structure of Earth from mineral physics
- 20 Heterogeneity of Earth structure and its geodynamic implications
- 21 Seismic anisotropy and its geodynamic implications
- References
- Materials index
- Subject index
- Plate section
Summary
Lateral heterogeneity in Earth exists at various scales. Such heterogeneity includes the lateral variation in seismic wave velocities and attenuation as well as the topography on seismic discontinuities. This chapter focuses on the seismological observations on large-scale (~ 100 km or larger) heterogeneity and provides a summary of (i) basic seismological observations on lateral heterogeneity of velocity and attenuation and the depth of seismic discontinuities, and (ii) their geodynamical interpretation. Interpretation of heterogeneity in seismic observations is not straightforward because a variety of factors could cause the lateral variation of seismological observables. However, some important conclusions have been obtained including (i) the large depth variation in the amplitude of velocity anomalies, and (ii) the fact that the ratio of anomalies in S- and P-wave velocities can be naturally interpreted by thermal anomalies, if the nature of anharmonicity and anelasticity is appropriately taken into account. In contrast, inferring chemical heterogeneity from seismological observations is challenging because of either low or poorly known sensitivity of observable parameters to chemical composition. Issues of identifying chemical heterogeneity are discussed including the heterogeneity in major element chemistry as well as heterogeneity in hydrogen (water) content.
Key words seismic tomography, topography on discontinuities, anharmonicity, Grüneisen parameter, anelasticity.
- Type
- Chapter
- Information
- Deformation of Earth MaterialsAn Introduction to the Rheology of Solid Earth, pp. 363 - 390Publisher: Cambridge University PressPrint publication year: 2008