The Nature of Crustal Seismic Heterogeneity: A Case Study From the Grenville Province
- 294 Downloads
Over the range of scales for which most seismic reflection data contain information, lithologic variation is one of the major sources of heterogeneity in the crystalline crust. This is particularly true at depths greater than ~10 to 15 km where most of the fractures and microfractures that contribute to upper crustal heterogeneity are closed. The spatial distribution of lithologic heterogeneity is a function of the range of magmatic and tectonic processes that progressively distribute and redistribute the various lithologic components of the crust (the “tectonic roulette” of Fountain and Salisbury, 1981). Although the seismic reflection wavefield responds indirectly to lithologic variation, it is directly responsive to fluctuations of acoustic impedance that are more closely coupled to mineralogy than lithology. Accordingly, pressure and temperature variations that modify mineralogy, but not bulk chemistry, combine with lithologic variation to play both static and dynamic roles in defining the heterogeneity of the Earth’s crust.
KeywordsShear Zone Reflection Coefficient Seismic Data Seismic Reflection Acoustic Impedance
Unable to display preview. Download preview PDF.
- Gibson, B. S., and Levander, A. R., 1988, Modeling and processing of scattered waves in seismic reflection surveys, Geophysics 54:466–478.Google Scholar
- Gibson, B. S., and Levander, A. R., 1990, Apparent layering in common-midpoint stacked images of two-dimensionally heterogeneous targets, Geophysics 55:1466–1477.Google Scholar
- Goff, J. A., and Levander, A., 1996, Incorporating “sinuous connectivity” into stochastic models of crustal heterogeneity: Examples from the Lewisian gneiss complex, Scotland, the Franciscan formation, California, and the Hafafit gneiss complex, Egypt, J. Geophys. Res. 101:8489–8501.CrossRefGoogle Scholar
- Indares, A., 1997, Grt-Ky clinopyroxenites and Grt-Ky restites from the Manicouagan Imbricate Zone: An unusual case of high P-T metamorphism in the Grenville Province, Can. Mineral. 35:1161–1171.Google Scholar
- Wu, R-S., Spatial coherences of seismic data and the application to characterization of small-scale heterogeneities, this volume.Google Scholar