A Seismological Perspective on the Lithosphere-Asthenosphere Boundary

Ford, Heather Anne

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Year:: 2013
Contributor:: Ford, Heather Anne (creator); Fischer, Karen (Director); Forsyth, Donald (Reader); Hirth, Greg (Reader); Saal, Alberto (Reader); Abers, Geoff (Reader); Brown University. Geological Sciences (sponsor)
Genre:: theses
Subject:: receiver functions; asthenosphere; San Andreas Fault system; Seismology; Lithosphere; Cratons; Australia; North America
Extent:: 18, 172 p.
DOI: https://doi.org/10.7301/Z0MW2FG1

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Abstract:: The lithosphere-asthenosphere boundary is the world’s most ubiquitous plate boundary system, separating the high viscosity lithosphere from the underlying convecting mantle asthenosphere. Thoroughly characterizing the properties of the lithosphere-asthenosphere boundary can help us to improve our understanding of the behavior of tectonic plates and the attendant issues surrounding plate tectonic theory, mantle dynamics and the evolution of continents and oceans. The most fundamental questions that this dissertation explores are 1) what are the seismic properties of the lithosphere-asthenosphere boundary and 2) what do these results imply about the physical properties of the mantle at the boundary? In chapters one and four, we use Sp scattered wave receiver function analysis, an increasingly popular tool for imaging variations in velocity gradient structure, to image and characterize the seismic and physical properties of the lithosphere-asthenosphere boundary, and other discontinuity structure, beneath Australia (chapter one) and across the San Andreas fault system (chapter 4). The findings discussed in these chapters have important implications not just for the lithosphere-asthenosphere boundary, but for our understanding of the formation and evolution of cratonic lithosphere (chapter 1) and extent and geometry of the San Andreas fault system within the deep mantle lithosphere (chapter 4). Chapter two addresses the effects of seismic anisotropy, which is thought to be an important property of the upper mantle, on Sp receiver function analysis. We find that the effect of anisotropy on Sp receiver functions is complicated, and is a function of both the orientation and type of anisotropy present in the earth and the polarization of the incident S-wave. The work in chapter two also allows us to test the hypothesis that discontinuity structure observed within the North American craton is related to changes in azimuthal anisotropy. In chapter three, the relationship between viscosity and velocity are explored beneath cratonic North America. Larger than expected velocities, even when taking into account compositional effects, suggests that while our understanding of the cratons is improving with time, there are still significant gaps in our knowledge of the structure of the cratonic lithosphere.
Notes:: Thesis (Ph.D. -- Brown University (2013)

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Rights: In Copyright
Restrictions on Use: Collection is open for research.

Citation

Ford, Heather Anne, "A Seismological Perspective on the Lithosphere-Asthenosphere Boundary" (2013). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0MW2FG1

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Earth, Environmental and Planetary Sciences Theses and Dissertations

Theses and Dissertations for the Earth, Environmental and Planetary Sciences department.
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