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Title: Global seismic imaging of lithospheric discontinuities using SS precursors
Author: Tharimena, Saikiran
ISNI:       0000 0004 6347 6559
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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Seismic imaging of the lithospheric discontinuities, primarily the base of the lithosphere can provide valuable constraints on the nature of the lithosphere-asthenosphere system, which is vital to our understanding of plate tectonics and mantle dynamics. However, self-consistently imaging, characterizing and relating the lithospheric discontinuities beneath different tectonic environments has been challenging. Understanding the characteristics and defining mechanism(s) of the lithospheric discontinuities can shed light on the formation mechanism and possibly the origin of these discontinuities. This study focuses on seismically imaging the discontinuity structure using SS precursors beneath three unique tectonic environments; the Ontong Java Plateau (OJP), the Pacific Ocean and the continents. SS precursors resolve discontinuities at 28 ± 4 km, consistent with a Moho, a mid-lithospheric discontinuity (MLD) at 80 ± 5 km, and a deeper negative discontinuity at 282 ± 7 km depth beneath the Ontong Java Plateau. The Pacific Ocean is characterized by a sharp, pervasive velocity discontinuity at 30-80 km depth with a 3-15% shear velocity drop over < 21 km depth. The discontinuity increases in depth with age from the ridge to 36 ± 9 My along the 1100 °C conductive cooling isotherm. Beneath older seafloor, the discontinuity is at a mean depth of 60 ± 1.5 km. Finally, SS precursors resolve a discontinuity at 80-121 km depth beneath some continents, consistent with observations of an MLD. In addition, all continental interiors, except India, are characterized by a sharp discontinuity at 130-190 km depth, well-correlated with the depth extent of the lithosphere from diamond thermobarometry and also the transition from coarse-to-deformed xenolith textures. The amplitude and sharpness of the discontinuities imaged beneath the OJP, the Pacific Ocean and the continents suggest that causative mechanisms such as composition, anisotropy and/or melt may be required along with temperature to explain their origin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available