Doctoral Dissertations


"Azimuthal anisotropy quantified by teleseismic SKS, SKKS, PKS (“XKS”) and local S wave splitting parameters is used to investigate lithospheric deformation and asthenospheric flow beneath the boundary zone of the North American and Caribbean plates and adjacent areas. A total of 4915 XKS and 1202 pairs of local S wave splitting parameters were obtained at 24 broad band seismic stations. The XKS observations can be divided into two groups based on the spatial distribution of the resulting fast polarization orientations. Those observed on the Caribbean Plate are mostly WNW-ESE which are roughly trench-parallel. In contrast, the fast orientations observed on the North American Plate are dominantly NNE-SSW which are approximately trench-orthogonal and are consistent with those previously observed in southern Mexico to the north of the area of the current study. At most of the stations at which XKS and local S wave splitting parameters are available, the fast orientations from the two types of shear waves are comparable, but the XKS splitting times are about twice of the local S wave splitting times, suggesting that the observed azimuthal anisotropy has contributions from both above and below the subducting oceanic slab. In the Lesser Antilles subduction zone, a thinner than normal transition zone thickness is revealed and is attributable to mantle upwelling along the edges of the slab and slab gaps beneath the area. The transition zone thinning is mostly caused by an uplifted 660 km discontinuity, suggesting that the thermal upwelling may be originated from the lower mantle of the Earth. The uplifted 410 km and depressed 660 km discontinuities in area south of the southern boundary of the Caribbean plate may indicate the existence of cold slab segments"--Abstract, p. iv


Gao, Stephen S.
Liu, Kelly H.

Committee Member(s)

Rogers, J. David
Mickus, Kevin L.
Obrist-Farner, Jonathan
Shi, Yutao


Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Geology and Geophysics


Missouri University of Science and Technology

Publication Date

Fall 2022


x, 54 pages

Note about bibliography

Includes_bibliographical_references_(pages 52-53)


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Document Type

Dissertation - Open Access

File Type




Thesis Number

T 12208