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Velocities and anisotropy as seen by upper mantle converted waves
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-96024OAI: oai:DiVA.org:uu-96024DiVA: diva2:170432
Available from: 2007-05-10 Created: 2007-05-10 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Analyses of Seismic Wave Conversion in the Crust and Upper Mantle beneath the Baltic Shield
Open this publication in new window or tab >>Analyses of Seismic Wave Conversion in the Crust and Upper Mantle beneath the Baltic Shield
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Teleseismic data recorded by broad-band seismic stations in the Swedish National Seismic Network (SNSN) have been used in a suite of studies of seismic wave conversion in order to assess the structure of the crust and upper mantle beneath the Baltic Shield. Signals of seismic waves converted between P and S at seismic discontinuities within the Earth carry information on the velocity contrast at the converting interface, on the depth of conversion and on P and S velocities above this depth.

The conversion from P to S at the crust-mantle boundary (the Moho) provides a robust tool to constrain crustal thicknesses. Results of such analysis for the Baltic Shield show considerable variation of Moho depths and significantly improve the Moho depth map. Analysis of waves converted from S to P in the upper mantle reveals a layered lithosphere with alternating high and low velocity bodies. It also detects clear signals of a sharp velocity contrast at the lithosphere-asthenosphere boundary at depths around 200 km.

Delay times of P410s, the conversion from P to S at the upper mantle discontinuity at 410 km depth, were used in a tomographic inversion to simultaneously determine P and S velocities in the upper mantle. The polarisation of P410s was also used to study anisotropy of the upper mantle. Results of these analyses are found to be in close agreement with independently derived results from arrival time tomography and shear-wave splitting analysis of SKS.

The results presented in this thesis demonstrate the ability of converted wave analysis as a tool to detect and image geological boundaries that involve sharp contrasts in seismic properties. The results also show that this analysis can provide means of studying aspects of Earth’s structure that are conventionally studied using other types of seismic data.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 50 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 319
Geophysics, converted waves, Moho, upper mantle, Baltic Shield, tomography, anisotropy, receiver function, Geofysik
National Category
urn:nbn:se:uu:diva-7930 (URN)978-91-554-6919-1 (ISBN)
Public defence
2007-06-15, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2007-05-10 Created: 2007-05-10 Last updated: 2016-05-13Bibliographically approved

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