{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/50423"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/50423","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Wavefront Healing and Tomographic Resolution of Mantle Plumes","abstract":"To investigate seismic resolution of deep mantle plumes as well as the robustness of the anti-correlation between bulk sound speed and S wave speed imaged in the lowermost mantle, we use a Spectral Element Method (SEM) to simulate global seismic wave propagation in 3-D wavespeed models and measure frequency-dependent P-, S-, Pdiff- and Sdiff-wave traveltime anomalies caused by plume structures in the lowermost mantle. We compare SEM time delay measurements with calculations based on ray theory and show that an anti-correlation between bulk sound speed and S-wave speed could be produced as an artifact. This is caused by different wavefront healing effects between P waves and S waves in thermal plume models. The bulk sound speed structure remains poorly resolved when P-wave and S-wave measurements are at different periods with similar wavelength. The differences in wave diffraction between the two types of waves depend on epicentral distance and wave frequency. The artifact in anti-correlation is also confirmed in tomographic inversions based on ray theory using Pdiff and Sdiff time delay measurements made on the SEM synthetics. This indicates a chemical origin of \"superplumes\" in the lowermost mantle may not be necessary to explain observed seismic traveltimes. The same set of Pdiff and Sdiff measurements are inverted using finite-frequency tomography based on Born sensitivity kernels. We show that wavefront healing effects can be accounted for in finite-frequency tomography to recover the true velocity model.","abstract_html":"To investigate seismic resolution of deep mantle plumes as well as the robustness of the anti-correlation between bulk sound speed and S wave speed imaged in the lowermost mantle, we use a Spectral Element Method (SEM) to simulate global seismic wave propagation in 3-D wavespeed models and measure frequency-dependent P-, S-, Pdiff- and Sdiff-wave traveltime anomalies caused by plume structures in the lowermost mantle. We compare SEM time delay measurements with calculations based on ray theory and show that an anti-correlation between bulk sound speed and S-wave speed could be produced as an artifact. This is caused by different wavefront healing effects between P waves and S waves in thermal plume models. The bulk sound speed structure remains poorly resolved when P-wave and S-wave measurements are at different periods with similar wavelength. The differences in wave diffraction between the two types of waves depend on epicentral distance and wave frequency. The artifact in anti-correlation is also confirmed in tomographic inversions based on ray theory using Pdiff and Sdiff time delay measurements made on the SEM synthetics. This indicates a chemical origin of "superplumes" in the lowermost mantle may not be necessary to explain observed seismic traveltimes. The same set of Pdiff and Sdiff measurements are inverted using finite-frequency tomography based on Born sensitivity kernels. We show that wavefront healing effects can be accounted for in finite-frequency tomography to recover the true velocity model.","abstract_has_math":false,"creators":["Xue, Jing"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Geosciences","degree_department":"Geosciences","school":null,"contributors":[],"advisors":[],"committee_chairs":["Zhou, Ying"],"committee_members":["King, Scott D.","Hole, John A."],"year":2014,"date_issued":"2014-08-26","date_published":"2014-08-26","updated_at":"2026-07-22T22:18:41Z","subjects":["Seismic tomography","Computational seismology","Theoretical seismology","Wave scattering and diffraction","Wave propagation"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:3572"],"render_values":[{"text":"vt_gsexam:3572","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/50423","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Zhou, Ying"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["King, Scott D.","Hole, John A."]},{"key":"dc:contributor.department","label":"Department","values":["Geosciences"]},{"key":"dc:creator","label":"Author","values":["Xue, Jing"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-08-27T08:00:44Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-08-27T08:00:44Z"]},{"key":"dc:date.issued","label":"Date","values":["2014-08-26"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geosciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Seismic tomography","Computational seismology","Theoretical seismology","Wave scattering and diffraction","Wave propagation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:3572"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/50423"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["To investigate seismic resolution of deep mantle plumes as well as the robustness of the anti-correlation between bulk sound speed and S wave speed imaged in the lowermost mantle, we use a Spectral Element Method (SEM) to simulate global seismic wave propagation in 3-D wavespeed models and measure frequency-dependent P-, S-, Pdiff- and Sdiff-wave traveltime anomalies caused by plume structures in the lowermost mantle. We compare SEM time delay measurements with calculations based on ray theory and show that an anti-correlation between bulk sound speed and S-wave speed could be produced as an artifact. This is caused by different wavefront healing effects between P waves and S waves in thermal plume models. The bulk sound speed structure remains poorly resolved when P-wave and S-wave measurements are at different periods with similar wavelength. The differences in wave diffraction between the two types of waves depend on epicentral distance and wave frequency. The artifact in anti-correlation is also confirmed in tomographic inversions based on ray theory using Pdiff and Sdiff time delay measurements made on the SEM synthetics. This indicates a chemical origin of \"superplumes\" in the lowermost mantle may not be necessary to explain observed seismic traveltimes. The same set of Pdiff and Sdiff measurements are inverted using finite-frequency tomography based on Born sensitivity kernels. We show that wavefront healing effects can be accounted for in finite-frequency tomography to recover the true velocity model."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Wavefront Healing and Tomographic Resolution of Mantle Plumes"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Zhou, Ying"],"dc:contributor.committeemember":["King, Scott D.","Hole, John A."],"dc:contributor.department":["Geosciences"],"dc:creator":["Xue, Jing"],"dc:date.accessioned":["2014-08-27T08:00:44Z"],"dc:date.available":["2014-08-27T08:00:44Z"],"dc:date.issued":["2014-08-26"],"dc:description.abstract":["To investigate seismic resolution of deep mantle plumes as well as the robustness of the anti-correlation between bulk sound speed and S wave speed imaged in the lowermost mantle, we use a Spectral Element Method (SEM) to simulate global seismic wave propagation in 3-D wavespeed models and measure frequency-dependent P-, S-, Pdiff- and Sdiff-wave traveltime anomalies caused by plume structures in the lowermost mantle. We compare SEM time delay measurements with calculations based on ray theory and show that an anti-correlation between bulk sound speed and S-wave speed could be produced as an artifact. This is caused by different wavefront healing effects between P waves and S waves in thermal plume models. The bulk sound speed structure remains poorly resolved when P-wave and S-wave measurements are at different periods with similar wavelength. The differences in wave diffraction between the two types of waves depend on epicentral distance and wave frequency. The artifact in anti-correlation is also confirmed in tomographic inversions based on ray theory using Pdiff and Sdiff time delay measurements made on the SEM synthetics. This indicates a chemical origin of \"superplumes\" in the lowermost mantle may not be necessary to explain observed seismic traveltimes. The same set of Pdiff and Sdiff measurements are inverted using finite-frequency tomography based on Born sensitivity kernels. 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