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Jeffrey Joseph McGuire and Daniel Lizarralde. Gong, Jianhua Joint Program in Marine Geology and Geophysics. Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences. Woods Hole Oceanographic Institution. Joint Program in Marine Geology and Geophysics Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Woods Hole Oceanographic Institution Massachusetts Institute of Technology. Department of Ocean Engineering p------ 2021-06-04T17:20:08Z 2021-06-04T17:20:08Z 2021 2021 https://hdl.handle.net/1721.1/130902 1252628245 Thesis: Ph. D., Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February, 2021 Cataloged from the official PDF of thesis. Includes bibliographical references (pages 175-198). Subduction zones host the greatest earthquakes on earth and pose great threat to human society. The largest slip in megathrust earthquakes often occurs in the 10-50 km depth range, yet seismic imaging of the material properties in this region has proven difficult. This thesis focuses on developing methods to utilize high frequency (2-12 Hz) seismic waves scattered from the megathrust plate interface to constrain its fine-scale velocity structures and to investigate the relationship between velocity structures and megathrust slip behaviors. Chapter 2 investigates the locking condition of the subducted Gorda plate by simulating afterslip that would be expected as a result of the stress changes from offshore strike-slip earthquakes. Chapter 3 develops array analysis methods to identify P-to-S and S-to-P seismic converted phases that convert at the subducted Gorda plate interface from local earthquakes and uses them to constrain the geometry and material properties of the plate boundary fault of the subducted Gorda plate between 5-20 km depth. Chapters 4 and 5 use a dense nodal array and numerical modeling methods to study the seismic guided waves that propagate along the thin low velocity layer at the boundary of the subducted Gorda plate. Taken together, our results indicate that material properties of the subduction plateboundary fault is highly heterogeneous and the plate-boundary fault is potentially contained in a low velocity layer with significant porosity and fluid content at seismogenic depths. by Jianhua Gong. Ph.D. Ph.D. Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution) 198 pages eng Massachusetts Institute of Technology MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided. http://dspace.mit.edu/handle/1721.1/7582 Joint Program in Marine Geology and Geophysics. Earth, Atmospheric, and Planetary Sciences. Woods Hole Oceanographic Institution. Structure and mechanics of the subducted Gorda Plate : constrained by afterslip simulations and scattered seismic waves Thesis application/pdf 2021-06-04T17:20:08Z Publication Doctoral OceanEng EAPS unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="023e5c4c-619e-41f6-b456-a22421ecd501"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Structure and mechanics of the subducted Gorda Plate : constrained by afterslip simulations and scattered seismic waves</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2021</PublicationDate> <Authors> <Author> <DisplayName>Gong, Jianhua</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Joint Program in Marine Geology and Geophysics.</Keyword> <Keyword>Earth, Atmospheric, and Planetary Sciences.</Keyword> <Keyword>Woods Hole Oceanographic Institution.</Keyword> <Abstract>Subduction zones host the greatest earthquakes on earth and pose great threat to human society. The largest slip in megathrust earthquakes often occurs in the 10-50 km depth range, yet seismic imaging of the material properties in this region has proven difficult. This thesis focuses on developing methods to utilize high frequency (2-12 Hz) seismic waves scattered from the megathrust plate interface to constrain its fine-scale velocity structures and to investigate the relationship between velocity structures and megathrust slip behaviors. Chapter 2 investigates the locking condition of the subducted Gorda plate by simulating afterslip that would be expected as a result of the stress changes from offshore strike-slip earthquakes. Chapter 3 develops array analysis methods to identify P-to-S and S-to-P seismic converted phases that convert at the subducted Gorda plate interface from local earthquakes and uses them to constrain the geometry and material properties of the plate boundary fault of the subducted Gorda plate between 5-20 km depth. Chapters 4 and 5 use a dense nodal array and numerical modeling methods to study the seismic guided waves that propagate along the thin low velocity layer at the boundary of the subducted Gorda plate. Taken together, our results indicate that material properties of the subduction plateboundary fault is highly heterogeneous and the plate-boundary fault is potentially contained in a low velocity layer with significant porosity and fluid content at seismogenic depths.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>