Constraining East Asia tectonics from full waveform seismic tomography
| dc.contributor.advisor | Grand, Stephen P. | |
| dc.contributor.committeeMember | Zhu, Hejun | |
| dc.contributor.committeeMember | Sandvol, Eric | |
| dc.contributor.committeeMember | Becker, Thorsten | |
| dc.contributor.committeeMember | Ghattas, Omar | |
| dc.creator | Liu, Chujie | |
| dc.date.accessioned | 2024-07-11T01:36:50Z | |
| dc.date.available | 2024-07-11T01:36:50Z | |
| dc.date.created | 2023-12 | |
| dc.date.issued | 2023-12 | |
| dc.date.submitted | December 2023 | |
| dc.date.updated | 2024-07-11T01:36:50Z | |
| dc.description.abstract | East Asia is a unique place to study plate tectonics due to its complicated tectonic history. In this dissertation, I use full waveform seismic tomography to study the seismic structure of the crust and mantle beneath East Asia. The high-resolution 3-D seismic model provides new insights into tectonic processes including oceanic subduction, continental collision, lithospheric evolution, and intraplate volcanism. The model reveals narrow and strong linear fast anomalies associated with subduction zones in the west Pacific and Southeast Asia. These subducting slabs exhibit varying depth extents and geometries. Notably, different mantle structures beneath the India-Asia continental collision zone are observed, compared to oceanic slabs. My analysis suggests that cratonic Indian lithosphere collided with Eurasian plate around 25 Ma, subsequently northward underthrusting beneath Tibet horizontally. Consequently, rheologically weaker and less buoyant mantle lithosphere beneath north-central Tibet has undergone thickening, destabilization, and delamination. The model further reveals isolated lithospheric fragments within the mantle transition zone and lower mantle beneath the collision zone. These observations suggest that for non-cratonic continental collision, discontinuous blobs of lithosphere sinking into the deeper mantle is a common phenomenon, as opposed to the classical oceanic subduction. My results emphasize the important role of rheological properties of continental lithospheres in shaping the dynamics of continental collision. Furthermore, my model shows extensive slow anomalies beneath Southeast Asia, with their complex geometry challenging a simple plume interpretation. Instead, these anomalies are more likely linked to deep subduction-induced mantle upwelling, as subducted slabs are imaged in the mantle transition zone within this region. I next use full waveform inversion to investigate 3-D seismic radial and azimuthal anisotropy structures beneath East Asia. The model shows a decrease in the amplitude of anisotropy with increasing depth, indicative of a transition in the deformation mechanism from dislocation creep in the shallow upper mantle to diffusion creep in the deeper upper mantle. My model also suggests subduction-induced rotational corner flows and trench-parallel sub-slab flows around the Ryukyu slabs. Moreover, a significant change in the direction of azimuthal anisotropy beneath the Japan subduction zone is observed around 400 km depth. Finally, I discuss possible future research opportunities to improve the current seismic model. | |
| dc.description.department | Geological Sciences | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | ||
| dc.identifier.uri | https://hdl.handle.net/2152/125994 | |
| dc.identifier.uri | https://doi.org/10.26153/tsw/52539 | |
| dc.language.iso | en | |
| dc.subject | Full waveform inversion | |
| dc.subject | East Asia | |
| dc.subject | Seismic tomography | |
| dc.subject | Plate tectonics | |
| dc.title | Constraining East Asia tectonics from full waveform seismic tomography | |
| dc.type | Thesis | |
| dc.type.material | text | |
| thesis.degree.department | Geological Sciences | |
| thesis.degree.grantor | The University of Texas at Austin | |
| thesis.degree.name | Doctor of Philosophy |
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