Dissertation
Geodetic investigations of permanent earthquake-cycle deformation at the Makran subduction zone
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2022
DOI: 10.25820/etd.006752
Abstract
In many numerical modeling studies of the Earth system. Crustal deformation in response to earthquake rupture is assumed to be an elastic process, where earthquake-induced strain is recoverable after several earthquake cycles. Inelastic deformation, or permanent damages caused by the earthquake are ignored in under the elastic assumption, leading to inaccurate estimation of earthquake hazard potential, earthquake mechanisms, or fault zone properties. This dissertation focuses on revealing the inelastic behaviors of the Earth during or after large earthquakes, through the application of satellite-based geodetic observations and numerical modeling techniques.
I present the surface strain field of the 2013 Mw7.7 Baluchistan earthquake in southern Pakistan. I invert co-seismic displacement maps generated from pixel-tracking of SPOT-5 optical images for co-seismic surface horizontal strain tensors. I show that co-seismic inelastic surface deformation is localized to a narrow zone about 100-200 m wide on the hanging wall side of the fault. I find that the width of the inelastic deformation zone correlates to fault maturity, and that the permanent surface strains reflect deformation of the fault damage zone.
I monitor the 6.5-year post-seismic deformation following the 2013 Baluchistan earthquake using Sentinel-1 InSAR time-series, and apply finite element modeling to simulate the time-dependent deformation of the Makran accretionary prism. My results show that power-law viscoelastic relaxation of an earthquake stress-induced, low-viscosity zone within the lower accretionary prism contributes to most of the post-seismic deformation. I argue that the low-temperature viscous behavior of the lower Makran wedge results from the high fluid saturation within the accretionary prism.
I conduct inversion for the megathrust coupling model of the Makran subduction zone from interseismic GPS velocity data. I utilize the model resolution matrix to explore possible plate-coupling scenarios that are consistent with the limited spatial resolution afforded by GPS observations. Based on these coupling scenarios, I predict possible future earthquake ruptures, and forward model the corresponding tsunami responses within the western Indian Ocean basin. My results show potential segmentation of the Makran megathrust with varying coupling from west to east, and the largest future earthquake scenario is able to produce tsunami of maximum wave height up to 5 m at major coastal cities in the region.
Details
- Title: Subtitle
- Geodetic investigations of permanent earthquake-cycle deformation at the Makran subduction zone
- Creators
- Guo Cheng
- Contributors
- William Barnhart (Advisor)Shaoyang Li (Committee Member)Emily Finzel (Committee Member)Tom Foster (Committee Member)Bill McClelland (Advisor)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Geoscience
- Date degree season
- Autumn 2022
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.006752
- Number of pages
- xii, 175 pages
- Copyright
- Copyright 2022 Guo Cheng
- Language
- English
- Description illustrations
- Illustrations, charts, graphs, tables, maps
- Description bibliographic
- Includes bibliographical references (pages 109-141).
- Public Abstract (ETD)
In many scientific studies, earthquake-related deformation is assumed to be recoverable after the rupture, and no permanent damage is made. This assumption can lead to inaccurate assessment of earthquake hazard, and mechanical properties of the Earth. In this dissertation, I use satellite observations and modeling methods to measure and simulate the permanent deformation caused by earthquakes.
I use optical satellite images to measure the deformation occurred during the 2013 Baluchistan earthquake. I show that the earthquake generated permanent deformation that is localized to a narrow zone on one side of the fault. I find that the width of this zone correlates to how much total offset the fault has experienced, and that the permanent deformation contributes to the long-term damage around the fault.
I use radar images to monitor the surface deformation after the same earthquake. I apply numerical modeling to simulate the deformation through time. My results show that the earthquake causes a layer of materials underneath the fault to flow during the observation period. This type of flow-like behavior results from high fluid content within the Earth.
I use GPS data to assess the degree of frictional energy stored on the Makran megathrust. I generate possible earthquake events, and predict the corresponding tsunami responses within the western Indian Ocean basin. My results show that the frictional energy stored on the megathrust varies from west to east, and that future earthquakes are able to produce tsunami with wave height reaching 5 m at major port cities in the region.
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984362959202771
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