Thesis
A viscous accretionary prism: InSAR observations following the 2013 Baluchistan, Pakistan earthquake
University of Iowa
Master of Science (MS), University of Iowa
Summer 2018
DOI: 10.17077/etd.zbkaerx3
Abstract
Geodetic observations are commonly used to make inferences about the rheology of the lower crust and mantle, frictional properties of faults, and the structure of the Earth following an earthquake. On 24 September 2013, an Mw 7.7 earthquake ruptured a 200 km segment of the Hoshab fault in southern Pakistan. The Hoshab fault is located in the Makran accretionary prism, one of the widest emergent accretionary prisms on Earth. Interferometric synthetic aperture radar (InSAR) time series observations beginning 15 months after the 2013 earthquake capture a large displacement transient in the hanging wall of the Hoshab fault. Using simulations of viscoelastic relaxation and inversions for afterslip along five candidate fault geometries, I find that afterslip alone cannot account for the displacement observed in time series. Instead, I find that the observations can be explained by viscoelastic relaxation of a mechanically weak (viscosity on the order of 1017-1018 Pa s), shallow (>6 km) weak layer within the accretionary prism. First order results indicate this weak layer is between 8-12 km thick with a power law (n=3.5) rheology, and that viscoelastic relaxation is accommodated by dislocation creep at low temperatures. The weak nature of the Makran accretionary wedge may be driven by high pore fluid pressure from hydrocarbon development and underplated sediments.
Details
- Title: Subtitle
- A viscous accretionary prism: InSAR observations following the 2013 Baluchistan, Pakistan earthquake
- Creators
- Katherine Elizabeth Peterson - University of Iowa
- Contributors
- William D. Barnhart (Advisor)Emily S. Finzel (Committee Member)Jane A. Gilotti (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Geoscience
- Date degree season
- Summer 2018
- DOI
- 10.17077/etd.zbkaerx3
- Publisher
- University of Iowa
- Number of pages
- vii, 65 pages
- Copyright
- Copyright © 2018 Katherine Elizabeth Peterson
- Comment
This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/.
- Language
- English
- Date submitted
- 11/19/2018
- Description illustrations
- color illustrations, color maps
- Description bibliographic
- Includes bibliographical references (pages 29-38).
- Public Abstract (ETD)
After an earthquake, deformation of the Earth’s surface in the surrounding region can continue for multiple years. Studying and modeling this deformation makes it possible to learn more about the structure of the Earth in the vicinity of an earthquake, such as information about the viscosity and depths of different mechanical layers. In September 2013, a large earthquake occurred along the Hoshab fault in southern Pakistan in the Makran accretionary prism. The Makran accretionary prism is a weak structure that is the result of active plate convergence in the region. In this study, I use satellite observations of the region surrounding the 2013 earthquake in the years after the event to constrain the mechanical properties of the Makran accretionary prism. I examine both spatial and temporal features of the displacement captured by satellite observations and determine that viscoelastic relaxation of a weak layer within the accretionary prism is the cause of the deformation currently active in the area surrounding the Hoshab fault. These findings have important implications for the mechanics of accretionary prisms.
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9983776998702771
Metrics
80 File views/ downloads
131 Record Views