Israporn Sethanant
- MSc (Oregon State University, 2019)
- BSc (Chulalongkorn University, 2016)
Topic
Discovery and Characterization of Earthquakes on Immature Strike-slip Faults with InSAR
School of Earth and Ocean Sciences
Date & location
- Wednesday, August 14, 2024
- 10:00 A.M.
- Bob Wright Centre, Room A319
Examining Committee
Supervisory Committee
- Dr. Edwin Nissen, School of Earth and Ocean Sciences, University of Victoria (Supervisor)
- Dr. Lucinda Leonard, School of Earth and Ocean Sciences, UVic (Member)
- Dr. Kelin Wang, School of Earth and Ocean Sciences, UVic (Member)
- Dr. Tuna Onur, Department of Civil Engineering, UVic (Outside Member)
External Examiner
- Dr. Kathryn Materna, Geological Sciences, University of Colorado Boulder
Chair of Oral Examination
- Dr. Shannon Fargey, Department of Geography, UVic
Abstract
Fault structural maturity describes how fault zones evolve with incremental slip, and may control certain aspects of earthquake rupture behaviour. Immature faults are harder to identify and characterize than mature faults by virtue of their subtle to non-existent topographic and geophysical expressions, and thus pose distinct hazards and risks. Nonetheless, the advent of satellite-borne Interferometric Synthetic Aperture Radar (InSAR) surface deformation mapping has revolutionized our ability to characterize large earthquakes that occur on these hidden faults. By doing so, we can start to recognize common attributes to immature faults that may have important implications for seismic hazard. This is the central theme of this dissertation.
After introducing how InSAR works, I describe how to interpret surface deformation maps for various faulting styles. To explore relations between structural maturity and rupture behaviour, I then employ InSAR to characterize recent earthquakes along immature strike-slip faults in two contrasting tectonic settings: the Eastern California Shear Zone/Walker Lane of California and Nevada, U.S.A., and the Shan Plateau in Laos, Thailand and Myanmar. The main foci are the 2020 Mw 6.5 Monte Cristo Range, Nevada earthquake and the 2019 Mw 6.2 Sainyabuli, Laos earthquake, respectively. In both cases, I tried to characterize the full complexity of the earthquakes by working with collaborators to incorporate independent seismological constraints.
We found certain rupture behaviours common to the Monte Cristo Range and Sainyabuli earthquakes that may be linked to fault structural maturity. Both mainshocks had short (∼20–30 km) fault lengths and pronounced (∼80–90%) shallow slip deficits (SSD) that may reflect off-fault deformation ∼5–10 km from the primary faults, consistent with relocated aftershocks. However, slip profile comparisons with InSAR models of other strike-slip earthquakes suggest that SSD is controlled more by earthquake magnitude than by fault maturity, with smaller earthquakes having the greatest range in SSD and larger ones propagating fully to the surface with more consistency. The Monte Cristo Range earthquake also involved an unusual configuration of crossing faults, likely due to the early stage of evolution of the host fault zone.
The limited geomorphic expression along modelled fault traces of the Monte Cristo Range and Sainyabuli mainshocks raises an alarming concern for seismic hazard assessment. Since immature faults are hard to map, they are often overlooked in seismic hazard calculations. Seismic hazard models may therefore benefit from considering area sources alongside fault sources in both accuracy and comprehensiveness.