Investigating the Earthquake Cycle on Multiple Temporal and Spatial Scales Using Satellites and Simulations

Citation

Stephenson, Oliver Laurent (2023) Investigating the Earthquake Cycle on Multiple Temporal and Spatial Scales Using Satellites and Simulations. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ha9m-4p17. https://resolver.caltech.edu/CaltechTHESIS:08082022-055217161

Abstract

The motion of the Earth's tectonic plates creates a gradual accumulation of stress at their boundaries, followed by a rapid release in earthquakes, a process known as the earthquake cycle. Studying this process is important because of the hazards earthquakes pose, but presents challenges due to the multi-scale nature of the problem—stresses build up over hundreds to thousands of years, while earthquakes break narrow fault zones in a matter of seconds. In this thesis, we combine a variety of techniques to study the earthquake cycle on multiple temporal and spatial scales, including satellite-based interferometric synthetic aperture radar (InSAR) to observe the slow deformation of the Earth over wide areas, and high-performance computational simulations to model faults during earthquakes. We begin by presenting a method for removing the signal of plate-tectonic motion in large-scale InSAR measurements, allowing for better observation of small ground deformations. We then use these corrections to study the Makran subduction zone, on the Iran-Pakistan border. Our InSAR-derived ground velocity map can resolve motions at the level of millimeters per year over an area of nearly one million square kilometers, and we use it to place constraints on the degree of coupling on the subduction megathrust. Next, we show how InSAR can be combined with deep learning techniques to rapidly map earthquake damage in all weather conditions, day and night. Such products will hopefully prove useful in future disaster response. Finally, we present computational simulations of dynamic earthquake ruptures with enhanced dynamic weakening due to thermal pressurization. We apply our simplified model to the creeping section of the San Andreas Fault, which is generally thought to be a barrier to earthquake rupture. Our results show how thermal pressurization can allow earthquakes to propagate partially or completely through the creeping section for a range of physically reasonable parameters. Our work illustrates how results from multiple fields can be combined to deliver new insights into the earthquake cycle and the hazards that it poses.

Thesis Files