Deformation Processes Throughout the Earthquake Cycle

Open Access
Author:
Herman, Matthew William
Graduate Program:
Geosciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
April 03, 2017
Committee Members:
  • Kevin Patrick Furlong, Dissertation Advisor
  • Kevin Patrick Furlong, Committee Chair
  • Charles James Ammon, Committee Member
  • Donald Myron Fisher, Committee Member
  • Karl Martin Reichard, Outside Member
  • Christelle Wauthier, Committee Member
  • Rob Govers, Special Member
Keywords:
  • Geodynamics
  • Geophysics
  • Earthquakes
  • Finite Element Modeling
  • Subduction Zones
  • Rheology
Abstract:
This dissertation presents observational and modeling analyses of deformation processes acting before, during, and after large earthquakes. Both seismic and geodetic observations of earthquakes and their foreshock/aftershock sequences are used to determine event locations and source parameters. Geodetic observations also provide constraints on aseismic processes, such as slow slip, inter-seismic loading, and post-seismic relaxation. Case studies include the 2011 Mw 9.0 Tohoku, Japan, the 2013 Mw 8.0 Santa Cruz Islands, the 2014 Mw 6.3 Mae Lao, Thailand, the 2014 Mw 8.2 Iquique, Chile, the 2015 Mw 8.3 Illapel, Chile, and the 2016 Mw 5.7 Christchurch, New Zealand earthquakes. Geophysical observations of these events are applied in conjunction with a variety of numerical modeling approaches to develop improved earthquake cycle deformation frameworks. Models of fault slip in an elastic half-space are applied during the co-seismic stage to compute surface displacements and stress changes. These stress changes are interpreted to trigger subsequent seismicity in nearby regions and induce other types of postseismic deformation. Some of the observations are not compatible with these elastic half-space models, so finite element modeling approaches are used to further explore the deformation in more rheologically realistic systems. These models include simulations of inter-seismic deformation around a heterogeneous frictional plate boundary interface, accumulation and release of strain throughout each stage of the earthquakes cycle, and the spatial patterns of loading in a rheologically layered upper plate. By integrating observations and models, these studies highlight the importance of rheological heterogeneity, strain rate, and deformation history in earthquake cycle processes.