Studies of Upper-Plate Deformation at Subduction Zone Plate Boundaries
Open Access
- Author:
- Mckenzie, Kirsty
- Graduate Program:
- Geosciences (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 10, 2022
- Committee Members:
- Charles Ammon, Major Field Member
Kevin Furlong, Chair & Dissertation Advisor
Diane Henderson, Outside Unit & Field Member
Donald Fisher, Major Field Member
Mark Patzkowsky, Program Head/Chair
Eric Kirby, Special Member - Keywords:
- Geodynamics
Active Tectonics
Subduction Zones
Upper-plate Deformation
GPS
Plate Tectonics - Abstract:
- In this dissertation I use observations of upper-plate deformation to constrain the kinematics and dynamics of tectonic processes that occur at subduction zones and within plate boundary transition zones. I combine observations that record deformation over weeks to decades (geodetic observations), tens to hundreds of thousands of years (field observations and geochronology), and millions of years (field observations and plate boundary reconstructions), with earthquake cycle modeling. This research is primarily focused on the Cascadia subduction zone, however the results are applicable across many subduction zones globally. Specific related cases that are highlighted include the Hikurangi margin (New Zealand) and the Nankai trough (SW Japan). The studies in my research range from using observations of slow slip earthquakes to constrain the plate motion direction and forces acting down-dip of the seismogenic zone, to observations of permanent upper-plate deformation to better understand the relationship between shallow mechanical locking on the plate interface and upper-plate deformation. Some key findings I present over several chapters are: (1) a model for the Cascadia subduction zone (and other obliquely-convergence subduction zones) that suggests that loading of the locked region at deep levels is down-dip and thus oblique to the loading direction at shallow levels; (2) a new coupling model for the Cascadia subduction zone that relates the variation in GPS velocities (and permanent deformation) from south to north across the margin to the locations of upper-plate strength (geologic terrane) boundaries; and (3) permanent coastal uplift is not being produced continuously, and instead observations from central Cascadia suggest uplift rates can change significantly over ~20 kyrs.