Structure and mechanics of the subducted Gorda plate: constrained by afterslip simulations and scattered seismic waves

Subduction zones host the greatest earthquakes on earth and pose great threat to human society. The largest slip in megathrust earthquakes often occurs in the 10–50 km depth range, yet seismic imaging of the material properties in this region has proven difficult. This thesis focuses on developing methods to utilize high frequency (2–12 Hz) seismic waves scattered from the megathrust plate interface to constrain its fine-scale velocity structures and to investigate the relationship between velocity structures and megathrust slip behaviors. Chapter 2 investigates the locking condition of the subducted Gorda plate by simulating afterslip that would be expected as a result of the stress changes from offshore strike-slip earthquakes. Chapter 3 develops array analysis methods to identify P-to-S and S-to-P seismic converted phases that convert at the subducted Gorda plate interface from local earthquakes and uses them to constrain the geometry and material properties of the plate boundary fault of the subducted Gorda plate between 5–20 km depth. Chapters 4 and 5 use a dense nodal array and numerical modeling methods to study the seismic guided waves that propagate along the thin low velocity layer at the boundary of the subducted Gorda plate. Taken together, our results indicate that material properties of the subduction plateboundary fault is highly heterogeneous and the plate-boundary fault is potentially contained in a low velocity layer with significant porosity and fluid content at seismogenic depths.

Grantor dc:publisher

Massachusetts Institute of Technology and Woods Hole Oceanographic Institution

Year dc:date.issued

2021

Author dc:creator

• Gong, Jianhua

Advisors dc:contributor.advisor

• McGuire, Jeffrey J.
• Lizarralde, Daniel

• Subduction zone
• Scattered seismic waves
• Plate boundary

Language dc:language.iso

en_US

DOI

10.1575/1912/26541

OAI identifier oai:identifier

oai:darchive.mblwhoilibrary.org:1912/26541