The Effect of Sediment Porosity and Permeability on Plate Boundary Foreces
Open Access
- Author:
- Gildow, Marie Christine
- Area of Honors:
- Geosciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Demian Saffer, Thesis Supervisor
Demian Saffer, Thesis Supervisor
Dr. Peter J Heaney, Thesis Honors Advisor - Keywords:
- sediment consolidation
overconsolidation
Nankai Trough
permeability
megasplay fault - Abstract:
- Tectonic plate subduction boundaries include a complex system of numerous faults, and are often sites of major earthquakes. The ability to better characterize the mechanics of fault systems has implications for greater understanding and modeling of pore pressure, stress, and strength at subduction boundaries. Previous studies suggest that high pore fluid pressures leading to lower effective stress on sediments could ease tectonic movement by causing mechanical weakness at boundaries and allow aseismic slip. Consolidation testing was done on three samples from below a megasplay fault near the Nankai Trough off the coast of Japan in order to determine preconsolidation stress and compaction characteristics. The tests showed all three samples to be overconsolidated, indicating that pore fluid pressure is probably not elevated. This is consistent with the high permeabilities of the samples when compared with other studies (e.g. Skarbek and Saffer, 2009). Overconsolidation due to cementation, erosion, and incorrect laboratory methods was explored by consulting the literature, analyzing SEM images, and comparison with borehole data collected at the time of sampling. The implications of overconsolidation and hydraulic conductivity on pore fluid pressures and pore water transport are briefly discussed.