Presentation by Dr. Ben Belzer
Fluid-mediated deformation along the shallow subduction interface: Insights from experiments and natural faults
Abstract:
The shallow segment of subduction plate boundaries (< 15 km depth) hosts diverse modes of fault slip, including slow slip events, tectonic tremor, and large destructive earthquakes. These slip behaviors are thought to be controlled by the mechanical properties of rocks and sediments along the plate boundary, as well as environmental factors such as temperature, lithostatic stress, and pore fluid pressure. Over the past couple of decades, the role of fluids has particularly received growing attention, as geophysical and geological observations suggest that slow earthquakes occur in regions that are fluid-rich and deform at low effective stresses. However, it is still unclear how fluids, through processes such as fault zone alteration and fluid overpressure, affect slip behavior along subduction megathrust faults.
In this talk, I will present evidence from laboratory deformation experiments and natural subduction zone rocks that address the influence of fluids on fault zone rheology and deformation along the shallow subduction interface. Topics will include: (1) the frictional properties of chlorite, a common hydrous mineral in subduction zones, and its potential role in megathrust slip modes; (2) the weakening effects of potassium metasomatism in subducting oceanic crust; and (3) the impacts of different sources of pore pressure generation (e.g., disequilibrium compaction and mineral dehydration reactions) on fault rock microstructure, deformation, and frictional stability in shallow subduction shear zones.
