The effects of temperature and fluid pressure on thermal pressurization of pore fluids in faults
Abstract
Thermal pressurization (TP) of pore fluids is expected to be a dominant dynamic weakening mechanism in earthquakes. Frictional heat during an earthquake can pressurize the pore fluids in the fault rocks and cause a reduction in effective normal stress, causing a subsequent reduction in shear stress across the fault at seismic time scales. Physical evidence for TP in the field is scarce, thus most of our knowledge relies on theoretical predictions and more recently, laboratory experiments. The prevailing models for TP do not account for the temperature- and pressure-dependence of the physical properties of the fault materials (e.g., permeability and fluid viscosity), which control the TP process. We study the effects of temperature and fluid pressure on TP for a gouge-filled fault by a one-dimensional numerical model in two scenarios: (1) the physical properties are temperature- and pressure dependent; and (2) thickness of deforming layer of gouge in the fault is also dependent on effective normal stress. We find that, compared to the constant properties case with slip localized on a plane, the fault experiences ~10% more weakening at a faster rate using variable properties, resulting in further limiting the temperature rise in the fault by 33%. Furthermore, fluid and heat transport away from the slip surface (and the associated decrease in effective normal stress) can lead to delocalization from an initial slip-on-a-plane case to a deformation zone up to ~50 μm wide - which in turn inhibits further weakening and can even lead to re-strengthening of the fault during seismic slip.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMS031.0021B
- Keywords:
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- 7215 Earthquake source observations;
- SEISMOLOGY;
- 7240 Subduction zones;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS