Resolving Transient Deformation at High Pressure

Many societal hazards and fundamental tectonic processes depend on the mechanical properties of minerals in subduction zones. The pressure and temperature where these materials deform range from surface conditions to greater than 2 GPa and 1200 °C. Experiments have been conducted at nominal steady-state for many of the common minerals at laboratory strain rates, but transient phenomena like slow slip, intermediate depth earthquakes, and post-seismic creep have highlighted the importance of conducting new experiments at relevant pressure, temperature, and low strain rates.

Both increased temporal and measurement resolution are required to study transient phenomena in the lab. In our Griggs apparatus we have modified seal designs to reduce friction and use fluid confining media at low temperatures from 25-600 °C and pressures up to 2 GPa. Additionally, we have added laser interferometers to measure internal load and ram displacement. We show here how we have used these improvements to study friction and attenuation at 1 GPa confining pressure and strain rates as low as 10-9 1/s.