A high pressure, high temperature gas medium apparatus to measure acoustic velocities during deformation of rock.

A new setup to measure acoustic wave velocities through deforming rock samples at high pressures (up to 1000 MPa), temperatures (up to 700 °C), and differential stresses (up to 1500 MPa) has been developed in a recently refurbished gas medium triaxial deformation apparatus. The conditions span a wide range of geological environments and allow us to accurately measure differential stress and strains at conditions that are typically only accessible in solid medium apparatus. Calibrations of our newly constructed internal furnace up to 1000 MPa confining pressure and temperatures of up to 400 °C demonstrate that the hot zone is displaced downward with increasing confining pressure, resulting in temperature gradients that are minimized by adequately adjusting the sample position.

Fluid pressurisation and earthquake propagation in the Hikurangi subduction zone.

In subduction zones, seismic slip at shallow crustal depths can lead to the generation of tsunamis. Large slip displacements during tsunamogenic earthquakes are attributed to the low coseismic shear strength of the fluid-saturated and non-lithified clay-rich fault rocks. However, because of experimental challenges in confining these materials, the physical processes responsible for the coseismic reduction in fault shear strength are poorly understood.