A High-pressure, High-temperature Apparatus for Studies of Seismic Wave Dispersion and Attenuation

An apparatus is described which provides for the investigation of viscoelasticity/anelasticity in geologic and related materials under conditions of high pressure and temperature. Cylindrical specimens are tested in torsion — a geometry particularly well suited to shear mode observations at the low strain amplitudes of the linear regime. Forced oscillation experiments allow the measurement of dispersion and attenuation at the low frequencies of teleseismic wave propagation. The conduct of complementary forced oscillation and creep tests allows recoverable anelastic strains to be distinguished from those of permanent viscous deformation. It has been demonstrated that robust measurements can be made at strain amplitudes below 10−5 and frequencies of 1 mHz−1 Hz, under P-T conditions to 300 MPa and 1200°C. The prospects for further development of this facility are outlined.