High Temperature And Pressure Under Hui Long Rock Elastic Wave Velocity And Attenuation

The variations of the elastic properties of gabbro at 100~300℃and 0.5~4.0 GPa and the seismogeological application of the experimental results are discussed based on the measured wave velocities (VP, VS) and quality factor values (QP, QS) of the gabbro. The values of VP, VS, QP and QS increase with pressure from 0.5 GPa to 4.0 GPa at the given temperatures, but decrease in small extent from 100℃to 300℃at the given pressures. Increasing pressure from 0.5 GPa to 2.3 GPa at 300℃, the values of VP, VS, QP and QS increase by 5.9%, 2.7%, 353.8% and 403.4%, respectively; and from 2.3 GPa to 4.0 GPa, by 1.4%, 0.5%, 47.5% and 40.4%, respectively. The variations of velocities and quality factor values may be mainly attributed to the compression of the gabbro sample, and its continuity and elasticity become better at 0.5~2.3 GPa. The gabbro sample almost becomes continuous and elastic medium at 2.3~4.0 GPa, resulting in smaller change of elastic wave velocities and attenuation. The wave velocities and quality factor decrease with increasing temperature because of thermal expansion and density decreasing of gabbro. The experiment results can be used to explain the geophysical observed phenomena that quality factor values are enhanced by stress aggregation in the lithosphere, and the quality factor values may be reduced by rock fracturation and local enrichment of hot fluids in the epicentral areas before and after earthquake occurrences.