Average Elastic Velocity Research Articles

Lattice Specific Heat and Debye Temperature of Al-Li Alloy.

The lattice dynamics and thermal properties of α-phase Al-Li alloy by solid-solutioning under pressure are studied using our previous microscopic electronic theory. The phonon frequencies of the band and local modes and the lattice specific heat at constant volume are presented theoretically for the Al1-xLix system. The band and local mode frequencies increase with the solubility of Li, and the specific heat decreases except at low temperatures. The Debye temperature for the AI1-xLix system is estimated from the specific heat at low temperatures and from the average elastic velocity. The Debye temperature decreases as Li content increases.

Lattice specific heat of AlCu alloy by solid-solutioning under pressure

The lattice dynamics and thermal properties of AlCu alloy by solid-solutioning under pressure are studied using our previous microscopic electronic theory. The phonon frequencies of the band and local modes and the lattice specific heat at constant volume are presented theoretically for the Al 1− x Cu x system. The band and local mode frequencies increase with the solubility of Cu, and the specific heat decreases except at low temperatures. The Debye temperature for the Al 1− x Cu x , Al 1− x Si x and Al 1− x Ge x systems is estimated from the specific heat at low temperatures and from the average elastic velocity. The Debye temperature decreases with the solubility of Cu, and even stronger with the extended solubility of Si and Ge.

Variations in oceanic layer 2 elastic velocities near Hawaii and their correlation to lithospheric flexure

Analysis of the travel times and amplitude range distributions of both compressional and shear wave arrivals on 15 closely spaced refraction profiles reveals a significant, systematic, and symmetric dependence of average layer 2 velocities on their distance to the north and south of the Hawaiian ridge. Beyond the flexural arch surrounding the ridge the velocity‐depth solutions indicate a normal layer 2. Within the arch (approximately 155 km from the ridge) the average elastic velocities in layer 2 are lowered by 0.8–0.9 ± 0.2 km/s. Within 75 km of the ridge the average velocities are again normal. Elastic and elastic‐plastic flexural models for the regional compensation of the Hawaiian islands predict tensional stress drops of 0.8 kbar in the upper lithosphere for the region having lowered velocities in layer 2, which are similar in magnitude with laboratory measurements of the confining pressure drop necessary to reduce velocities in porous basalts by 0.5 km/s. A significant inverse relationship (correlation coefficient of 0.818) exists between the average elastic velocities in the upper 1.0 km of the igneous crust and the strain in the upper crust calculated from these flexural models. The correlation between lowered average velocities in layer 2 and increased tensional stresses and strains suggest that crack opening in the upper crust accompanies the flexure. These observations are the first reported for a midplate load and corroborate previous suggestions from seismic and flexural data at subduction zones.