Velocities of P and S waves for drilling core rocks at Syowa Station, Antarctica

概要

論文の詳細を見る
Velocities of compressional and shear waves for the drilling core samples at Syowa Station, East Antarctica are measured at confining pressure up to 0.5 GPa (5 kbar). The samples consist predominantly of granitic complex or gneiss being older than 350-533m.y. in the shield region. The P-wave velocities for three orthogonal directions and the S-wave velocities for two orthogonal directions are measured to reveal anisotropy of the rocks. The velocities increase rapidly with increasing pressure at low pressures below 50-120 MPa due to crack closure. Whereas, the velocities increase linearly with increasing pressure at higher pressures than 50-120 MPa, and the velocities for each direction are nearly the same. A velocity model in the upper 20km of the crust is estimated from the laboratory data, assuming an appropriate temperature profile. The proposed model of P-wave velocity increasing gradually with depth is consistent with the upper crustal structure obtained by the explosion seismic experiments in the Ongul Islands and the Mizuho Plateau, East Antarctica.
国立極地研究所の論文