We analyze three-dimensional (3D) particle motions of crack waves which propagate along a fracture to determine fracture orientation. Crack waves were measured at an artificial subsurface fracture at a depth of approximately 370 m in the Higashihachimantai Hot Dry Rock model field in Japan. Dispersion was observed in crack waves. Velocities of crack waves below 100 Hz are 100 m/s-150 m/s along this artificial fracture. Therefore, crack waves arrived after compressional wave and shear wave. A coherence matrix is used to analyze the 3D particle motions in the frequency domain. Noise, which is outside of the band of the detector, is excluded in the coherence matrix analysis. We examine the polarization of 3D particle motions of crack waves using Principal Component Analysis. The longest axis of an ellipsoid which approximates the 3D particle motions shows a direction consistent with estimates obtained by core-sample measurements and tectonic stress measurements. The differences in fracture orientation obtained from the crack-wave analysis and the core sample analysis are less than 16¿ in azimuth and less than 20¿ in dip. ¿ American Geophysical Union 1996