Abstract
The three-dimensional propagation directions of earthquake waves near ground surface were estimated for eight earthquakes. Travel times of the incidence and reflected waves were obtained by using the Normalized Input-Output Minimization (NIOM) method, and 3-D angles of propagation directions were estimated. The estimated directions correlated well with the theoretical ones calculated from the epicenter coordinates, focal depth, and the velocity distribution in the earth's crust. However, the estimated angles (0-20 degrees) from the vertical axis for the observed waves were somewhat larger than the theoretical ones (0-4 degrees).
