Abstract
We propose a method to estimate phase velocities of the Rayleigh and Love waves using array observation records of three-component microtremors. Previous researchers have provided a method on the basis of the spatial auto-correlation (SPAC) method, assuming that the Rayleigh and Love waves are propagated in the same direction. However, this assumption seems to be poorly suited to microtremors, because of the various possible sources and the uncertain nature of microtremors. Thus, we formulate the SPAC coefficients for microtremors in a case where the Rayleigh and Love waves are propagated in different directions. From this, it is shown analytically that the phase velocities of surface waves can be calculated from the SPAC coefficients and that they are independent of the propagation directions of the surface waves.
