A 2-C method to obtain the fast principal direction and time lag between the slow and fast principal time series. Illustrated are the cross correlograms between the two recorded components as they are rotated in 5 increments from -90 degrees to 90 degrees (horizontal axis). The vertical axis is the time lag, with a zero time lag corresponding to a value of 4 s on the plot. When the geophone axes are aligned with the principal directions, the waveform should display a maximum similarity (although they will be time shifted). The correct angle and time lag is give by the largest correlation value. As with the Alford rotation there is an ambiguity since there are multiple maxima. The maxima should be identified and the (angle, time lag) pair that yields the fast waveform leading the slow waveform is the correct choice.