ABSTRACT
The standard approach to calculate the wave travel times between two recording points have been either to use the time difference for a characteristic peak in the signal, or to determine the time lag where the cross-correlation of the signals has a maximum. In structures, the waves attenuate due to damping and this changes the shape (i.e., the phase) of the waves. The phase shifts in two records are caused by the combined effects of wave travel times, plus the phase distortions due to damping (Safak and Cakti, 2009). The phase shifts introduced by damping can be eliminated by calculating the time shifts from the envelopes of the signals, rather than the original signals. The envelope functions are not affected by the dispersive properties of the medium (Safak and Cakti, 2009).
