is an allpass wavelet. To estimate n0, we can apply the method explained in the last section to P(Z). Figure shows an example with the same field data as in Figure . We see that two factors of this factorization process have similar frequency content. As expected, the traveltimes picked by two methods are equal. Because the phase spectrum of an allpass filter is always a nondecreasing function, the procedure for unwrapping the phase of P(Z) is easier than that for S(Z).
Figure 4 The top panel shows the same trace as one in Figure . The middle and bottom panel show the minimum phase and allpass parts of this wavelet, respectively. The vertical dashed lines indicate the picking positions. The fat, dashed curve superposed on the curve of the top panel is the signal reconstructed from two factorized parts.