[SAC-HELP] ppk rel help

[George Helffrich]

Dear Jeremy -

On 6 Mar 2012, at 19:37, Jeremy Pesicek wrote:

> sac helpers please help me
> 
> I have two questions:
> 
> 1)  why is the behavior of the commands 'p1 rel' and 'ppk rel' different?  I can line up waveforms on a pick nicely using 'p1 rel', but when I use 'ppk rel', the same waves align on something different, on b I think.  I found a previous post about this same issue back on July 5, 2006, but could not find a response to it.  I want to make picks after aligning the waves on another pick.

PPK parses 'relative' and 'absolute' but does not do anything different based on that option.  For a pick window with multiple files, it always chooses as a time anchor the zero time in the first file and calculates a time window forward and backward from that which includes the data in all the rest of the files.  You might  design a pick strategy based on that behavior.

          George Helffrich
          george.helffrich at bris.ac.uk