SUPWS - Phase stack or phase-weighted stack (PWS) of adjacent traces  
         having the same key header word                               

 supws <stdin >stdout [optional parameters]                            

 Required parameters:                                                  
    none                                                               

 Optional parameters:                                                  
    key=cdp           key header word to stack on                      
    pwr=1.0           raise phase stack to power pwr                   
    dt=(from header)  time sampling intervall in seconds               
    sl=0.0            window length in seconds used for smoothing      
                      of the phase stack (weights)                     
    ps=0              0 = output is PWS, 1 = output is phase stack     
    verbose=0         1 = echo additional information                  

 Note:                                                                 
    Phase weighted stacking is a tool for efficient incoherent noise   
    reduction. An amplitude-unbiased coherency measure is designed     
    based on the instantaneous phase, which is used to weight the      
    samples of an ordinary, linear stack. The result is called the     
    phase-weighted stack (PWS) and is cleaned from incoherent noise.   
    PWS thus permits detection of weak but coherent arrivals.          

    The phase-stack (coherency measure) has values between 0 and 1.    

    Output traces get the headers from the first trace of each data    
    ensemble to stack, including the offset field. Use "sushw
    afterwards, if this is not acceptable.                             


 
 Author: Nils Maercklin, 
         GeoForschungsZentrum (GFZ) Potsdam, Germany, 2001.
         E-mail: nils@gfz-potsdam.de

 References:
    B. L. N. Kennett, 2000: Stacking three-component seismograms.
       Geophysical Journal International, vol. 141, p. 263-269.
    M. Schimmel and H. Paulssen, 1997: Noise reduction and detection
       of weak , coherent signals through phase-weighted stacks.
       Geophysical Journal International, vol. 130, p. 497-505.
    M. T. Taner, A. F. Koehler, and R. E. Sheriff, 1979: Complex
       seismic trace analysis. Geophysics, vol. 44, p. 1041-1063.

 Trace header fields accessed: ns
 Trace header fields modified: nhs