SUDIVSTACK -  Diversity Stacking using either average power or peak   
               power within windows                                    


 Required parameters:                                                  
    none                                                               

 Optional parameters:                                                  
    key=tracf        key header word to stack on                       
    winlen=0.064     window length in seconds.                         
                     typical choices: 0.064, 0.128, 0.256,             
                                      0.512, 1.024, 2.048, 4.096       
                     if not specified the entire trace is used         

    peak=1           peak power option default is average power        

 Notes:                                                                
    Diversity stacking is a noise reduction technique used in the      
    summation of duplicate data. Each trace is scaled by the inverse   
    of its average power prior to stacking.  The composite trace is    
    then renormalized by dividing by the sum of the scalers used.      

    This program stacks adjacent traces having the same key header     
    word, which can be specified by the key parameter. The default     
    is "tracf" (trace number within field record).                   
    For more information on key header words, type "sukeyword -o".   

 Examples:                                                             
    For duplicate field shot records:                                  
        susort < field.data tracf | sudivstack > stack.data            
    For CDP ordered data:                                              
        sudivstack < cdp.data key=cdp > stack.data                     


 
 Author: Mary Palen-Murphy,
         Masters' candidate, Colorado School of Mines,
         Geophysics Department, 1994

 Implementation of "key=" option: Nils Maercklin,
         GeoForschungsZentrum (GFZ) Potsdam, Germany, 2002.

 References:

    Embree, P.,1968, Diversity seismic record stacking method and system:
        U.S. patent 3,398,396.
    Gimlin, D. R., and Smith, J. W., 1980, A comparison of seismic trace 
        summing techniques: Geophysics, vol. 45, pages 1017-1041.

 Trace header fields accessed: ns, dt, key=keyword
 Trace header fields modified: tracl