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Supws - Noise reduction and detection of weak, coherent arrivals via 
        phase-weighted stacks

To run the demo, type "Supws" on the commandline of a terminal window (without
the quotes). 

Relevant selfdocs: susynlv, sustack, sudivstack, supws


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 shell script generates the same shot gather as the demo script for diversity
stacking ("$CWPROOT/src/demos/Diversity_Stacking/Sudivstack") via "susynlv". 
Random noise with different signal-to-noise ratios is added to several copies 
of this shot gather (via "suaddnoise"). After sorting the traces by tracf 
("susort), an equally-weighted stack ("sustack") is compared to a diversity 
stack ("sudivstack") and to a phase-weighted stack ("supws"). 

The default output is X window graphics. You may switch to PostScript output
by setting the flag "POSTSCRIPT=1" at the top of the script "Supws".



References (phase-weighted stacks):

Kennett, B. L. N., 2000: Stacking three-component seismograms.
    Geophysical Journal International, vol. 141, p. 263-269.
Schimmel, M. and Paulssen, H. 1997: Noise reduction and detection
    of weak , coherent signals through phase-weighted stacks.
    Geophysical Journal International, vol. 130, p. 497-505.



Nils Maercklin
GeoForschungsZentrum (GFZ) Potsdam
Telegrafenberg E 352
D-14473 Potsdam, Germany
[e-mail]