Passive seismic imaging, the process of synthesizing active surface
data by correlating ambient noise records,  has languished
in the realm of theory since the original
concept was presented 1968.  Very few experimental tests
have been fielded since then, and none provided convincing 
results.  The recent surge in interest in the idea has generated a
substantial literature that has proved the validity of the theory
beyond the initial conjecture, as well as experimentally at the lab
scale and the global scale.  This thesis makes a substantive
contribution to the field by extending the processing algorithms
available for passive seismic data and by analyzing a real 3d data
volume from a 2300 station areal array.
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Direct migration of transmission wavefields, introduced herein, is a
robust, convenient processing method.  Any conventional shot profile
migration algorithm that maintains separate up-coming and down-going
wavefields can be easily modified to use passive data.  The only
change required is to use the data for the initial condition of the
source wavefield.  Processing passive data by direct migration can
provide substantial computational savings.  This is especially true if
multiple images are produced from the total volume of data collected.  However,
synthesized shot gathers may be required for velocity analysis or
addressing common data problems such as noise removal or aliasing.
\par
Over 35~hours of passive data collected at the Valhall development in the 
North Sea was processed to produce synthesized shot gathers and migrated
images.  The synthesized shot gathers did not provide any subsurface
information.  Instead, they were dominated by a direct arrival through the 
water column from the gas flare at a production facility 40~km away from 
the array.  The energy from the gas flare is a coherent noise source
that arrives at the array at such a shallow angle that it is confined
to the water column and does not refract into the subsurface.  As a
coherent noise source, the energy manufactures events in image results
that are not subsurface reflectors.  Removing the far-field noise from
the synthesized gathers also removes the interpretable, though false,
events from images.
