Scripts within SIOSEIS (version 2013.1.1) and Seismic Unix (version 4.2) were used to process SEG-Y data, create navigation files, and plot images. The processing flow and scripts used to produce navigation files including trackline shapefiles are summarized below and in the following processing steps.
1. SIOSEIS (version 2013.1.1) was used to read SEG-Y files, renumber shots starting from one, extract the envelope-detected trace, and write out new SEG-Y files. The original shot numbers, which were assigned by SonarWiz sequentially over the duration of an acquisition session despite SEG-Y file changes, are preserved in the raw SEG-Y data.
2. The SIOSEIS script Sio_medianstk applied a two-trace median stack (trim 50 percent of the values furthest from the median amplitude) to improve subsequent water bottom picking.
3. The SIOSEIS script siothresh_pltwbt was used to pick the water-bottom time from the median stacked SEG-Y files, apply a swell filter to smooth water-bottom time picks and shift the trace data by the difference between the smoothed and unsmoothed water bottom time before writing the shifted trace data to a new SEG-Y file.
4. The Seismic Unix script Plot512i_s creates a swell-filtered PNG image of the seismic profile using supsimage and ImageMagick (version 6.6.1). The resultant images are 29 inches high and contain an 80 millisecond (two-way travel time) window of data. Images show two-way travel time (seconds) along the y-axis (left margin) and distance along profile (in 500 shot intervals, corresponding to the point features in the shapefile 2014-009-FA_512i_500sht.shp) on the x-axis (along top of profile).
