Post-stack migration processing of all MCS reflection data was done at the USGS WHMSC, and was primarily performed using OpenCPS software (version 3.3.0). Data were imported into OpenCPS from SEG-Y files, and processed through a standard sequence of trace editing, common-midpoint (CMP) sorting, bandpass filtering, deconvolution, velocity analysis, normal moveout correction, stretch muting, stacking, and post-stack time migration. Streamer geometry (true group and source locations) were applied from the P190 navigation files provided by the Langseth staff. Trace headers in these SEG-Y data include CMP number (bytes 20-22), Number of samples in a trace (bytes 115-116), Sample interval (bytes 116-117), Source Coordinates (bytes 72-74, bytes 76-78), Group Coordinates (bytes 80-82, bytes 84-86), and Trace Positions (bytes 180-182, bytes 184-186). A scalar for the geoposition is set in bytes 71-71. All coordinates are written in UTM19N, EPSG code 32619. A full text header is written to include all of the processing information:
Description: Post-stack phase shift time migration to 200 Hz using auto-picked velocities guided by a 1D velocity function hung between picked water-bottom,basement, and Moho.
Prestack gains: Spherical divergence
Poststack gains: None
Band: 6-200 Hz
Cruise:MGL1407
Line:MGL1407MCS01
Coordinate projection:WGS84/UTM 19N
ESPG:32619
WKT:"+proj=utm +zone=19 +datum=WGS84 +units=m +no_defs"
Files were written to SEG-Y format from within OpenCPS.
Nathan C. Miller performed this and all subsequent process steps.