High-resolution chirp seismic-reflection data collected offshore Oceanside, southern California during field activity 2017-686-FA from 2017-10-23 to 2017-10-31

The chirp seismic-reflection profiles were acquired with a swept frequency source towed at 4 to 11 meters depth below the sea surface and fired at roughly every 1 to 2 meters, depending on water depth. Data were recorded to Edgetech JSF format using Edgetech recording software. Survey speeds were approximately 4.5 knots.

Chirp seismic-reflection data were first converted from JSF to SEG-Y format. The SEG-Y files were then processed using Echos by Paradigm Geophysical. The following processing steps were applied to each line: 1)The fish depth header word was read and converted from millimeters to two-way travel time to create a fish-depth static value; 2) The fish depth static was applied to the data to correct for changing tow depth of Chirp fish; 3) an additional a Paradigm Echos smoothing module was applied to the data to correct for the motion of the sea; and 4) final processed SEG-Y was output with correct navigation written to header bytes 81 and 85 in UTM zone 11N coordinates with a scalar value of 1. The scalar value located in header byte 71 only applies to arcsecond values in headers bytes 73 and 77. These data are divided up and presented by navigation line, as reflected in the individual file names.