High-resolution, chirp seismic-reflection data collected offshore Oceanside to San Diego, southern California, during field activity 2018-638-FA from 2018-05-21 to 2018-05-26

The chirp seismic-reflection profiles were acquired with a swept frequency source towed at about 5 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 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 coordinates. The scalar value for bytes 73 and 77, located in header byte 71 is incorrect, and the correct value is 1000. Delay value in header byte 109 has not been applied and should be applied for accurate display. These data are divided up and presented by navigation line, as reflected in the individual file names.