High-Resolution Seismic-Reflection Data from Offshore of Northern California—Bolinas to Sea Ranch

Data Acquisition and Processing

Data were acquired on cruise S-08-09-NC in September 2009. Information on this cruise is available at http://cmgds.marine.usgs.gov/fan_info.php?fan=S809NC. Using a SIG 2mille minisparker source, ~1,150 km of seismic-reflection profiles were collected at ~1,000-m line spacing.

The SIG 2mille minisparker system uses a 500-Joule, high-voltage electrical discharge that was fired at intervals ranging from 0.50–0.75 seconds depending on water depth. The source signal frequency bandwidth ranges from 200–1600 Hz. Half-second intervals were used where water depth was less than 350 m, which characterizes most of the study area. The 0.50-second firing rate and normal survey speeds of 4–4.5 nautical miles per hour yield a data trace about every meter. The data were recorded on a 15-m-long hydrophone streamer in standard SEG-Y 32-bit floating-point format, using Triton Subbottom Logger (SBL) software that merges seismic-reflection data with differential global positioning system (GPS) navigation data. After the survey, ship-heave statics were calculated using SIOSEIS seismic processing software, and these corrections were applied to the data to filter out the effect of the sea swell. A short-window (20 ms) automatic gain control algorithm and a 160–1,200-Hz bandpass filter was applied to the minisparker data. Data quality varies with substrate, with penetration ranging up to as much as 200–300 m in inferred fine-grained sediments.

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