Figure 5. Photograph of NOAA Ship RUDE. Click on figure for larger image.

Sidescan-sonar and bathymetric data were collected aboard the NOAA Ship RUDE in 2004 (fig. 5). A Klein 5500 towfish (455 kHz) acquired sidescan-sonar data, which were recorded using Triton ISIS software and archived in extended Triton format (xtf). Sidescan-sonar data were processed using USGS software packages XSonar and ShowImage (Danforth, 1997). A median filtering routine was applied to the sidescan-sonar data to remove speckle noise. Sonar data were further processed to correct for slant-range and radiometric distortion inherent in the sonar data and corrected for towfish layback. Sonar data were mosaicked using XSonar, resulting in an enhanced, geographically correct, sidescan-sonar mosaic with 1 meter/pixel resolution.

An Odom Echotrac DF3200 MKII dual-beam echo sounder operating at 24 and 200 kHz acquired sounding data aboard the NOAA Ship RUDE. In areas of interest, shallow-water multibeam echo-sounder data were acquired with a Reson SeaBat 8125 operating at 455 kHz. Bathymetric data were processed using CARIS HIPS/SIPS software. Sounding and multibeam data were used with IVS Fledermaus software to create a bathymetric surface with full coverage of the study area and 45-m resolution, which eliminated gaps between track lines.

About 580 km of seismic-reflection data with 1- to 2-m resolution were collected by USGS in 1980 aboard the R/V NEECHO using an EG&G Uniboom seismic system that filtered to a 400 to 4000 Hz bandpass and that recorded at a quarter-second sweep rate (Needell and others, 1983a, b).