Abstract

This report gives a summary of the field program and instrumentation used on the R/V Gyre in the Gulf of Mexico in May, 2003, to collect multichannel seismic data in support of USGS and Department of Energy gas hydrate studies. Tabulated statistics, metadata, figures and maps are included to show the breadth of data collected and preliminary interpretations made during the field program. Geophysical data collected during this cruise will be released in a separate report.

At the start of the cruise, three test lines were run to compare different source configurations in order to optimize data quality for the objectives of the cruise. The source chosen was the 13/13 in³ Generator-Injector (GI) Gun. Following these tests, a total of 101 lines (approximately 1033 km) of 24-channel high-resolution seismic reflection data were collected in the northern Gulf of Mexico. 59 lines (about 600 km) were collected in and around lease block Keathley Canyon 195. An additional 4 lines (85 km) provided a seismic tie between the Keathley Canyon data and USGS multichannel data collected in 1999. About 253 km of data were collected along 35 short lines in and around lease block Atwater Valley 14 on the floor of the Mississippi Canyon. Three lines (53 km) completed the cruise and provided a seismic tie to USGS multichannel data collected in 1998.

Two on-board trained marine-mammal observers fulfilled the requirements determined by NOAA/National Marine Fisheries Service to avoid incidental harassment of marine mammals as established in the Marine Mammal Protection Act (MMPA). A total of three species of dolphins were observed during the cruise and one basking shark. No sperm whales were sighted. During the cruise, seismic operations were not delayed or terminated because of marine mammal activity.