HR: 11:10h
AN: S52A-03    [Abstracts]
TI: Long-offset detection of offshore airguns by onshore broadband seismographs
AU: * Zhou, H
EM: hzhou@uh.edu
AF: U of Houston, Dept of Geosciences, Houston, TX 77204-5007 United States
AU: Li, A
EM: Aibing.Li@mail.uh.edu
AF: U of Houston, Dept of Geosciences, Houston, TX 77204-5007 United States
AU: Zhao, B
EM: bo.zhao@mail.uh.edu
AF: U of Houston, Dept of Geosciences, Houston, TX 77204-5007 United States
AU: Warren, A
EM: awarren@reservoirgeophysical.com
AF: Reservoir Geophysical, 13313 SW Frwy, Suite 285, Sugar Land, TX 77478 United States
AB: In aseismic areas such as the coastal regions of the Gulf of Mexico, using onshore seismographs to detect signals from airgun sources during oil industry offshore seismic surveys offers a great potential to yield a large amount of long-offset data. The feasibility of onshore seismographs to detect marine airgun sources has been demonstrated by the LARSE surveys in southern California and the SIGHT survey in New Zealand. These surveys used a 8470-inch3 airgun array of the R/V Maurice Ewing. However, a much smaller airgun array volume, about 3400 inch3 or less, is typically used in today's industry marine reflection surveys. It is also foreseeable that, to minimize the impact on marine life and environment, future airgun surveys will use even smaller volumes. Therefore, we have started a pilot project to assess the detectability of the small-volume airgun signals in the Gulf of Mexico using portable onshore broadband seismographs. This research project is collaboration between seismologists at the University of Houston and the Reservoir Geophysical Corporation, who is providing airgun source information during their field tests of a 2000-inch3 airgun array. The source area is between West Cameron and South Timbalier in the Gulf of Mexico, offshore of Louisiana. So far we have conducted a series of numerical analyses of the detectability of the airgun signal. The calculation suggests that the soft ocean-bottom sediments of our study area should be very effective to transmit the airgun energy through the ocean floor to the onshore stations. During the next several months, we will carry out several field experiments by placing broadband seismographs at different onshore locations during the airgun surveys. We hope to show the detectability of the airgun signal in terms of source-station offset distance, station site condition, signal frequency content, source water depth, and ocean bottom hardness. Because we will have all necessary information about source timing, location, site conditions and acquisition parameters, we should be able to conduct source stacks to improve the S/N ratio.
DE: 3025 Marine seismics (0935)
DE: 3094 Instruments and techniques
DE: 7203 Body wave propagation
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2005 Joint Assembly