Using overlapping sonobuoy data from the Ross Sea to construct a 2D deep crustal velocity model
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ORIGINAL RESEARCH PAPER
Using overlapping sonobuoy data from the Ross Sea to construct a 2D deep crustal velocity model M. M. Selvans • R. W. Clayton • J. M. Stock R. Granot
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Received: 13 June 2011 / Accepted: 1 December 2011 / Published online: 20 December 2011 Ó Springer Science+Business Media B.V. 2011
Abstract Sonobuoys provide an alternative to using long streamers while conducting multi-channel seismic (MCS) studies, in order to provide deeper velocity control. We present analysis and modeling techniques for interpreting the sonobuoy data and illustrate the method with ten overlapping sonobuoys collected in the Ross Sea, offshore from Antarctica. We demonstrate the importance of using the MCS data to correct for ocean currents and changes in ship navigation, which is required before using standard methods for obtaining a 1D velocity profile from each sonobuoy. We verify our 1D velocity models using acoustic finite-difference (FD) modeling and by performing depth migration on the data, and demonstrate the usefulness of FD modeling for tying interval velocities to the shallow crust imaged using MCS data. Finally, we show how overlapping sonobuoys along an MCS line can be used to construct a 2D velocity model of the crust. The velocity model reveals a thin crust (5.5 ± 0.4 km) at the boundary between the Adare and Northern Basins, and implies that the crustal structure of the Northern Basin may be more similar to that of the oceanic crust in the Adare Basin than to the stretched continental crust further south in the Ross Sea. M. M. Selvans R. W. Clayton J. M. Stock Seismological Laboratory, California Institute of Technology, 1200 E. California Blvd., MC 252-21, Pasadena, CA 91125, USA M. M. Selvans (&) Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, MRC 315, Washington, DC 20560, USA e-mail: [email protected] R. Granot Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
Keywords Sonobuoy Multi-channel seismic Ross Sea Finite-difference 2D velocity model Crustal structure
Introduction Using sonobuoys to investigate deep crustal structure Sonobuoys provide a means of obtaining long offsets for deep velocity analysis while conducting multi-channel seismic (MCS) studies. They are preferable to using a long streamer in locations with difficult open water conditions, such as in the Ross Sea and Southern Ocean, where research cruises regularly encounter sea ice, icebergs, and intense storms. Ocean-bottom seismometers (OBS) provide another method for collecting active seismic data with large offsets, but are more expensive than sonobuoys and are challenging to recover in the conditions described above. Sonobuoys are also an ideal method for collecting large offset seismic data in other settings where ship navigation is constrained, such as locations with ship traffic and narrow bodies of water such as fjords. Marine refraction seismology has long been recognized as an essential technique for
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