Crustal model of the Bransfield Rift, West Antarctica, from detailed OBS refraction experiments

• Published in: Geophysical Journal International
• Main Authors: Grad, M., Shiobara, H., Janik, T., Guterch, A., Shimamura, H.
• Format: Text
• Language: English
• Published: Oxford University Press 1997
• Subjects: Articles; Antarctic; The Antarctic; West Antarctica; Bransfield Strait; Bridgeman; Bransfield Trough; Antarc*; Antarctica
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/130/2/506; https://doi.org/10.1111/j.1365-246X.1997.tb05665.x

The first detailed deep seismic refraction study in the Bransfield Strait, West Antarctica, using sensitive OBSs (ocean bottom seismographs) was carried out successfully during the Antarctic summer of 1990/1991. The experiment focused on the deep crustal structure beneath the axis of the Bransfield Rift. Seismic profile DSS-20 was located exactly in the Bransfield Trough, which is suspected to be a young rift system. Along the profile, five OBSs were deployed at spacings of 50-70 km. 51 shots were fired along the 310 km profile. This paper gives the first presentation of the results. A detailed model of the crustal structure was obtained by modelling the observed traveltimes and amplitudes using a 2-D ray-tracing technique. The uppermost (sedimentary?) cover, with velocities of 2.0-5.5 km s−1, reaches a depth of up to 8 km. Below this, a complex with velocities of 6.4-6.8 km s−1 is observed. The presence of a high-velocity body, with V p =7.3-7.7 km s−1, was detected in the 14-32 km depth range in the central part of the profile. These inhomogeneities can be interpreted as a stage of back-arc spreading and stretching of the continental crust, coinciding with the Deception-Bridgeman volcanic line. Velocities of 8.1 km s−1, characteristic of the Moho, are observed along the profile at a depth of 30-32 km.