Figure 8: VSP seismograms collected at Hole 735B using a 1000 cubic inch airgun and a vertical component geophone. Depths in the borehole are given in meters below the seafloor; no sediments were found at Site 735. The seismograms were filtered to pass energy less than 250Hz; signal-to-noise ratios are 5-15dB in the 5-90Hz band. The small, upward deflection at about 25ms after the first arrival is an out-of-plane reflection - possibly from the hull of the drilling ship. The data have been corrected for gain changes and spherical attenuation, so the decay in amplitude with borehole depth is due solely to attenuation. The loss of high frequency energy in the initial 50ms over just 350m (less than a wavelength at 10Hz) can clearly be seen. [Swift et al., 1991; Swift and Stephen, 1992]


Retun to the 2003 Fall AGU Poster

THIRD PARTY BOREHOLE SEISMIC EXPERIMENTS DURING THE OCEAN DRILLING PROGRAM

Created on December 10, 2003 by Tom Bolmer