MCS Survey

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MCS Survey

During the Voltaire cruise, 1111.1 km of MCS data were acquired, for a total of 132.6 hours of active shooting. The Voltaire lines are shown in Fig. 23s. In Fig. 24 is presented one oh the MCS lines acquired, time migrated by means of Disco/Focus Paradigm Inc. software and displayed by means of WinPics Divestco Inc. software.

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**Figure 23:** work areas and MCS track lines for cruise V2002.
$\includegraphics{MCS-tracks.eps.conv}$

During the cruise we performed quality control on the shooting interval for MCS which is the critical parameter defining the geometry. The software installed on board allowed to shoot at the constant spacing of 50 m. To perform this the time interval was varied to account for differences in the ship velocity. Using the navigation files the program nav01.f extracts the relevant information for the shots and outputs a label file used for gmt plotting. The same navigation file is explored by vnafdkm.f program to output a navdiff.dat file where we have in different columns the time interval between shots, the distance interval and the average ship velocity between shots estimated from the previous 2 values.

As the shooting time is recorded only to the second, a small fluctuation is observed in the time interval (and consequently a corresponding variation in velocity) that is not real, but due only to rounding. As it can be seen by the example shown in Fig. 25, Fig. 26 and Fig. 27 (prepared by the navdiff.csh script) we obtained a very stable shooting interval and the differences in velocity were well compensated by symmetrical differences in the shot time interval. Compared to other recent academic MCS surveys we must stress that the VOLTAIRE shooting system performed extremely well.

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**Figure 24:** time migration of MCS line VOL02, displayed by WinPics.
$\includegraphics[scale=1]{VOL02.eps.conv}$

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**Figure 25:** quality control on MCS shooting acquisition, based on shot point interval.
$\includegraphics[scale=0.62]{navdiff-s.eps.conv}$

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**Figure 26:** quality control on MCS shooting acquisition, based on time interval.
$\includegraphics[scale=0.62]{navdiff-t.eps.conv}$

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**Figure 27:** quality control on MCS shooting acquisition, based on velocity measurements.
$\includegraphics[scale=0.62]{navdiff-v.eps.conv}$

Next: Quality control on bathymetry Up: RESULTS Previous: CHIRP survey and Coring Contents

2003-01-21