A converted-wave experiment in Uganda

J. Helen Isaac, Francesca Martini, Gary F. Margrave

We processed an experimental 3C survey acquired in Uganda. There was concern that the azimuths of the 3C geophones were not exactly as planned, which was magnetic north, since the geophones had been dropped into holes. The results of rotation analysis on the data were inconsistent and we considered that they deviated too much from the planned field orientation to be used. We rotated the data using a constant receiver orientation of magnetic north.

The PS data image the acoustic basement well but reflections shallower in the section have less continuity and are of lower amplitude. The PP data show more structure on the basement reflector and much better resolution of reflectors above basement. We picked two horizons on the migrated PP and PS sections by correlating first the basement reflectors then picking a shallower horizon on the PS data and matching that to the PP data. The values of Vp/Vs were consistent with Vp/Vs values of 3.0 - 3.4 measured on logs from a nearby well.