Exploration Geophysics - Volume 5, Issue 1, 1974

A continuous offshore resistivity method has been designed for use in shallow, multi-method, marine geophysical surveys. This inexpensive system employs towed electrodes near the sea surface and is compatible with other ship-board equipment.

Limited field testing indicates that the offshore resistivity results obtained, after processing to assess the influence of bottom topography, contain useful information on lateral sub-bottom resistivity contrasts which may be of geological significance.

Further testing and development of the method appears to be warranted as it should not only provide additional data on sub-bottom material but could be extremely useful in studying the conductive overburden problem often encountered in galvanic surveys on land.

The performance of an automatic magnetic interpretation technique with regard to the accuracy of depth and width estimation has been studied using statistical techniques and theoretically generated anomalies over semi-infinite magnetized dykes. The automatic interpretation was based on the method of Koulomzine et al. Geophysics Vol. 35.

This study revealed that the method produces generally reliable depth estimates over a wide range of geologically realistic models but the absolute accuracy of both depth and width estimates vary considerably and appear to be dependent on the actual depth-to-width ratio of the dyke.

The automatic interpretation procedure was also found to provide more accurate estimates of depth and width when the original anomaly was asymmetrical as opposed to symmetrical.