In a marine geophysical survey, every attempt is made to maintain the streamer at a constant optimum depth. But there are issues involved in selecting that optimum depth; too shallow, and the record tends to be noisy; too deep, and a ghost notch appears in the useful bandwidth of the seismic signal.

Geothermal energy is becoming an increasingly hot topic. Recent research suggests that even areas outside ‘high-temperature fields’ may be sufficiently warm to generate electricity.