IMPROVED HIGH-RESOLUTION SEISMIC PROFILING.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF GEOLOGY AND GEOPHYSICS
Pagination or Media Count:
High repetition-rate seismic reflection profiling is a technique used at sea to obtain visual analogues of geologic cross-sections. The thesis reports the development of a high resolution profiling system which was field-tested in Boston Harbor. The system incorates several improvements over conventional apparatus. Visual display of the profiles is produced from playback of magnetic tape-recordings. A tape-recording is used to trigger the sweep and to modulate the beam of a cathode-ray tube successive traces are recorded across slowly-moving 35 mm. film. Electronic sweep control and optical stacking onto photographic emulsion allow greater flexibility and dynamic range than the mechanical sweep stacking on electro-sensitive paper employed by pre-existing facsimile recorders. Edgertons boomer sound source was modified to eliminate cavitation and to give non-oscillatory acoustic pulses of 118 decibels peak pressure relative to 1 dynesq cm at 1 meter. The initial impulse 0.1 millisecond long is followed by a slow decay which provides low-frequency energy for deeper penetration. Author
- Geology, Geochemistry and Mineralogy