IMPROVED HIGH-RESOLUTION SEISMIC PROFILING.
Abstract
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. Edgerton's boomer sound source was modified to eliminate cavitation and to give non-oscillatory acoustic pulses of 118 decibels peak pressure (relative to 1 dyne/sq 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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1966
- Accession Number
- AD0639199
Entities
People
- Donald J. Krotser
Organizations
- Massachusetts Institute of Technology