Apparatus for and methods of seismic prospecting
First Claim
1. A method of seismic prospection wherein the subterranean response from a single generated impulse is recorded into two channels the first channel providing datum information, i.e., a signal corresponding to said impulse, and the second channel providing signals corresponding to reflections of said impulse, wherein the played back second channel signals are re-recorded in a continuation of the second channel, and the played back impulse signal from the first channel is used to initiate said re-recording and switch into a continuation of the first channel a continuous tone which is recorded as a tone burst simultaneously with the re-recording of the second channel signals, and wherein the re-recorded second channel signals are played back with the tone burst and visual tracings are made from the played back re-recorded second channel signals over the period of said burst, each play back being made at an equal or slower speed than the associated recording.
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Abstract
In seismic prospecting a local response is achieved by striking a hammer on the ground, and the recording apparatus is arranged to be triggered by the hammer to run from a short time before the impulse to a predetermined time after it. The impulse is recorded into one channel and the reflections into another, and the latter are slowed down by successive recordings to a speed where they can be mechanically plotted. The impulse signal in the other channel is used as a timing and control signal for the re-recording and playbacks.
9 Citations
16 Claims
- 1. A method of seismic prospection wherein the subterranean response from a single generated impulse is recorded into two channels the first channel providing datum information, i.e., a signal corresponding to said impulse, and the second channel providing signals corresponding to reflections of said impulse, wherein the played back second channel signals are re-recorded in a continuation of the second channel, and the played back impulse signal from the first channel is used to initiate said re-recording and switch into a continuation of the first channel a continuous tone which is recorded as a tone burst simultaneously with the re-recording of the second channel signals, and wherein the re-recorded second channel signals are played back with the tone burst and visual tracings are made from the played back re-recorded second channel signals over the period of said burst, each play back being made at an equal or slower speed than the associated recording.
- 9. Apparatus for processing a subterranean seismic response including impulse and reflection signals, comprising a first two-channel tape recorder, a second two-channel tape recorder, each of which can record at one speed and play back at a slower speed, a continuous frequency generator, first means for switching on said first recorder to record said impulse and reflection signals on respective channels, second means responsive to the playback of the impulse signal in the first channel of the first recorder for switching on said second recorder to record on both channels and to switch into the first channel of said second recorder the output of said continuous frequency generator, the second channel of the second recorder serving for the recording of played back signals from the second channel of the first recorder, and means for forming visual traces from the played back second channel output of the second recorder responsive to the first channel output of that recorder to be operative while said continuous frequency obtains.
Specification