Patent GB-914359-A (GB)
Title: Method of and apparatus for correcting a plurality of seismic signals
Inventor: WOODS JOHN PRICE
IPC: G01V1/30
Filed: 1960-02-01
Abstract: 914,359. Geophysical prospecting. ATLANTIC REFINING CO. Feb. 1, 1960, No. 3511/60. Class 40 (7). [Also in Group XXXVIII] A method for preparing corrected seismic records which comprise a plurality of seismic signals, recorded on a seismic field record in terms of a function of amplitude versus travel time, to compensate for travel time errors resulting in characteristic features of these signals appearing on the field record at elapsed time points which differ from the true travel time of these signals to those characteristic features, comprises the steps of establishing an arbitrary time scale proportional to the true travel time of the signals; detecting a first of those signals whilst concomitantly developing a total correction voltage and using the correction voltage to change the points along the field record at which each incremental portion of this signal is detected by amounts equal to predetermined travel time errors, the total correction voltage including a varying D.C. voltage component which is a function of variable travel time error and at least one D.C. voltage component which is a function of fixed travel time error; recording the detected signal at substantially the instant of detection as a function of amplitude versus a function of the arbitrary time scale; and repeating this procedure for each of the other seismic signals whereby a record of these signals is produced whereon their characteristic features appear at points representative of true travel time. In the embodiment of Fig. 1, a drum 4 driven at a preselected constant speed by a motor 10 carries a field record on a carrier 6 and a plotting sheet on a carrier 8, an arm 28 carries an electromagnetic pick-up 30, a recording device 18 is provided above carrier 8 and a generator 40 producing an electric signal proportional to predetermined travel time errors feeds a translator 42 which converts that signal into arcuate motion of arm 28. Function generator 34 produces dynamic-error correction signals and is directly coupled to the shaft of aluminium drum 4. Unit 36 produces a voltage for setting the zero of the seismic section record and unit 38 produces a constant voltage proportional to the static-error correction for each trace on the field record magnetic tape. Unit 24 feeds a signal to electromechanical translator 22 to slide detector and recorder carriers 26, 18 respectively along rigid bars 12, 14, after each field record trace has been processed. To cater for shorter field record tapes a third section may be added to the drum. The field record may be of any other known type, e.g. variable width or density on transparent film; and similarly for the seismic section record. The position of arm 28 is monitored by visual display 32. Recorder 18 may be decoupled from lateral drive bar 20 to afford manual traverse. Function generator 34 may be a potentiometer, or a device which reads out digital values on punched tape, or a curve follower following a curve traced in conductive ink. Sequence switches for automatic re-recording of field record traces are actuated by pulses initiated by drum 4, a pulse following single or multiple drum revolution, Fig. 2 (not shown).