SEISMIC HOLOGRAPHY

• US 3,629,796 A
• Filed: 12/11/1968
• Issued: 12/21/1971
• Est. Priority Date: 12/11/1968
• Status: Expired due to Term

• Current Assignee: Emmet D. Riggs, Eugene R. Brownscombe, William M. Campbell
• Original Assignee: Emmet D. Riggs, Eugene R. Brownscombe, William M. Campbell
• Inventors: Brownscombe, Eugene R., Campbell, William M., Riggs, Emmet D.
• Application Number:
  US04/782,965
• Time in Patent Office: 1,105 Days
• US Class Current: 367/9
• CPC Class Codes: G01V 1/003 Seismic data acquisition in general, e.g. survey design G01V1/3808, G01V1/42 take precedence
• CPC Class Codes: G01V 1/34 Displaying seismic recordings or visualisation of seismic data or attributes
• CPC Class Codes: G03H 3/00 Holographic processes or apparatus using ultrasonic, sonic or infrasonic waves for obtaining holograms; Processes or apparatus for obtaining an optical image from them G03H1/22 takes precedence; acoustic non-destructive testing using holographic methods G01N29/0663; seismology using acoustic vibrations G01V1/00; non-holographic methods for visualizing acoustic waves G10K15/00
• CPC Class Codes: Y10S 359/901 Acoustic holography

Abstract

Apparatus and processes for seismic holography with emphasis on field procedures, recording methods, and interpretation processes. Coherent acoustical energy is transmitted into the earth and received with areal detector means. The received signals are mixed with a reference signal so that interference signals are obtained. The interference signals are recorded as spot exposures on photographic film or plates. After arranging the exposures in proper order and scaling, the resulting hologram is illuminated with coherent light. Subsurface structure is indicated by comparing pairs of holograms by observing their images. Holographic images can be combined in several ways to give a difference image which indicates change in subsurface structure.

Claims

1. A process for seismic holography comprising a. transmitting coherent acoustical energy into the earth at a first surface location, b. receiving seismic signals with areal detector means at a plurality of detector locations remote from said first location, c. obtaining a reference signal by detecting transmitted acoustical energy at a point adjacent said first location, d. selectively time delaying said reference signal with respect to each seismic signal with which it is to be combined in order to achieve maximum interference, e. amplifying said reference signal to a predetermined level relative to each seismic signal to accomplish field of depth focusing, f. combining each of said seismic signals with the reference signal as modified in steps (d) and (e) to produce a plurality of corresponding interference signals, g. modulating the illuminous intensity of a point source of light with each of said interference signals, h. forming a photographic record of the light output resulting from the modulations such that a plurality of spot exposures are formed having the same geometrical relation as the detector locations where the seismic signals were derived, i. scaling said photographic record in order to reduce it to dimensions compatible for reconstruction at optical wavelengths, and j. illuminating the hologram thus obtained with coherent light so that a holographic image is formed of the earth'"'"''"'"'s subsurface.