Harold Sears

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Harold Sears
Harold Sears headshot.png
Latest company Hall Sears Inc
BSc Electronics and Instrumentation
BSc university Southwestern College in Winfield Kansas


Harold A. (Hal) Sears was known for producing geophysical instrumentation, particularly geophones for exploration seismic recording.

Biography Citation for the Reginald Fessenden Award

Contributed by E. M. Hall

Harold A. (Hal) Sears was born September 14, 1903 at Fall River, Kansas. He attended public schools at Eureka, Kansas and college at Southwestern College in Winfield Kansas. His interest in electronics and instrumentation began early, and in 1920, Hal became a licensed radio operator. During the ensuing years, he worked in various capacities as a radio operator and technician aboard ship and on shore.

In 1930, Hal joined Western Air Express, Alhambra, California. This company, the forerunner of TransWorld Airlines, was engaged in the establishment of a transcontinental radio communications system for its aircraft, under the direction of Herbert Hoover, Jr. After completion of the development stage of the project, Hal was transferred to Tulsa, Oklahoma.

In 1934, Hal resigned from TWA and began his 49-year geophysical career when he started to work for Seismograph Service Corporation in Tulsa. At SSC, he worked as an observer on a field crew and as a technician in SSC's Tulsa lab. In 1935, Hal left SSC's Tulsa lab and went to work for Barnsdall Oil Company. It was at Barnsdall that Hal made his first geophone, a product for which he later became famous.

Hal built his first geophones while working on a Barnsdall field crew in Louisiana. These first geophones were patterned after the variable reluctant geophones of SSC. As the crew moved from town to town, Hal packed his equipment and moved with them, renting space and setting up anew every time the crew moved. He later helped Barnsdall set up their geophysical laboratory in Houston and moved his work from the field to the lab.

When Barnsdall closed the lab in 1940, Hal purchased the shop equipment and continued his development of geophones. It was this endeavor that led to Hal's forming Electro-Technical Labs (ETL), where he began manufacturing geophones for sale. His first major product was an oil damped, moving magnet geophone, and his customers were such respected contracting companies as General Geophysical and Rogers-Ray, the predecessor company to Rogers Exploration and Robert H. Ray.

In the late nineteen forties and early nineteen fifties, major geophone users began expressing a strong interest in the use of multiple geophones. Hal was impressed by discussions with friends such as C. H. (Chili) Carlisle and Dr. Tom Poulter concerning ground stacking, filtering, and enhanced coupling benefits available from geophone rays. However, the size, cost, and delicate nature of geophones then currently available severely restricted their use in large numbers. In response to the need for a small size, low cost, and extremely rugged geophone, Hal worked with W. P. (Pete) Johnson to develop ETL's model EVS geophone. The EVS was a moving coil, electromagnetically damped geophone. Because of its revolutionary small size and relatively low cost, the EVS made the use of multiple geophones a practical reality. It was Dr. Poulter who first suggested to Hal that geophones be connected in strings of nine geophones, connected three by three series parallel. Hal used such strings to conduct numerous field tests with Humble in West Texas and, shortly thereafter, with Phillips. As a result of these and other such tests, Humble and Phillips became big customers for the EVS, and by the mid-fifties, the use of multiple geophones had become widespread in all areas where record quality was a problem.

With the advent of tape recording. Hal acquired for ETL an exclusive license to manufacture and sell a pulse-width tape recording system developed by the Carter Oil Laboratory. To provide the financial resources, necessary to carry out this program, he sold his controlling interest in ETS in late 1955.

In 1957, Hal formed Hall-Sears, Inc. and continued his pioneering in geophone development. The Hall-Sears HS-1 was the first small geophone utilizing dual coils, such dual coils being required today in all geophones in order to meet the low distortion requirements of digital recording systems. The HS-1 holds the distinction of the longest tenure of any geophone ever developed that is still being manufactured today, 26 years after its introduction. Under Hal's leadership, Hall-Sears also developed the first small size, low cost earthquake geophone, the HS-10. This geophone became a standard for universities and research institutions, and remains today as the most widely used geophone in the one-to-two-hertz frequency range.

The explosive surge in the use of large numbers of geophones in the early nineteen sixties led to the development of the HS-J geophone. Of all the geophones introduced by Hal, the HS-J perhaps made more friends than any other. It was the smallest geophone ever used, lightweight, inexpensive, and practically indestructible. Its acceptance was so widespread that a market survey conducted in 1966 indicated that more than 70% of all crews operating in the free world were using the HS-J. The increase in size of the total geophone market has since permitted other geophone models to surpass the HS-J in total numbers, but none have reached its market penetration or acceptance.

Hal has truly been the leader in developing and manufacturing geophones for the geophysical industry. His input is clearly evident when the history of today's geophone suppliers is reviewed. The geophone operations of Geosource, Geo Space, and Litton are continuations of ETL, Hall-Sears, and Walker-Hall-Sears, respectively, all of which were founded by Hal. In addition, the other two major suppliers, Mark Products and Sensor Netherlands (now owned by Geosource) were formed by principals who began their geophone careers and gained their first geophone experience while working for Hal. No other person has made a contribution comparable to Hal's in the development of geophones, this essential but often underrated basic sensor used in data acquisition. He is clearly the "Father of Geophones," as used today.

Many of Hal's friends also remember his contributions to the Houston Geophysical Club, later the Geo Center. During its approximate ten years of existence, he was the driving force behind its operation, dedicating relentless effort to its cause, at a substantial personal sacrifice in time and money. Few people, if any, have a greater liking for the geophysics industry than Hal, and I am sure all those who know Hal join me in endorsing his selection for this outstanding award.