He joined the Seismological Laboratory in 1924 and received his Ph.D. from the California Institute of Technology in 1935.
He is best remembered for his work in charting the location of deep earthquakes in the Pacific Ocean. After graduating from Pomona College in 1921, Benioff began his career with the idea of being an astronomer and worked for a time at Mount Wilson Observatory, but when he found that astronomers work at night and sleep in the daytime, he quickly switched to seismology. Benioff is considered a genius in the design of earthquake instruments.
One of his first instruments, created in 1932, was the Benioff seismograph, which senses the movement of the earth - these instruments are now used in every country in the world. Equally famous is the Benioff strain instrument, which records the stretching of the Earth's surface. Benioff noticed that earthquake sources get deeper under the overriding tectonic plate proceeding away from the trench at a subduction zone.
He realized that this inclined array of earthquake sources indicate the position of the portion of the plate that has already been subducted. Thus, that pattern of earthquakes is known as a Wadati-Benioff zone. From the early 1930s, Benioff also worked on creating electric musical instruments.
In particular a piano, violin and cello. He continued developing these instruments for the rest of his life, working for over two decades with pianist Rosalyn Tureck and also, towards the end of his life with the Baldwin Piano Company.
Fellow American Academy of Arts Science, American Association for the Advancement of Science, Geological Society American. Member National Academy Science, American Physical Society, Acoustical Society American, American Geophysical Union, Seismological Society American, Royal Astronomical Society, Phi Beta Kappa. Patentee seismographs.
Married Alice Silverman, February 27, 1928.; married second, Mildred Lent, October 31, 1953. Children: Paul, Dagmar (Mistress E. Friedman), Elena (Mistress E. G. Jackson, Junior.