James Freeman Gilbert

James Freeman Gilbert (born August 9, 1931 in Vincennes, Indiana; † August 15, 2014 in Portland, Oregon) was a US geophysicist.

Gilbert studied at the Massachusetts Institute of Technology, where he received his bachelor's degree in 1953 and his doctorate in geophysics in 1956. He then went to the University of California, Los Angeles (UCLA), where he became Assistant Professor in 1957 and Associate Professor in 1960. In 1960/61 he was a research geophysicist at Texas Instruments. From 1961 he was Professor at the University of California, San Diego, and at the Institute of Geophysics and Planetary Physics (IGPP) of the Scripps Institution of Oceanography, of which he was Associate Director from 1976 to 1988. He has been Professor Emeritus there since 2001. In 1987 he was a Fairchild Scholar at Caltech, in 1973 a Visiting Professor in Utrecht (Veining-Meinesz Institute for Geophysics), and in 1964/65 and 1972/73 a Guggenheim Fellow at the University of Cambridge.

Gilbert was one of the discoverers of the Earth's free vibrational modes, which he found with Adam Dziewoński from analysis of data from the 1964 Alaska earthquake and later the 1970 Columbia earthquake. At about the same time, Frank Press and Maurice Ewing also succeeded. To do this, he developed the Backus-Gilbert method of inversion of seismic data with George Edward Backus. In the early 1970s, he was involved in the installation of a worldwide network of seismometers for the study of the Earth's interior, the IDA Array (Project IDA, International Deployment of Accelerometers), the first 40 stations of which went into operation in 1974.

In 1981 he received the Gold Medal of the Royal Astronomical Society, in 1999 the William Bowie Medal, in 1990 the Balzan Prize, in 1985 the Arthur L. Day Medal of the Geological Society of America, and in 2004 the Medal of the Seismological Society of America. He held honorary doctorates from Utrecht University and the Colorado School of Mines. He was a member of the National Academy of Sciences and the American Academy of Arts and Sciences (1961).

He had been married since 1959 and had three children.