Transcript of oral history interview conducted in 1990 of Professor Leon Knopoff (1925-2011), internationally renowned scientist, professor of physics and geophysics, and research musicologist, at UCLA from 1950 to 2011. Known for his mathematical formulations of earthquake dynamics and for measuring seismic waves and gravity variations around the globe, he was noted also for his exceptional teaching and generous international collaboration. The 1964 representation theorem by Robert Burridge and Leon Knopoff is recognized as the first principle in modern seismology.Parents, childhood in Los Angeles, science vs music career. Attended LA City College and Caltech. Graduate student at Caltech. William Smythe, other Caltech professors. First academic post at Miami University, Ohio. Summer research position at UCLA Institute of Geophysics. Return to UCLA Inst. of Geophysics as Louis Slichter's postdoc. David Griggs. First important published papers 1954. Graduate students Adrian de Hoop, Anthony Gangi, Walter Pilant, Robert Fredricks, Joseph Hook, Edgar Kraut, Lawrence Porter. Gordon MacDonald. Freeman Gilbert. Knopoff's change of focus from theoretical seismology. The increasing divergence of geophysics and seismology from physics and mathematics. Joint appointments of UCLA Inst. of Geophysics faculty with other UCLA departments. Sabbatical leave in Cambridge, England,1960-61. Frank Press. Program of regional studies with long-period seismometers around the Alps and around the Mediterranean. The inverse problem of geophysics. Marriage to Joanne Van Cleef 1961. NSF Earth Science Panel 1959. The three major parts of Knopoff's career: theoretical seismology, surface waves, earthquake clustering and seismicity. George Kennedy and thermoluminescence. Archaeological expedition to Jordan and gravity profile of Dead Sea Rift. Recruitment to Caltech faculty and research at Caltech. Return to UCLA after one-year leave. Academic involvement in music. Sabbatical leave in Karlsruhe, Germany, 1966. Stephan Mueller, synthetic seismology. IUGG. Secretary General of Upper Mantle Project. Pembroke Hart. AFOSR, Vela Program. Soviet Union. Vladimir Keilis-Borok. Knopoff's father and uncle. Siege of Leningrad. Committee on Mathematical Geophysics. Soviet mathematicians. Historical and Soviet anti-Semitism. Continental drift, convection, V. Beloussov. Willard Libby, second director of UCLA Inst. of Geophysics. Fusion of UCLA Departments of Geophysics and of Geology into the Department of Earth and Space Sciences. New directions of the Inst. of Geophysics under Knopoff's directorship. Charles Kennel, William Schopf. Earthquake prediction: national program, Knopoff’s research and point of view. Linear vs non-linear processes, the hope that physics departments will become interested in these non-linear problems.