Developments and applications of modern airborne electromagnetic surveys : proceedings of the U.S. Geological Survey Workshop on Developments and Applications of Modern Airborne Electromagnetic Surveys, October 7-9, 1987

Abstract

Front Cover: Past and present U.S. Geological Survey aircraft used for geophysical surveys are depicted flying over terrain typical of the foothills west of Denver, Colorado. The aircraft, in order of age (from left to right), are Beech Model 17, Staggerwing; Douglas DC-3; Convair CV-240; and Fairchild Porter PC 6/C-H2.Cover design by Art Isom, U.S. Geological Survey. Developments and Applications of Modern Airborne Electromagnetic SurveysEdited by DAVID V. FITIERMAN Proceedings of the U.S. Geological Survey Workshop on Developments and Applications of Modern Airborne Electromagnetic Surveys, October 7-9, 1987 U.S. GEOLOGICAL SURVEY BULLETIN 1925 DEDICATIONFrank C. Frischknecht, a geophysicist with the U.S. Geological Survey and a pioneer in the field of airborne geophysics, was killed August 12, 1987, in a helicopterplane collision near Ketchikan, Alaska.Frank was born in Bicknell, Utah. He received a Bachelor of Science degree in Electrical Engineering (1950) and a Master of Science degree in Geophysics (1953) from the University of Utah. He continued his education at the University of Colorado, earning a second Master of Science degree in Geophysical Mathematics (1967) and a Doctor of Philosophy (1973) in Electrical Engineering Physics.Frank's professional career with the U.S. Geological Survey spanned more than 35 years, beginning in 1952 with work on airborne geophysical instrumentation, data compilation, and interpretation problems. From 1955 to 1962, he developed a variety of controlled-and natural-source electromagnetic techniques that were applied to numerous geological problems. In 1962, the U.S. Geological Survey acquired a Convair 240 aircraft and Frank became involved in developing, acquiring, and testing geophysical instrumentation for airborne surveys. Of particular interest to him were a new INPUT electromagnetic system and an automated magnetometer system.His accumulated experience resulted in the now classic textbook "Electrical Methods in Geophysical Prospecting," published in 1966 in collaboration with George V. Keller. In 1967, Frank published the first computer-generated, layered-earth theoretical electromagnetic sounding curves that became the basis for most early airborne electromagnetic interpretational methods. During this same period, Frank also developed a scalemodel electromagnetic test facility that provided data crucial to understanding field observations and testing interpretational methods. His model results are internationally recognized as standards against which numerical results are checked. He developed an airborne very low frequency (VLF) receiver incorporating an electric field reference that enabled it to produce resistivity maps used for geologic mapping. He oversaw initial development and construction of the first airborne power-line receiver, which has since been successfully used to produce resi.stivity maps with greater depth of exploration that is possible with VLF systems. At the time of his death, Frank had completed and was working on chapters on elec...