Inge Lehmann (1888–1993)

Inge Lehmann grew up with the field of seismology, becoming a pioneer among women and scientists. Born in Denmark, on May 13, 1888, her early education came in Denmark at a coeducational school run by the aunt of Niels Bohr. It was a place where boys and girls studied the same subjects, where all played soccer and rugby and learned needlepoint. In 1920 she earned her master’s degree in mathematics after 12 years of undergraduate and graduate studies at the University of Copenhagen and University of Cambridge, studies that were interrupted by 6 years of full-time actuarial work. In later years, she would study in Germany, France, Belgium, and Netherlands; in 1928 she earned a second master’s degree, in geodesy, from the University of Copenhagen. Lehmann’s career in seismology began in 1925 when she aided N. E. Norlund as he established seismic networks first in Denmark, then in Greenland. By 1928, Lehmann was named the first chief of the seismology department of the newly established Royal Danish Geodetic Institute, a position she held for 25 years. She recorded, analyzed, and cataloged seismograms from Denmark and Greenland, published seismic bulletins, and worked as the “only Danish seismologist,” as she once described herself. In 1936 she published the paper that sealed her place in the history of geophysics. Known simply as “P’ (P-prime),” the paper suggested a new discontinuity in the seismic structure of the Earth, now known as the Lehmann discontinuity, a region that divides the core into inner and outer parts. Using ray theory and travel time curves to interpret seismograms, Lehmann discovered that the P’ phase of seismic waves traveling through the inner Earth was not the result of diffraction, the commonly held interpretation at the time, but a clear indication of an inner core. Later, Lehmann established herself as an authority on the structure of the upper mantle. Extended parts of her later years were spent as a visiting scientist at the Lamont-Doherty Earth Observatory, Dominion Observatory, the Seismological Laboratory at Caltech, and the University of California, at Berkeley. She also led her colleagues as a founder and president of the European Seismological Federation, president of the Danish Geophysical Society, and vice president of the International Association of Seismology and Physics of the Earth’s Interior. In 1971, Inge Lehmann was presented with the William Bowie Medal, the American Geophysical Union’s highest honor, which is granted to a scientist who has made fundamental contributions to the study of geophysics and who has lived up to the AGU ideal of unselfish cooperation in research. Lehmann also was named an AGU Fellow and was awarded honorary doctorates from Columbia University and the University of Copenhagen. —Michael Carlowicz American Geophysical Union Washington, D.C.