German–American geologist (1889–1960)
Gutenberg was educated at the Technical University in his native city of Darmstadt and at the University of Göttingen, where he obtained his PhD in 1911. He then taught at the University of Freiburg becoming professor of geophysics in 1926. He emigrated to America in 1930, taking a post at the California Institute of Technology, and later served as director of the seismological laboratory (1947–58).
In 1913 Gutenberg suggested a structure of the Earth that would explain the data on earthquake waves. It was known that there were two main types of waves: primary (P) waves, which are longitudinal compression waves, and secondary (S) waves, which are transverse shear waves. On the opposite side of the Earth to an earthquake, in an area known as the shadow zone, no S waves are recorded and the P waves, although they do appear, are of smaller amplitudes and occur later than would be expected. Gutenberg proposed that the Earth's core, first identified by Richard Oldham in 1906, is liquid, which would explain the absence of S waves as, being transverse, they cannot be transmitted through liquids. Making detailed calculations he was able to show that the core ends at a depth of about 1800 miles (2900 km) below the Earth's surface where it forms a marked discontinuity, now known as the Gutenberg discontinuity, with the overlying mantle. Its existence has been confirmed by later work including precise measurements made after underground nuclear explosions.
In collaboration with Charles Richter, Gutenberg produced a major study, On Seismic Waves (1934–39), in which, using large quantities of seismic data, they were able to calculate average velocity distributions for the whole of the Earth.
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