| Date | Text | |
|---|---|---|
15 Jul 1936
Richard Dixon Oldham |
death Richard Dixon Oldham Died 15 Jul 1936 at age 77 (born 31 Jul 1858). Irish geologist and seismologist who discovered evidence for the existence of the Earth's liquid core (1906). In studying seismograms of great 1897 Indian Earthquake he identified P (primary) and S (secondary) waves. It is interesting that he did not get a clue to the presence of the core from the S waves, which are actually incapable of being transmitted through the liquid of the outer core. (The liquid core does not transmit the shear wave energy released during an earthquake.) Rather he noted the existence of a shadow zone in which P waves from an earthquake in the opposite hemisphere of the earth failed to appear. |
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