Richard Dixon Oldham FRS (; 31 July 1858 – 15 July 1936) was a British geologist who made the first clear identification of the separate arrivals of P-waves, S-waves and surface waves on seismograms and the first clear evidence that the Earth has a central core.
Life
Born on 31 July 1858 to Thomas Oldham, a Fellow of the Royal Society and geologist, Oldham was educated at Rugby School and the Royal School of Mines.
In 1879 Oldham became an assistant-superintendent with the Geological Survey of India, working in the Himalayas. He wrote about 40 publications for the Survey on geological subjects including hot springs, the geology of the Son Valley and the structure of the Himalayas and the Ganges plain. His most famous work was in seismology. His report on the 1897 Assam earthquake went far beyond reports of previous earthquakes. It included a description of the Chedrang fault, with uplift up to 35 feet and reported accelerations of the ground that had exceeded the Earth's gravitational acceleration. He also included accounts of earth-waves that could be seen travelling across the plain, and of waterspouts. Oldham was not the first to suggest that the earth had a dense core, but he provided the first direct evidence of its existence and size.
In 1903, Oldham resigned from the GSI due to ill-health and returned to the United Kingdom, living in Kew and various parts of Wales. and from 1920 to 1922 served as the President of the Geological Society of London. Later in his life he became interested in the geography and history of the Rhône delta. He died on 15 July 1936.