TONS OF COLLAPSING ROCK killed five gold miners, injured five others and left two missing in a shaft more than a mile beneath the earth's surface, authorities in Johannesburg, South Africa, said Friday. A small tremor shook loose several tons of rock Thursday in a shaft of the Doornfontein mine, a spokeswoman said . . . AN EARTHQUAKE with a preliminary reading of 5.0 on the Richter scale shook an area along Japan's western coast Friday, but there were no immediate reports of damage or casualties, the Central Meteorological Agency said.