<Tr> <Td> 3.87 </Td> <Td> 9.5 metric tons </Td> <Td> 40 GJ </Td> <Td> Explosion at Chernobyl nuclear power plant, 1986 </Td> </Tr> <Tr> <Td> 3.91 </Td> <Td> 11 metric tons </Td> <Td> 46 GJ </Td> <Td> Massive Ordnance Air Blast bomb </Td> </Tr> <Tr> <Td> 6.0 </Td> <Td> 15 kilotons </Td> <Td> 63 TJ </Td> <Td> Approximate yield of the Little Boy atomic bomb dropped on Hiroshima (~ 16 kt) </Td> </Tr> <Tr> <Td> 7.9 </Td> <Td> 10.7 megatons </Td> <Td> 45 PJ </Td> <Td> Tunguska event </Td> </Tr>

Who developed the richter scale and how does it work