The correct answers are - Richter and Mercalli.
The Richter scale and the Mercalli scale, are the two scales for measuring the strength of the earthquakes that are the most widely accepted throughout the world.
On the Richter scale, there's numbers from 0 to 9, with 0 being no earthquake, and 9 being the strongest earthquake.
The Mercalli scale has numbers from 0 to 12, with 0 being no earthquake, while 12 being the strongest earthquake. The Mercalli scale is a bit more detailed than the Richter scale.
