The correct option is It relates to the energy released during the quake..
Explanation
Earthquakes are measured based on two primary attributes: Magnitude and Intensity. These are quantified using distinct scales that assess either the energy released at the source or the severity of shaking felt at a specific location.
- It measures the intensity of the earthquake. is incorrect: The intensity of an earthquake is measured by the Mercalli Scale. Intensity describes the severity of the earthquake in terms of its effects on the land surface, humans, and structures.
- It is expressed in numbers 1-12. is incorrect: The Mercalli Scale is expressed in a range of numbers from 1 to 12. In contrast, the Richter Scale is logarithmic and does not have a fixed upper limit (though practically it rarely exceeds 9.5).
- It relates to the energy released during the quake. is correct: The Richter Scale measures the magnitude of an earthquake. Magnitude relates directly to the energy released during the quake at the focus (hypocenter). It is calculated based on the amplitude of the seismic waves recorded by seismographs.
- It is based on the visible damage caused. is incorrect: Visible damage and destruction are the parameters used to determine intensity on the Mercalli Scale. The Richter Scale is an objective instrumental measurement independent of the visible destruction caused.
Key Takeaway: The Richter Scale quantifies Magnitude (energy released), while the Mercalli Scale quantifies Intensity (visible damage and impact).