Which statement describes the Mercalli scale? 1 This scale measures seismic waves based on their size. 2 This scale rates an earthquake according to how much damage it causes. 3 This scale produces a single rating for earthquakes that reach the surface. 4 This scale measures the magnitude of an earthquake based on the size of seismic waves.
The Correct Answer and Explanation is:
Correct Answer: 2 – This scale rates an earthquake according to how much damage it causes.
The Mercalli Intensity Scale is a qualitative scale used to assess the intensity of an earthquake based on its observed effects on people, buildings, and the Earth’s surface. Unlike other scales that measure the energy or magnitude of an earthquake using scientific instruments (like the Richter or moment magnitude scales), the Mercalli scale is based on human observations and reports of damage.
Developed by Giuseppe Mercalli in the early 20th century and later modified, the Mercalli scale uses Roman numerals from I to XII. A rating of I means the earthquake was not felt by people and caused no damage, while a rating of XII indicates total destruction, with buildings collapsing and ground features being significantly altered.
This scale is especially useful in populated areas where the physical effects of the quake can be readily observed. For instance, if windows rattle and people are awakened from sleep, the intensity might be around IV or V. If buildings collapse and the ground cracks open, the intensity may be IX or higher.
However, the Mercalli scale has some limitations. Because it relies on subjective human reports and visible damage, the same earthquake can have different Mercalli ratings depending on local geology, building construction, and population density. An earthquake in a rural area with few structures might have a lower observed intensity than the same quake in a densely populated city.
In summary, Statement 2 is correct because the Mercalli scale is focused on the observable impact and damage caused by an earthquake, rather than its underlying energy or seismic wave amplitude.
