5. Not all earthquakes are felt by people; however, such earthquakes are often detected on seismographs. Why?

Question

compassionate · Answer

Because a lot of earthquakes happen deep within the layer because the earth is constantly grinding against itself. In order for an earthquake to happen and be felt by people, it would have to occur by the cracking of tectonic plates or the sliding of the surface. The aforementioned things must occur more toward the surface of Earth.

anonymous · Answer

thank you so much!!! :)

compassionate · Answer

If I may add furthermore, seismographs are very sensitive and can pick up low frequency  vibrations and movements deep within the earth, whereas humans, do not possess the sensitivity to feel such events.