Question

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

Answer 1

It depends on various parameters... for example, assume your house built over a clay type or soil type crust, which has more damping power or absorption power for any change in their position...

and yeah, all earthquakes cannot be sensed by us because of our relative lack of senses... millipedes can detect earthquakes as same applies for dogs...

It depends. on. you.