Here's why:

* Microquakes are earthquakes with magnitudes less than 3.0 on the Richter scale. They are too small to be felt by humans, but they can be detected by sensitive instruments.

* Earthquakes are caused by the movement of tectonic plates, which are large pieces of the Earth's crust.

* Microquakes can occur along plate boundaries, where plates are moving past each other, or within plates themselves.

While "microquakes" is the most accurate term, you might also see "earth tremors" or "minor earthquakes" used to describe these small shifts.