An earthquake which occurred with 2.0 magnitude or less are called micro-earthquakes and generally, this earthquake is not realized by people. Commonly, this earthquake is recorded on local seismographs.
Earthquakes with magnitude of 4.5 or greater can be recorded by sensitive seismographs all over the world. There are thousand such shocks annually happen.
The energy released at the source of the earthquake as determined from measurements on seismographs. An earthquake consists only one magnitude. This magnitud scale most commonly in use how is called thermoment magnitude scae.