Mild Earthquake Last Night

I was busy blogging and watching tele at the same time when i experienced a mild shake of the  house.  It was like somebody was jumping and pushing the house to possibly make it shake like that.  I can not ask any one because i was alone and hubby was not home at the moment.  So, i did not mind what happened.  Then i saw wall status popping up in Facebook saying that they also felt the earthquake.  This is the second time in my four years stay in Netherlands to actually experienced a mild earthquake.  According to the KNMI, the earthquake had a magnitude of 3.1 and was referred as a natural quake that is normally caused by gas.