Earth tremor

Yesterday at about 1700 hours there was an earth tremour. It is not recorded on the Instituto Geografico Nacional which means it must have been less than 1.5 on the richter scale. Nevertheless to experience it is a little disturbing. That is until you look at the Instituto's website. There are maps which show where these earth tremors occur. The main map is covered with tiny dots, each one representing a tremor event. There are hundreds of dots.