In seismology, a microseism is defined as a faint earth tremor caused by natural phenomena. The term is most commonly used to refer to the dominant background seismic noise signal on Earth, which are mostly composed of Rayleigh waves and caused by water waves in the oceans and lakes. Thus a microseism is a small and long-continuing oscillation of the ground.

Read more about Microseism:  Detection and Characteristics, Generation of 'secondary' Microseisms, Form of Rayleigh Waves Modified By The Ocean Layer: Free Waves and Forced Waves, See Also