Microseisms 8
Microseisms 8 :
Continuous ground motion constituting the background noise for any seismic measurement. Microseisms with frequencies higher than about 1 Hz are usually caused by artificial sources, such as traffic and machinery, and are sometimes called microtremors, to be distinguished from longer-period microseisms due to natural disturbances. At a typical station in the interior of a continent, the microseisms have predominant periods of about 6 seconds. They are caused by surf pounding on steep coastlines and the pressure from standing ocean waves, which may be formed by waves traveling in opposite directions in the source region of a storm or near the coast (LonguetHiggins, 1950). Also called double frequency microseism and marine microseism. See Chapter 4 in this Manual, Webb (2002), Kulhanek (2002); also Aki and Richards (2002 or 2009), p. 616-617)
