Microseisms recorded at Berkeley

The cause and nature of microseisms have been the subject of much study since the beginning of instrumental seismology. As yet, however, there is no uniformity of opinion on either the nature of the movement or the cause. The periods of microseisms vary from a fraction of a second to a minute or more, and the amplitudes are frequently many microns. There is one class of microseisms with a period‐range of four to ten seconds that is recorded all over the world on seismographs with appreciable magnification for motions of these periods. Only microseisms of this class will be considered in this discussion.