Abstract
The ground is always vibrating from the natural and artificial disturbances, it is called a microtremor which measures a few microns in amplitude.
It has been clarified by engineering seismologists that there was a very closed relationship between the earthquake damages and the subsurface structures, and that when the ground was visited by earthquake shocks, the predominant period of the earthquake motion nearly coincides with one of the frequent periods of the microtremor at the respective places.
From the multireflection theory, the microtremor comprises the wave motions magnified by complex multireflection and transmission of the wave within the surface soft layer. Therefore we can estimate the subsurface structures by studying the microtremor.
In this paper, the author reports the results of some theoretical and practical studies on the sounding with the microtremor data and discusses them.
