Microtremor is a low amplitude (in the order of micrometres) ambient vibration of the ground caused by man-made or atmospheric disturbances.
Observation of microtremors can give useful information on dynamic properties of the site such as predominant period and amplitude.
[1] More detailed information on the shear wave velocity profile of the site can be obtained from microtremor array observation.
The major drawback of the method proposed by Kannai and Tanaka [2] was that they considered the Fourier spectra of observed horizontal motions to reflect the transfer function of the surface.
Yukta Nakamura[1] in 1989, modified microtremor analysis by proposing a new technique, generally referred to as the H/V method.