Abstract
The present observations and analyses were made as a continuation of the study on“Noise Attenuation in Shallow Holes (I)”(T. HIRONO, S. SINEHIRO, M. FURUTAa nd K. KOIDE,1968). The test s ite was moved to the Onahama Weather Station on the Pacific Coast of Northeastern Japan, where the seismicity is high. The magnification of seismographs at the station, however, is limited only to 100 around a period of 1 sec owing to high background noise.
The instrumentation and method of analyses were basically the same as in the previous study. In the present study, more efforts were made to study the reduction of amplitudes of earthquakes in depth to discuss the change of the signal to noise ratio (StoNratio)with depth in detail.
