Abstract
The authors performed the observation of microtremors in 201 sites widly distributed in Nagoya City to research dynamic properties of surface soil layers and reinforced concrete structures. The measurements were carried out by using a seismometer of moving coil type with period of 1 second. Observed data were analyzed not only instrumentally by means of an autocorrelator, but also by means of the degital computor. The results of the present research are summarized as follows : (1) The predominant periods of the ground primarily depend on the characteristics of surface soil layers, and are capable of being an effective basis for the ground classification. The maximum amplitudes of microtremors also depend on the characteristics of surface soil layers. (2) The zoning maps of Nagoya City showing the ground classification and the contour lines for predominant periods are presented. (3) The relationship between the damage rates of wooden buildings due to the Tohnankai earthquake and the dynamic properties of microtremors is discussed based on the results of measurements, and the fact is confirmed that the selective resonance of the ground and the buildings is important as a cause of earthquake damage. (4) The damping factors as well as the natural periods of the ground and the reinforced concrete structures are obtained from the results of microtremors observation.
