A comparative study on Hi-net velocity differential and KiK-net acceleration

This paper introduces the configuration and data format of Hi-net and KiK-net constructed and operated by National Research Institute for Earth Science and Disaster Prevention of Japan. In order to analyze the uncertainty of velocity differential in both amplitude and spectrum, we study the distribution of natural logarithm of peak acceleration ratio and natural logarithm of acceleration response spectrum ratio between Hi-net velocity differential and KiK-net observed acceleration, as well as the ratios above in relation to magnitude and focal distance, using the data recorded by both Hi-net and KiK-net from 282 M_j≥5.0 earthquakes with focal depth less than 100 km. It turns out that the differential of digital velocity record is different from the observed acceleration in both amplitude and spectrum, so the former can not be directly treated as acceleration. Since the distribution of the two ratios mentioned above show some regular pattern, dividing peak acceleration or response spectrum at given period by some coefficient can reduce the uncertainty resulting from numerical differentiation of digital velocity record. Besides, the uncertainty can also be described in the way of probability.