Calibration function of local magnitude for different regions in China

The statistical analysis method of the magnitude residuals is used to calculate the deviation and standard deviation of local magnitudes for single station based on the seismic observation data from all the 31 provincial seismological networks of China during 1973—2002. The local magnitude calibration functions are established in Northeast-North China, South China, Southwest China, Qinghai-Xizang and Xinjiang regions, and their usage ranges are defined. The local magnitude determination results in practice show that the standard deviations of local magnitude become smaller by using the new calibration functions than the current ones of short-period instrument, suggesting that the new calibration functions can raise the measurement accuracy of local magnitude.