Abstract: In this paper, the authors discussed the problem of how to create a continuous M_L mag nitudesy stem in regional seismic network during the transitional process from analogous observation system to full digital observation system. They used the determined seismic parameters obtained from tens of seismic records of Fujian and Taiwan region from Fujian regional digital seismic network, and records from the same station by both digital and analog ousseismo graphs synchronously. It was emphasized that the application of the emulation technique of digital seismic signal in determining seismic basic parameters, especially in determining M_L magnitude by using broad-band velocity-type digital seismograph so as to generate a “ seamless” regional seismic catalog. The statistical results show that using approximate emulate method to convert the waveform of JCV-100 short- period velocity-type digital records into that of DD-1 short -period displacement -type analog records, the statistical error of M_L magnitudes between the two system could be less than ± 0. 1 magnitude unit. If the strict emulation would be further made, including correction of instrument response and emulation of waveform and amplitude, then the error rang e could be reduced further so that a continuous M_L magnitudesy stem could be created in the regional seismic network.

Key words: Regional digital seismic network, M_L magnitude system transition, Digital seismic signal emulation, Transfer function of seismograph