Abstract:This paper used a template matching technique to detect missing earthquakes of the Qilian, Qinghai MS5.2 earthquake that occurred on November 23, 2015. In existing catalogs, aftershock sequence data, especially from the short time after the main shock, are usually huge so we detected continual waveforms one day after the mainshock. In that day, the seismic network recorded 62 aftershocks, including single-station earthquakes. In this study, we chose 30 ML>1.0 aftershocks as the templates, and finally found 31 missing earthquakes after detection, which was about 0.5 times the number given by the network catalog. According to the linear fitting relationship between frequency envelope difference amplitude and magnitude, we estimated the magnitude of detected events. We then compared the minimum magnitude of completeness (MC) before and after detection within one day of mainshock, and found that the minimum magnitude of completeness was reduced from ML1.2 to ML0.7, showing that the minimum magnitude of completeness in the Qilian area of the Qinghai Seismic Network was about ML0.7. In addition, the b value of seismicity decreased slightly after the detection, and the results showed that the b value decreased markedly within a short time after the mainshock. Using the template matching method can effectively reduce the number of loss events caused by the earthquake coda wave interference, and improve the capability of seismic detection. The b value of further accurate calculations of earthquake aftershocks can help us better track earthquake activity.