Abstract: Precise and Active Seismic Monitoring (PASM) system introduced in this paper may provide an approach to explore crustal structures and monitor its temporal variation. With the increase of propagation distance, useful signal is masked in strong noise as the energy intensity radiated by it is quite small. Strong noise has a great impact on identifying phases and picking accuracy of travel time. In this study,we propse a new method for time-varying narrow band-pass filter design to achieve precise filtering effect, and retrieve CASS chrip signal by cross-correlation to identify the major seismic phases traveling through the crust. Besides, because of different travel time between different seismic phases, we retrieve certain impulsive seismic waveforms by using time-varying narrow band-pass filter, which suppresses the other seismic phases. Finally,The effectiveness and practicability of the new optimized algorithm in extracting chrip signal, raising the resolution phase and seismic phases separation is proved by applying it to model and actual seismic data. The retrieved impulsive seismic waveforms at station 200 km away reflectes the capacity of weaker signal detection.

Key words: Signal detection, CASS, Resonators, Time-varying filter