Fig. 1. Schematic of the model of the DAS system monitoring the vibration source and signal waveform of the vibration source. (a) Monitoring model; (b) signal waveform of the vibration source

Fig. 2. Signal of the vibration source acquired by the DAS system. (a) Two-dimensional diagram of the vibration signals; (b) single-channel signal diagram with different signal-to-noise ratios

Fig. 3. Schematic diagram of edge detection extraction of arrival time. (a) Grayscale map after bilateral filtering; (b) extracted edge features map; (c) arrival time curve binary map

Fig. 4. Schematic diagram of DAS system monitoring source

Fig. 5. Site layout diagram of field experiments

Fig. 6. Comparison of bilateral filtering noise reduction results. (a) Grayscale map of raw data; (b) grayscale map after bilateral filtering; (c) comparison of the 30^th channel data noise reduction

Fig. 7. Arrival time pickup result of vibration source initial arrival wave. (a) Arrival time pickup results; (b) arrival time detail

Fig. 8. RMSE of arrival time pickup result

Fig. 9. Comparison of the effects of different arrival time pickup methods