| Identification to the first break wave and its arrival time for shallow ground vibrationsignals are important parameters of earthquake source detection and positioning. Vibrationsignal SNR, especially the diversity of wave patterns when detecting closely to theearthquake source, has seriously affected the precision of picking up the first break forvibration signals, and thus produced a great impact on the accurate positioning of the source.Precise picking method of vibration signal first arrivals and its positioning technologyunder field geological conditions are researched in the paper, and it has very importantapplication value and theoretical significance in engineering fried positioning, earthquakelocation, blasting, coal mining and pipeline safety monitoring, oil exploration andgeological exploration, etc.Based on the analysis of the seismic signal theory and the developing situation of thefirst break picking method, the paper builds a the distributed vibration signal acquisitionsystem using acceleration sensor, which has passed the test and acquired the seismic signalof the shallow ground vibration test, meanwhile the time-frequency characteristics of thevibration signal is analyzed and the seismic signal is denoised using wavelet thresholddesnoising methods. Aimming at the pattern diversity of the fluctuation mode and theproblem of big random noise outside, a first break picking technique based on the energyfactor method and3-component phase identification method is discussed; the accuracy anderror of the two locating methods are also analyzed and compared.The simulation analysis and experimental results indicate that the accuracy of the firstbreak picking can be effectively improved via vibration signal preprocessing and the theenergy factor method is better than the3-component phase identification method. Whenlocating the hypocenter with the positioning algorithm, the root mean square error of theexplosion position calculated can reach to0.6029m. |
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