CHARACTERISTICS AND IDENTIFICATION OF NON-NATURAL EARTHQUAKES IN URUMQI AND SURROUNDING AREAS OF XINJIANG
Twenty blasting events,five collapse events and 25 seismic events recorded by ML2.4～3.8 Xinjiang Seismic Network from 2017 to 2023 were selected.The waveform recording characteris-tics,vertical P-wave initial direction,amplitude ratio and time-frequency analysis method were used to study the characteristics of non-natural earthquakes.The analysis results show that there are obvi-ous differences between non-natural earthquakes and natural earthquakes in time domain and fre-quency domain.The vertical P-wave of blasting events develops upward,the period is small,the amplitude and period of S-wave do not change significantly,and it is easy to be confused with sur-face waves.The collapse event is vertically downward P wave,P wave S wave appears in groups and is close to each other,and the waveform is simpler than blasting.The vibration attenuation of both is fast,and the surface wave is developed.The value of blasting Pc/Sm is greater than 0.42,the earthquake is less than 0.42,and the value of collapse Pc/Sm is greater than 0.62.The value of Pm/Sm of blasting is greater than 0.70,the earthquake is less than 0.70,concentrated at about 0.40,and the value of Pm/Sm of collapse is about 0.55.In terms of time-frequency analysis,the frequency components of earthquakes and collapses are simple,the energy peak is below 4 Hz,the frequency domain is narrow,mainly low-frequency surface waves,and the attenuation is fast,show-ing the characteristics of"few peaks".The seismic frequency components are complex,distributed between 4 Hz and 16 Hz,the frequency domain is wide,the main frequency is not fixed,showing"multi-peak"characteristics,and the energy is distributed in the S wave.The above identification criteria provide an effective reference for distinguishing the characteristics of non-natural earthquakes in the study area in the future.
Non-natural earthquakesExplosionCollapsesWaveform characteristicsAmplitude ratio
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