Characteristic and Analysis of Seismic Waveforms near Field Underground Chemical Explosions in Loess

摘要

It is obvious that waveforms underground explosions of hundred level in loess have shorter duration.With the increase of the distance,wave durations vary longer,dominant frequency of the waveform gradually decreases,and dominant frequency band of Fourier spectra expands to lower frequency.Seismic frequency band is between 1.5 Hz and 20.Comer frequency is about 20Hz.Seismic waveforms mainly show two kinds of wave trains,namely,longitudinal and transversal waves.It is very obvious that difference of amplitude exists between near the explosion and away from the one.Near the explosion,transversal wave is larger than longitudinal wave.Far from the explosion,longitudinal wave is stronger than transversal wave.Amplitude ratio of the transversal waves to longitudinal waves decreases with the increase of the distance,the ratio decreases quickly near the explosion,and it decreases slowly far from the explosion.Longitudinal wave velocity is approximately 2.3Km/s,transversal wave velocity is approximately 1.1Km/s.Wave velocity decreases with the increase of the distance,and attenuating index is about-2.6.