Purpose: The study lies in investigating the waveforms and the spectral content of the infrasonic signals generated by multiple explosions at an ammunition depot versus energy and distance. The aim of this study is investigating the features of the waveforms, amplitudes, and spectral content of the infrasonic signals which propagated over long distances (~ 150 to 180 km) from the ammunition depot near Vinnytsia (Ukraine) on September 26–27, 2017 during the man-caused catastrophe.Design/methodology/approach: The Ukrainian network of infrasonic stations was used to study the basic parameters (spectral content, amplitudes, predominant oscillation periods, duration of the oscillation trains, celerity) of the infrasonic waves which propagated over long distances (~ 150 to 180 km). The signal processing technique in this study added up to the following. First, the time dependences of atmospheric pressure fluctuation acquired in relative units were converted into absolute units. Then, they were filtered within the period range of 0.2 to 10 s. Next, the filtered variations were subjected to the system spectral analysis that includes the short-time Fourier transform, the Fourier transform in a sliding window with a width adjusted to be equal to a fixed number of harmonic periods, and the wavelet transform. In the latter transform, the Morlet wavelet was used as the basis function.Findings: It was shown that an upward trend in the amplitude and period of the predominant oscillation were observed when the energy release increased from 3 to 53 tons of TNT, while the duration of the oscillation trains increased from ≈1.5 to 2 min. The infrasonic signal parameters were determined to change insignificantly when the distance between the explosion epicenter and an infrasonic station location changed a little (by 15 to 18 %). The differences in the wave forms are related to orientation of the propagation path. The analysis has revealed that the harmonics in the 3 to 5-6 s period range were predominant when the energy release was equal to 53 tons of TNT. The duration of the trains of oscillations with such periods amounted to 40 s. The average celerity was calculated to change within 300 to 309 m/s for different propagation paths with stratospheric wave reflections, that provides evidence for the influence of the wind in the upper atmosphere on the infrasound propagation. The thermospheric reflection resulted in the signal amplitude smaller by a factor of a few times and the celerity equal from 245 to 250 m/s.Conclusions: The basic parameters of infrasonic signals generated during the recurrent explosions at the ammunition depot near Vinnytsia and propagating in the atmosphere have been studied.
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机译：目的：该研究在于调查在弹药仓库与能量和距离处产生多个爆炸产生的射频信号的波形和光谱含量。本研究的目的正在研究2017年9月26日至27日在Vinnytsia（乌克兰）附近的弹药仓库（乌克兰）的长距离（〜150至180公里）的速率波形，幅度和光谱含量的特征在人造的灾难期间。设计/方法/方法：乌克兰的速率网络用于研究在长距离传播的速率波浪的基本参数（光谱含量，振幅，主要振荡周期，振荡训练持续时间，圆锥形）（〜150 180公里）。该研究中的信号处理技术增加了以下内容。首先，将在相对单元中获得的大气压波动的时间依赖性转化为绝对单位。然后，它们在0.2至10秒的期间范围内过滤。接下来，对滤波后的变化进行系统谱分析，该系统谱分析包括短时傅里叶变换，在滑动窗口中的傅里叶变换，宽度调整为等于固定数量的谐波周期，以及小波变换。在后一种变换中，Morlet小波用作基本功能。结果表明：当能量释放从3〜53吨TNT增加到3至53吨TNT时，观察到幅度和周期的上升趋势，而振荡列车的持续时间从≈1.5增加到2分钟。当爆炸震中器和Infasonic站点之间的距离变化时，确定速率信号参数变化很大地改变（乘以15至18％）。波形的差异与传播路径的取向有关。分析显示，当能量释放等于53吨TNT时，3至5-6秒周期范围内的谐波是主要的。振荡列车的持续时间为40秒。计算平均圆锥度以改变300至309 m / s的不同传播路径，其具有平坦散波反射，为风在上层大气中的影响提供了基础传播的证据。热散反射导致信号幅度小的倍数几次，圆锥度等于245至250米/秒。结论：研究了在Vinnytsia附近的弹药仓库和在大气中传播的弹药码头爆炸中产生的速率产生的基本参数。
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