Analysis of infrasound signals generated by quarry blasts

The ISCO infrasound array has been installed at the Conrad Observatory (Austria, ~ 50 km SSW Vienna) since January 2021. Among the signals detected, regularly recurring signals can be attributed to blasting in a limestone quarry located ~ 16 km away. The characteristic signal shape and the availability of blasting data provided a basis for an in-depth analysis of these signals.We consider the interaction of the rock mass set in motion by an explosion with the atmosphere to be the source of the signals. We derive the kinematics of the blasted rock masses, in particular the change in volume, from photogrammetric documentation of the deposits and numerical modeling of the ejection process. We limit ourselves to 1D modeling of the blasts as an infrasound source, since the dominant wavelength of the signal, at ~ 500 m, is a factor of 10 greater than the dimensions of the blasted rock masses. A source function based on the ‘vibrating sphere’ model in conjunction with a transfer function corresponding to reverberation allows excellent modeling of the signal shape. As the cause of the reverberation, we present an analogy between the shape and acoustics of classical amphitheaters and the shape of the open-cast mine and its possible acoustic effectiveness.The amplitude of the source function based on the ‘vibrating sphere’ model correlates very well with the total amount of explosives used in a blast (R2 = 0.87). There is considerable variation between these two parameters and the peak-to-peak amplitude of the infrasound signal (R2 = 0.37).