Helicopter Crash on the Spitsbergen Archipelago: Infrasound and Seismic Signals Decryption

Abstract

A Convers Avia Airline Mi-8 helicopter crashed near the Russian settlement of Barentsburg on October 26, 2017. The moment of impact was recorded by the Barentsburg seismo-infrasound array 2.5 km from the crash site. The seismo-infrasound array consists of a micro-aperture infrasound group, including three low-frequency microphones and a broadband seismic station located at the same site. A detailed analysis of the obtained records of the seismometer and the low-frequency microphones is presented here. Two types of signals determined by the helicopter fall are detected in seismic channels: a wave caused by the water impact of the helicopter and propagating through the earth, and an air wave that was also generated by the water impact but propagating through the atmosphere. The second type of wave was also recorded by low-frequency microphones from the infrasonic microgroup. The procedure for determining the source coordinate by the complex analysis of acoustic and seismic signals is described. The difference in arrival times of seismic and acoustic waves is used to determine the distance to the source, and the back azimuth is calculated using the differences in the arrival times of the acoustic wave to the spaced microphones of the infrasound microarray. The records of the acoustic signals associated with the operation of the helicopter rotor before the crash and at the moment of water impact are examined. A detailed analysis of the frequency and amplitude composition of the received seismic and infrasound signals has allowed us to not only determine the exact place and time of the helicopter crash, but also to estimate the expected trajectory of its movement before the fall, as well as to recreate some details of the accident.