Seismic and infrasonic analysis of the 9 March 2014 fireball in South Korea

Abstract

On the evening of 9 March 2014, a bright fireball was observed in many places in South Korea, the energy associated with the event was also recorded at local seismic and regional infrasound stations. Using impulsive seismic signals recorded at 19 stations, we calculated the possible extent of the sonic source of the fireball by assuming point- and line-source models, which might be physically linked to either a point-source explosion in the atmosphere or shock waves radiating from the fireball’s trail, respectively. By comparing the observed seismic arrival times with those predicted by both models, a line-source model resulted in better solution than a point-source model. It means that shock waves along the meteor’s high-speed passage through the atmosphere probably acted as the dominant source of the seismic signals. The parameters of the fireball’s sonic trajectory, after incorporating a realistic sound velocity model of the atmosphere, are estimated to be an azimuth arrival angle of 313.5° clockwise from the north and an elevation arrival angle of 44.5° above the Earth’s surface, with a time of 11:04:51 UTC at which the trajectory meets the Earth’s surface. The estimated ground impact point is about 2 km offset from locations where meteorites associated with the fireball were found. The line-source model also explained the large azimuthal deviation of infrasound waves observed at arrays in the vicinity of the trajectory. From the infrasound measurements, the kinetic local-source energy generating the sound was estimated to be approximately 0.8 tons TNT, based on semi-empirical relations for the point- and line-source models.