Seismic Location of the 4 August 2020 Beirut Port Chemical Explosion

On 4 August 2020 Lebanon's capital, Beirut, was rocked by a sequence of colocated fires and chemical explosions that left hundreds of people dead, thousands injured and homeless, demolished the city's seaport, and heavily damaged the surrounding neighborhoods and businesses. The event was well recorded by many regional seismic stations in and around the eastern Mediterranean Sea. Using a network of 58 stations, 105 regional seismic phases, and a Bayesian methodology places the event at 1.8 km south of the ground-truth location, the seaport warehouse. Achieving this accuracy is significant, considering very limited local seismic data were available to use in this study. The location bias is attributed, in large part, to a small but statistically significant difference in the Moho velocity for sea paths compared with continental paths. The depth to the Moho is generally consistent with the iasp91 model. Concurrent to the port explosion is a series of unrelated small explosions, 11 s apart, attributed to a seismic survey that was being carried out at the time in the eastern Mediterranean Sea using air guns.