A massive explosion in the city of Beirut, Lebanon, sent shock waves across the ground, triggering an earthquake felt more than 250 kilometers away from the explosion center. Eyewitness accounts describes widespread shacking of buildings and the ground. The seismic waves were recorded by the seismographic network of the Geological Survey of Israel and seismic stations along the Syrian border to Turkey.
According to first estimates by geologists, the blast was equivalent to a magnitude 4.5 earthquake, comparable to the energy released by the detonation of 1.000 tons of TNT. The U.S.G.S. gives a magnitude of 3.3. The reported magnitude is not directly comparable to an earthquake of similar size because the explosion occurred at the surface where seismic waves are not as efficiently generated. News reports state the explosion was caused by the deflagration of 2.750 tons of ammonium nitrate stocked in the port district of Beirut, which is roughly equivalent to 1.100 tons of TNT.
A diagram shared by Jugurtha Kariche, a geologist at the Institute de Physique du Globe in Strasbourg, France, shows the typical seismogram caused by an explosion.