Truly awful scenes coming out of Beirut.
It seems the explosion(s) was so strong, it was picked up on seismometers up to 500 km away. This seismic section shows signals consistent with a location of Beirut. Not sure if we are seeing 2 sources or a secondary seismic arrival.

The signal from the secondary later arrival at ~2000 seconds has a very different waveform shape and duration compared to the first signal, so I'm not entirely sure if these records are showing 2 different explosion sources.
(Thanks to @mrbrianolson for the heads up)

@LastQuake have located the first of these signals with a seismic event that has its epicentre at Beirut and with a magnitude of 3.5.
https://www.emsc-csem.org/Earthquake/earthquake.php?id=882410#summary

Here's a slighter clearer version of that record section without the transparent background