A MAJOR incident during the Syrian civil war is helping to pin down the seismic signature of distant bombs.

Although seismologists have long monitored nuclear explosions, any nuclear tests since 1980 have taken place underground. Measurements of smaller, conventional explosions on or near the surface are relatively rare.

Accurate models of such blasts could help interpret seismic readings and allow rescuers to deal with incidents in war zones or industrial accidents. “Knowing the yield and depth of large, shallow explosions is useful to government agencies from an emergency response perspective,” says Michael Pasyanos of the Lawrence Livermore National Laboratory in California.

Working with colleague Sean Ford, Pasyanos added a dampening effect to existing models to account for how shallow seismic waves are weakened when they pass from the ground into the air. To do this, they used data from controlled explosions at the US army White Sands Missile Range, New Mexico, in 2012 (Geophysical Research Letters, doi.org/38p).


They were also able to test and refine the new model using seismic readings from May last year, picked up when rebels blew up an army base in north-west Syria.

They tested the model on a large explosion last May, when rebels blew up a Syrian army base

The model gave the cause of the explosion as a bomb equivalent to between 6 and 50 tonnes of TNT, depending on the assumed depth. The rebels claimed to have used a 60-tonne bomb, so it is possible they were exaggerating or that the explosives were of poor quality and did not fully detonate.

How accurate the model will prove depends on knowledge of the local geology, says Sam Toon of Keele University, UK, but he thinks it will be useful. “With things like the rebels in Syria, it gives you an idea of the capabilities they’ve got, what kind of explosives they might have access to.”

This article appeared in print under the headline “Syria war hones our seismic image of bombs”