We need more data. I like it as a hypothesis, but we really need to date the seismites properly. S&G and the Decapolis could have been Bronze Age settlements, only 4,000 years ago or less. There must be evidence. Tall el-Hammam is a good candidate, two centuries later than Ussher’s date. Raining ignited bitumen is a good hypothesis. Easy to prove.
[If 10 cities - fortified settlements - in an area of at least 500 km^2 (50 x 10 km), were annihilated by a rain of burning bitumen, ejected and ignited from a fault by a Mw (Moment Magnitude) 7.8–8.5 (around 7 on the old Richter) earthquake, the equivalent of an at least 100kton nuclear explosion, only 4 thousand years ago, I’d expect a layer. Order of magnitude we’re talking 1-10 million cubic metres of bitumen. Call it 1, moving at 100 m/s. From a reservoir 1 km sq 1 m deep. It wouldn’t not leave evidence. A comet airburst is vastly less possible, at least 100 times.]