What happened last night? Was it an earth tremor?

At around 22.45hrs last night lots of people heard/felt something on Islay - but there are no reports of an earth tremor on the net, not that we have been able to find anyway.  Some people describe 'feeling' something, others heard a loud noise/rumble.

Does anyone know what it was?  Suggestions include an earth tremor, explosion, thunder, a strong gust of wind - or an aircraft breaking the sound barrier.  We once heard the Space Shuttle coming in  to land at Edwards Air Force Base in California and when it passed overhead in the San Fernando Valley it made a similar (actually louder) noise...

Carl

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