The TMD reported yesterday's short, sharp and noisy quake as being centred under Srisoonthorn in Thalang District, with a strength of 4.3 on the Richter scale.
The USGS has placed the epicentre to the east of that, 10 kilometres beneath the strait between Koh Yao Yai and Noi, with a strength of 3.9 Richter.
Local reports all agreed that the quake felt and sounded like a truck (or in one reader's description, a Jumbo jet) hitting the building they were in.
In Patong, the jolt sparked an immediate exodus, with locals and tourists heading straight for the hills without waiting to hear whether there was any tsunami risk.
Generally speaking, tsunamis are rarely caused by earthquakes of less than 7.5 magnitude on the Richter scale - massively stronger than yesterday's temblor.