The two were just two minutes apart.

According to the TMD announcement, the first quake was at 4.44pm with a rating of 4.3 on the Richter scale. The center was 10 km below the surface, in Tambon Srisoonthorn, in Thalang District.

The second, at 4.46pm, rated at 5.5 Richter (5.3 according to the US Geological Survey, or USGS) was centred close to Sumatra, at a depth of 10 kilometres.

A spokesperson for the TMD, Phuwiang Prakammin, told the Thai PBS TV channel that the first quake in Thalang was probably the reason people on the island felt that the quake was much stronger than was reported by the USGS.

“We believe the April 11 quake had an impact on the fault lines in or close to Thailand,” said Mr Phuwiang.

“We can’t say what level any future quake will be, but we can say there has been some disturbance in the equilibrium [of local fault lines],” he added.

The fault system affected is known as the Klong Marui fault, which lies under Surat Thani, Phang Nga, Krabi and Phuket.

The USGS has not reported the quake, though it has recorded a further 4.2 Richter temblor of Sumatra, at 6:57 this evening.