The United States Geological Survey (usgs.gov) reported an initial quake strength of 8.7 on the Richter scale.
There were two major aftershocks, one of 6.5 Richter and one of 8.2.
AFP quoted Victor Sardina, a geophysicist with the US Pacific Tsunami Warning Center in Hawaii, as saying the tsunami generated was "not anywhere near" as large as the devastating tsunamis that struck Asia in 2004 or the one that hit Japan last year.
The 2004 Asian Tsunami, was recorded at 9.1 Richter - roughly 5.6 times stronger than yesterday's temblor - which was, however, still perfectly capable of triggering a tsunami.
Mr Sardina said the tsunami measured a mere 35 centimeters (14 inches) near Padang, Indonesia, but could swell to as high as a meter (three feet) near Sri Lanka, adding that US scientists were still carefully monitoring the situation.
On the Andaman coast, scientists reported that they had detected a 10-cm high wave.
The non-appearance of the tsunami this time was apparently down to the quake being different from the one in 2004.
AFP also quoted an expert with the British Geological Survey, seismologist Susanne Sargeant, who explained that the earthquake's movement was horizontal, not vertical. It occurred 33 kilometres below the sea bed and caused no apparent movement of the sea floor, which is what triggers tsunamis.
"We've had two blocks rubbing together, it's called a strike-slip earthquake."
"That means there hasn't been any displacement of the sea floor. Although an earthquake of this magnitude has the potential to cause a large tsunami, the fact that we haven't seen any drop of the sea floor, which is what generates the wave, it looks like the possibility of a tsunami being generated is low."
In Phuket, the evacuation appeared to go well, with hundreds of thousands taking to the hills or climbing atop tall buildings.
The airport was closed as a precautionary measure, but reopened after the all-clear.
Airport director Prathuang Sornkham said, "News of the earthquake yesterday may have some impact in tourism during the Songkran festival but now Phuket International Airport is available so the impact should not be great.
"However, we should wait and check today to make tourists more confidence in travelling in Phuket."