Two earthquakes struck six minutes apart on Monday when the country was on holiday as part of its annual observance of Mother's Day.

Neither of the two quakes was strong enough to generate a tsunami, according to two separate earthquake bulletins issued by the Apia-based Samoa Meteorological Service on Monday.

The first tremor recorded a 5.2 magnitude on the Richter scale and occurred at 3:26pm Samoan local time in the Tongan islands region. The distance from Apia was 491.13 kilometres, south southwest with a depth of 10 kilometres.

The second quake occurred at 3:33pm Samoan local time in the Samoa region 226 kilometres south southwest of Apia. It registered a 4.2 magnitude also with a depth of 10 kilometres.

“No tsunami threat for Samoa,” said the Meteorological Service in both bulletins.

For the purposes of monitoring earthquakes and tsunamis and issuing alerts for the region, Samoa-Tonga is called ‘Region One’ according to information on the Meteorological Service website.

Quakes that occur in Region One and register at least a 6.4 on the Richter scale result in the issuing of a national tsunami advisory.

Stronger tremors measuring between 6.5 and 7.4 on the Richter scale warrant a national tsunami watch. In other words, people should prepare for evacuation.

While earthquakes 7.5 on the Richter scale call for a national tsunami warning or code red which means evacuate immediately.

The Meteorological Service is responsible for seismic monitoring in Samoa and operates a network of seismographs that provide real time and continuous monitoring of earthquakes and study of ground motion.

The seismic information collected is streamed into Samoa's National Tsunami Warning System. The Meteorological Service provides tsunami warnings and alerts for Samoa.