SYDNEY—A 7.4-magnitude earthquake struck 255 kilometres (158 miles) southwest of Tonga early Friday, according to the US Geological Survey.
The under-sea quake struck at 5:19 a.m. (1719 GMT Thursday) and sparked a tsunami alert, although no damage was expected due to its depth of 171 kilometers, according to the Pacific Tsunami Warning Center.
The earthquake, centred 282 kilometers southwest of Tonga’s capital Nuku’alofa, was followed four hours later by a second powerful 6.6 tremor 84 kilometers northwest of the town.
The second quake, at a depth of 103 kilometers, also generated a tsunami warning.
“A destructive tsunami was not generated based on earthquake and historical tsunami data,” the center said of each quake.
The two quakes come 12 days after a similar 6.5-magnitude earthquake struck the area, at a depth of 205 kilometers.
Tonga, almost 2,000 kilometers (1,240 miles) northeast of New Zealand, lies on the so-called Pacific “Ring of Fire,” where continental plates collide causing frequent seismic activity.