A strong earthquake and a series of aftershocks struck off the southern Philippines today, officials said, but they occurred at such great depths that their impact dissipated and there were no reports of casualties or damage.
No tsunami warning was issued.
In just over an hour early today, an earthquake and two aftershocks recorded at magnitudes of 7.3 to 7.6 by the US Geological Survey, at considerable depths of between 576km and 617km southwest of Cotabato on Mindanao island.
An aftershock of 6.2 magnitude was measured in the same area at 1:35 pm (5.30am Irish time) today, the USGS said, at a depth of 564 km. The magnitude was initially reported at 6.7.
"We expect these aftershocks, but we don't expect them to cause any damage," Renato Solidum, head of the Philippine Institute of Volcanology and Seismology, told reporters, adding there had been 68 aftershocks.
"These are too deep and the energy that it had generated weakened as it travelled up to the surface."
After the first set of quakes, Solidum had said they were felt only at intensity 2 in most parts of the southern island of Mindanao. The earthquake struck at 6.08 am (10.08pm Irish time) about 103 km southwest of Cotabato.
"The earthquake was not caused by movement in an active faultline, but by the sinking of the Moluccas plate," he said.
"It has been sinking for some time, causing major tremors, but these were too deep to cause any damage. There's nothing to worry about."
A quake of over 7.0 magnitude can cause widespread damage.
People in Cotabato, where the tremor was felt at intensity 2, were unaware of the early morning quake.
"There was no shaking, I never felt anything," said hotel worker Jap Rabino. "It's business as usual."