<p>The underwater quakes struck at a depth of between 575 and 605 kilometres, just over 100 kilometres southwest of Cotabato, on the island of Mindanao, said the US Geological Survey.<br /><br />The Hawaii-based Pacific Tsunami Warning Centre said no destructive tsunami was generated by the 7.3-, 7.6- and 7.4-magnitude quakes, the first of which hit at 6:08 am (0338 IST).<br />"It was kind of mild," said Monisa Tulawie, a staff member at the Cotabato city mayor's office, who told AFP she felt one of the quakes.<br /><br />Other residents contacted by phone were unaware of what had happened, saying they had not been woken by the tremors.<br /><br />"We have received no reports of damage or casualties," said local fire official Marlon Macapili of the Autonomous Region in Muslim Mindanao, a self-ruled area that includes four provinces around Cotabato.<br /><br />Renato Solidum, chief of the Philippine Institute of Volcanology and Seismology, said the strong quakes struck over a 67-minute period at sunrise, with several moderate aftershocks.<br /><br />Mild tremors were felt as far as north Manila, more than 800 kilometres away, he added.<br /><br />"We don't expect any," Solidum told AFP when asked about damage or casualties. "Because of their depth they will not be able to depress the ocean floor," Solidum added.<br /><br />The institute said quakes with a magnitude of 7.0 or above can cause considerable damage near their epicentre, while shallow-seated ones occurring under the sea may generate huge waves.<br /><br />The Philippines is an archipelago of more than 7,000 islands with many people living in communities close to the sea.<br /><br />The country sits on the Pacific Ring of Fire, where continental plates meet, causing frequent seismic and volcanic activity.<br /><br />Solidum said a movement of the Molucca Sea Plate had caused today's quakes. The plate is pushing underneath the Indonesian archipelago.<br /></p>
<p>The underwater quakes struck at a depth of between 575 and 605 kilometres, just over 100 kilometres southwest of Cotabato, on the island of Mindanao, said the US Geological Survey.<br /><br />The Hawaii-based Pacific Tsunami Warning Centre said no destructive tsunami was generated by the 7.3-, 7.6- and 7.4-magnitude quakes, the first of which hit at 6:08 am (0338 IST).<br />"It was kind of mild," said Monisa Tulawie, a staff member at the Cotabato city mayor's office, who told AFP she felt one of the quakes.<br /><br />Other residents contacted by phone were unaware of what had happened, saying they had not been woken by the tremors.<br /><br />"We have received no reports of damage or casualties," said local fire official Marlon Macapili of the Autonomous Region in Muslim Mindanao, a self-ruled area that includes four provinces around Cotabato.<br /><br />Renato Solidum, chief of the Philippine Institute of Volcanology and Seismology, said the strong quakes struck over a 67-minute period at sunrise, with several moderate aftershocks.<br /><br />Mild tremors were felt as far as north Manila, more than 800 kilometres away, he added.<br /><br />"We don't expect any," Solidum told AFP when asked about damage or casualties. "Because of their depth they will not be able to depress the ocean floor," Solidum added.<br /><br />The institute said quakes with a magnitude of 7.0 or above can cause considerable damage near their epicentre, while shallow-seated ones occurring under the sea may generate huge waves.<br /><br />The Philippines is an archipelago of more than 7,000 islands with many people living in communities close to the sea.<br /><br />The country sits on the Pacific Ring of Fire, where continental plates meet, causing frequent seismic and volcanic activity.<br /><br />Solidum said a movement of the Molucca Sea Plate had caused today's quakes. The plate is pushing underneath the Indonesian archipelago.<br /></p>