Philippine Institute of Volcanology and Seismology (Phivolcs) warns of further aftershocks from the 6.7 magnitude earthquake that hit Surigao City and Surigao del Norte Friday night.
Phivolcs science research analyst Paulo Sawi cautioned against occupying structures already damaged by the earthquake, warning aftershocks can further harm these.
"People must avoid staying inside and even going near such structures," he said.
He urged such precaution, expecting in forthcoming days further aftershocks from the earthquake.
Such aftershocks would likely be of lesser magnitude than the 89 others Phivolcs reported as of 5 a.m. Saturday but some of these could still be damaging if occurring at shallow depths, he noted.
"Owners must have their earthquake-damaged structures checked first so repair work can be done if this is still possible," he said.
Phivolcs Director Renato Solidum sees need for the public to learn anticipating natural hazards' consequences and to act on these accordingly.
"It's important to be always ready to react correctly," Solidum said after a magnitude 6.7 undersea earthquake of tectonic origin jolted Surigao del Norte province's vicinity late Friday night.
He noted being knowledgeable and pro-active about earthquakes and other natural hazards can help spell the difference between life and death.
Latest Phivolcs data show the 10:03 p.m. offshore earthquake this Friday struck 14 kms north 78° west of Surigao del Norte's Surigao City at a depth of 11 kms only.
Less than an hour after the earthquake struck, Phivolcs said available data indicate this event would unlikely generate a tsunami.
National Disaster Risk Reduction and Management Council (NDRRMC) said in its situation report 1 released Saturday that the earthquake damaged a bridge as well as several establishments and houses in Surigao del Norte.
NDRRMC also said families in Surigao del Norte's capital Surigao City evacuated to higher ground there, fearing possible onslaught of tsunamis.
Solidum sees nothing wrong with such evacuation even if Phivolcs assured the earthquake won't generate tsunamis, however.
He noted the evacuation was still better than having noprecautionary action as occurrence of a "strong" earthquake like Friday's tremblor is among indications a tsunami might ensue.
According to Phivolcs, tsunami is "a series of sea waves commonly generated by under-the-sea earthquakes."
"Tsunami can occur when the earthquake is shallow-seated and strong enough to displace parts of the seabed and disturb the mass of water over it," Phivolcs said.
Phivolcs traced the earthquake to movement of the Philippine Fault Zone (PFZ).
PFZ is a 1,200 km-long major tectonic feature transecting the Philippines from northwestern Luzon to southeastern Mindanao.
Two PFZ segments' strike-slip or horizontal movement against each other triggered Friday's earthquake, noted Phivolcs science research specialist Mylene Enriquez.
She noted such movement didn't displace water so there was no tsunami after the earthquake, however.
"The earthquake's magnitude was insufficient to generate a tsunami," she also said.
Earlier, Phivolcs said Friday's earthquake was felt at intensity VI in Surigao City and Pintuyan, Southern Leyte; intensity V in Mandaue City, San Ricardo, Limasawa and San Francisco, Southern Leyte; intensity IV in Hinunangan, Southern Leyte and Butuan City; intensity III in Hibok-Hibok, Camiguin, Tolosa and Tacloban, Leyte, Bislig City,Gingoog City, Misamis Oriental as well as intensity II in Cagayan de Oro City, Talocogon City, Agusan del Sur, Dumaguete City and Cebu City.
"The earthquake struck at a shallow depth only so this tremblor was felt even in communities already far from its epicenter," said Sawi.
Phivolcs also reported instrumental readings of intensity II in Bislig City and intensity I in Cebu City and Cagayan de Oro City.