COTABATO CITY, Philippines – At least 196 aftershocks were felt yesterday in many parts of the Visayas and Mindanao after Friday’s magnitude 7.6 earthquake which forced hundreds in coastal communities to flee to higher ground due to threats of tsunami.
The Philippine Institute of Volcanology and Seismology (Phivolcs) lifted yesterday its tsunami alert and advised local officials to implement an orderly return of evacuees to their communities.
The latest report of aftershocks came at 6 p.m. yesterday.
Phivolcs director Renato Solidum said there were no signs of any approaching destructive tsunami shortly after midnight Saturday.
“Phivolcs is canceling all tsunami alerts associated with the magnitude 7.7 earthquake (later changed to magnitude 7.6) that occurred at 8:47 p.m. (Philippine Standard Time) on Aug. 31, 2012. The local government of affected coastal provinces may now advise and assist those who evacuated to safely return to their communities,” the agency said in its Tsunami Bulletin No. 2 issued at 12:10 a.m. yesterday.
“Initial reports of sea level disturbance received by Phivolcs indicate that the tsunami generated by this earthquake did not reach life-threatening heights,” it added.
Solidum said aftershocks normally happen after a major tremor. He recalled that last February, close to a thousand aftershocks were recorded by Phivolcs following an earthquake in Negros Oriental.
Minutes after the earthquake Friday night, Phivolcs raised tsunami alert level 3 over Samar, Southern Leyte, the Surigao provinces, and the Davao region.
Two hours later, the Pacific Tsunami Warning Center lowered the alert level in Indonesia but the alert level in the Philippines remained due to monitored small tsunami waves.
Surigao City was hit by a small tsunami of up to 19 centimeters at 10:48 p.m. Friday.
The Pacific Tsunami Warning Center also reported a 3 cm tsunami in Legazpi City at 9:43 p.m. and in Davao City at 9:50 p.m.
Waves of close to half a meter high were also reported in Pilar, Surigao del Norte about 10 minutes after the earthquake.
In its bulletin, Phivolcs said the earthquake’s epicenter was traced at 10.83°N, 126.71°E – 112 km S 78° E of Guiuan in Eastern Samar.
Intensity 7 earthquake was also reported in Oras, Sulat, and Borongan City in Eastern Samar; Intensity 6 in Siargao, Surigao del Norte, Tacloban City, Palo, Leyte, St. Bernard, Southern Leyte; Intensity 5 in Mati City, Compostela, Legaspi City, Iloilo City, Bislig City, Iligan City; Intensity 4 in Butuan City, Catbalogan City, Cagayan de Oro City, and Davao; Intensity 3 in Cotabato City, Mambalao, Camiguin, General Santos City; and Intensity 2 in Marawi City and Sipalay City.
Warning
Disaster officials, meanwhile, said last Friday’s earthquake should serve as a wake-up call to authorities and to people living in the vicinity of the West Valley Fault which stretches between Angat in Bulacan and Taal Lake in Batangas.
“The movement of the Philippine trench is long overdue, just like the other fault lines within the so-called Pacific Rim of fire,” said Edgardo Ollet, operations chief of the National Disaster Risk Reduction and Management Council-Office of Civil Defense (NDRRMC-OCD).
Ollet said the movement in the Philippine trench, which triggered last Friday’s earthquake, might cause some movements in the West Valley Fault.
The Philippine trench is located in the country’s eastern seaboard and stretches toward Japan up to the San Andreas Fault in the United States.
The West Valley Fault passes through several highly urbanized areas with high-rise buildings in Metro Manila.
Ollet said that while there is no way to predict an earthquake, it’s best for everyone to prepare for the worst.
He said administrators of high-rise structures, especially those located in southern Metro Manila, should conduct regular earthquake drills for all building occupants.
“If the Philippine trench moved Friday, there is always that assumption that other fault lines have been affected and will also move. When? That we don’t know. All we can do is to be prepared,” Ollet said.
He cited several destructive earthquakes including the one on Feb. 17, 2006 that triggered a mudslide that wiped out the entire Barangay Guinsaugon in St. Bernard, Leyte.
A 7.9 intensity earthquake on July 16, 1990 killed thousands in Luzon.
Residents of high-rise buildings should at least keep flashlights, medicine, canned goods, bottled water and whistles within reach in case of emergency, he said.
Metro at risk
Sen. Loren Legarda, for her part, said Friday’s powerful earthquake should serve as reminder that much has yet to be done to ensure the disaster preparedness of Metro Manila.
Legarda called the attention of concerned government agencies to the 2004 Metro Manila Earthquake Impact Reduction Study (MMEIRS), which indicated that a 7.2 magnitude quake in the nation’s capital could cause massive destruction and countless deaths.
“The MMEIRS revealed high casualties and massive destruction should a 7.2-magnitude earthquake hit Metro Manila. The study also contains priority actions that should have been undertaken three to six years after the study was publicized to reduce the impacts of such a strong tremor,” Legarda said.
She said the study showed that a 7.2 magnitude earthquake in Metro Manila is likely to destroy 40 percent of residential buildings and 35 percent of public buildings and kill 34,000 people and injure 114,000 more. Resulting fires can cause 18,000 more deaths.
“We must also ensure that there are back-up systems of vital utilities such as electricity and telecommunications equipment, which are necessary for post-disaster efforts,” Legarda said.
Measures that the government should undertake include promotion of disaster-resilient urban development, ensuring the structural integrity of buildings and critical infrastructure, identifying open spaces for evacuation when tremors occur, and formulating emergency supply system for water, food and other necessities.
“Disaster prevention is a tall order, but it is one well worth the investment. We must prepare ourselves for more frequent natural hazards, keeping in mind that it is only through effective preventive measures that we can save lives,” Legarda said.
