By Brian Campued
The Philippine Institute of Volcanology and Seismology (Phivolcs) stressed that the recent earthquakes in Cebu, La Union, and Davao Oriental have no connection with each other.
In a press conference, Phivolcs Director Teresito Bacolcol noted that the Philippines has 180 active fault segments as well as six trenches, all of which can generate earthquakes.
“Wala po tayong nakikitang pattern, again, these are all normal activities. The Philippines is very much active tectonically,” Bacolcol said.
“There’s always this possibility na magkakaroon ng paglindol [nang] sunod-sunod,” he added, emphasizing that most earthquakes recorded are weak.
The Phivolcs chief also said that the magnitude 7.4 earthquake off the coast of Manay, Davao Oriental on Friday morning was produced by the movement along the sea floor on the Philippine Trench.
“Sa mga trenches kasi ‘yung motion natin would be thrust faulting, may isang block na tumaas unlike sa Bogo City for example, the Bogo Bay fault, it’s mainly horizontal but dito (Philippine trench), it’s vertical,” Bacolcol explained.
“These are all independent earthquake generators—wala pong kinalaman yung Philippine Trench sa Bogo Bay Fault… Yung activity ng isa will not induce the activity of the other one.”
Other trenches in the country are located in Manila with four segments; Negros, Sulu, and Cotabato, all with two segments; and East Luzon with one segment. The Philippine Trench has six segments.
As of 3:00 p.m., 266 aftershocks have been recorded following the powerful earthquake in Davao Oriental. Of this number, 62 were plotted while 11 were felt—with the highest magnitude recorded at 5.8.
Aftershocks may last for several days to several weeks.
In an interview on “Lindol sa Mindanao at Visayas: An Integrated State Media (ISM) Special Coverage” aired over at the People’s Television Network (PTV-4), Bacolcol reminded the public to do the “duck, cover, and hold” during a strong aftershock and immediately evacuate to an open area when the shaking stops.
“Kapag may napansin silang visible damage sa kanilang bahay or sa mga structure kung saan sila namamalagi, huwag muna sila pumasok because structurally compromised buildings should not be reoccupied unless certified safe by their municipal or city engineers,” he said.
“By definition, aftershocks are one magnitude lower than the main shock. So ‘yung aftershock natin at most would just be around 6.4,” he added.
Meanwhile, the tsunami warning issued for all coastal communities in the provinces of Davao Oriental, Dinagat Islands, Surigao del Norte, Surigao del Sur, Leyte, Southern Leyte and Eastern Samar has also been lifted at 1:43 p.m.
“Tandag Surigao del Sur Sea level Monitoring Station for Tsunami Detection has recorded a tsunami wave height of around 30 cm at 10:20 a.m.,” Phivolcs said in its advisory.
Bacolcol explained that as part of their standard operating procedures, two hours are added as buffer time after the 11:43 a.m. end time on the tsunami warning to ensure that there are no more threats to the coastal communities affected.
He also urged the public to stay informed about the natural warning signs of impending local tsunami—a strong shaking, receding of the sea level, and a roaring sound coming from the sea.
“Kahit isa man lang dito sa tatlo yung maranasan while nasa coastal community, then you have to move right away and go to a higher place kasi baka yung babalik no’n ay would be matataas na tsunami waves.” (with report from Rod Lagusad / PTV News)
-jpv
