Given that the Philippine archipelago is sandwiched in between two opposite plates - that of the Eurasian Plate (South China Plate) and that of the Philippine Sea Plate, earthquakes are quite common in the country, and its people are very much aware of how devasting the effects of a particularly strong one is.
Now although it is impossible to predict when the next earthquake may occur, scientists can pin down what is called a recurrence interval, which is the average time span between the occurrence of earthquakes. Four major earthquakes have been determined to have taken place for the West Valley Fault in the last 1,400 years. With the recurrence interval at 400 to 500 years and with the last major earthquake originating from the fault was recorded in 1658 or 357 years ago, this means that it may be time soon - perhaps in this lifetime, for another major movement in the fault.
With two very recent consecutive quakes recorded at 6.1 and 6.4 respectively, the Philippines is on edge while they wait, with extreme apprehension and anxiety, for what they call the "Big One".
In a joint study with the Metropolitan Manila Development Authority (MMDA) and the Japan International Cooperation Agency (JICA), Phivolcs looked at 18 earthquake scenarios. Three scenarios for detailed damage analysis were presented: a 7.2-magnitude earthquake from the West Valley Fault, an offshore 7.9-magnitude earthquake from the Manila Trench and a 6.5-magnitude earthquake hitting Manila Bay.
The movement of the West Valley Fault, a 100-kilometer fault that runs through six cities in Metro Manila and nearby provinces, is considered the worst-case scenario and with this, they are anticipating a 'disaster of never-before-seen proportions'.
A magnitude 7.2 earthquake that lasts for at least 30 seconds in the West Valley Fault may lead to the death of 34,000 people. That staggering estimate does not take into account the toll from other disasters that may follow, like fires.
According to the Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS), a 7.2-magnitude earthquake from the West Valley Fault will result in the collapse of 170,000 residential houses and the death of 34,000 people. Injured individuals are estimated to reach 114,000 while 340,000 houses will be partly damaged.
Damages to infrastructures such as bridges, water pipes, electrical and communication are quite pronounced
First responders will be unable to get through the streets and bodies will be lined along the road. The scenario is reminiscent of the horrors of Supertyphoon Yolanda.
The destruction, together with the losses that the economy will suffer, will constitute a national crisis, the study said.
This paints an extremely grim picture though it may also have served as a warning to the authorities to improve risk reduction and management systems.