Thursday, February 9, 2012

Valley Fault System in the Philippines

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As we wait to get the geo hazard map, I will try to present the Valley Fault System in the Philippines as part of shedding light to countless scare messages we all are receiving about great quakes to happen.

When the Valley Fault system in the Philippines move, we will experience shakes. With the Negros quake that devastated areas in the epicenter, many are now scared of the text messages telling predictions of another giant earthquake. Don't be mislead! Earthquake remains to be one of the calamities we are never capable of foretelling, and not even the aftershocks of this Negros quake can be foretold.

So, to my students who would grab their bags and get ready to run out of the room when aftershocks are felt, here is what you need to know about the Valley Fault System in the Philippines.

With our country forming its part in the Asia-Pacific Ring of Fire, earthquake is given. But that isn't the only thing that might cause shakes here. The Philippine Valley Fault System which is an inter-related system of faults throughout the whole of the Philippine Archipelago is the  primarily cause of tectonic forces compressing the Philippines into what tectonic geophysicists call the Mobile Belt of the Philippines. 

The Philippine Mobile Belt is composed of multiple blocks and strips. Most strips like the Zambales ophiolites which is at least 400 km long and 50 km wide  are long and narrow. The strips generally points north-south and the area of convergence are marked by fault lines. 

The tectonic plates compress and lift parts of the Philippines resulting to faulting. The main fault that runs the longest is called the Philippine Fault. In Luzon, as time goes by, it has been noticed that the fault has become stemmed. All faults in the Philippines are interrelated by the tectonic forces influenced by the Philippine Mobile Belt. 

The following are the Active Fault Lines in the Philippines: 

1. Marikina Valley Fault (Montalban-San Mateo-Marikina-Pasig-Taguig-Muntinlupa-S… Pedro-Binan-Carmona-Santa Rosa-Calamba-Tagaytay-Oriental Mindoro)
2. Western Philippine Fault (Luzon Sea-Mindoro Strait-Panay Gulf-Sulu Sea)
3. Eastern Philippine Fault (Philippine Sea)
4. Southern of Mindanao Fault (Moro Gulf-Celebes Sea)
5. Central Philippine Fault (Entire Ilocos Norte-Aurora-Quezon-Masbate-Eastern Leyte-Southern Leyte-Agusan Del Norte-Agusan Del Sur-Davao del Norte)

First on the list, the Marikina Valley Fault System is a group of slip fault which extends from San Mateo, Rizal to Taguig City; running through Makati, Marikina,ParaƱaque, Pasig and Taguig in the Metropolitan Manila Area. 

The fault movement can cause large scale earthquakes with a magnitude of 7 or higher within the Manila Metropolitan Area capable of causing death toll as high as 35,000 and more than three million needed to be evacuated if that ever happens. 

WE better get ourselves armed with information, so we won't panic everytime we receive messages of the "upcoming earthquake" chain messages.  

Here is the map of the Philippine faults from Philvolcs: 

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