|Marikina Valley Fault System|
|Named by||Philippine Institute of Volcanology and Seismology|
|Coordinates||14°38′N 121°5′E / 14.633°N 121.083°ECoordinates: 14°38′N 121°5′E / 14.633°N 121.083°E|
|Region||Central Luzon, Metro Manila, Calabarzon|
|Cities||West: Marikina, Quezon City, Pasig, Makati, Taguig, Muntinlupa, General Mariano Alvarez, Carmona, Silang, San Pedro, Biñan, Santa Rosa, Cabuyao, Calamba|
East: Rodriguez, San Mateo
|Segments||West Valley Fault, East Valley Fault|
|Length||146 km (91 mi)|
|Displacement||10–12 mm (0.39–0.47 in)/yr|
|Plate||Philippine Sea Plate and Sunda Plate|
|Volcanic arc/belt||Macolod Corridor|
The Marikina Valley Fault System, also known as the Valley Fault System (VFS), is a dominantly right-lateral strike-slip fault system in Luzon, Philippines. It extends from Doña Remedios Trinidad, Bulacan in the north and runs through the provinces of Rizal, and the Metro Manila cities of Quezon, Marikina, Pasig, Makati, Taguig and Muntinlupa, and the provinces of Cavite and Laguna that ends in Canlubang.
The fault contains two major segments, known as West Valley Fault (WVF) and East Valley Fault (EVF).
The west segment, known as the West Valley Fault (WVF), is one of the two major fault segments of the Valley Fault System which runs through Metro Manila to the cities of Marikina, Quezon City, Pasig, Makati, Taguig and Muntinlupa and moves in a dominantly dextral strike-slip motion. The West Valley Fault segment traverses from Doña Remedios Trinidad to Calamba with a length of 129.47 kilometers (80.45 mi).
The West Fault is capable of producing large scale earthquakes on its active phases with a magnitude of 7 or higher.
The eastern segment, known as East Valley Fault (EVF), moves in an oblique dextral motion. It extends to about 17.24 kilometers (10.71 mi) from Rodriguez to San Mateo in the province of Rizal.
See also: List of earthquakes in the Philippines
Based on kinematic block models that utilize GPS, actual fault geometry, and earthquake focal mechanisms, the West segment of the Marikina Fault was resolved to be almost fully locked, meaning it is currently accumulating and loading elastic strain, at the rate of 10 to 12 mm/yr. The fault possesses a threat of a large scale earthquake with an estimated magnitude between 6–7 and as high as 7.6  to Metro Manila and surrounding provinces with death toll predicted to be as high as 35,000 and some 120,000 or higher injured and more than three million needed to be evacuated.
99 private villages and subdivisions inside 80 barangays are traversed directly by the fault and endangers 6,331 buildings in a span of 2,964.10 square kilometers (1,144.45 sq mi), to where majority are houses with 19 schools included in the list.
There are about 6,331 structures that are directly above the Valley Fault System within a 10-meter proximity which would be in potential danger of destruction once the slip-fault moves. This sums up to an area of 2,964.10 square kilometers in danger of collapse.
If a major earthquake were to hit Metro Manila today, the devastation would be so big even disaster response authorities cannot simply cope with it. And it even looks like disaster preparedness occupies a low priority among officials down to the municipal level.
Is Metro Manila prepared for the Big One?
The United Nations is advising the Philippines to be ready for an upcoming big earthquake. A quake with a magnitude of 7 or higher on the Richter scale is sure to hit Metro Manila, they say, but the bigger question is when exactly this will happen.