WEST VALLEY FAULT

West Valley Fault

Running Through Bulacan, Rizal, Metro Manila, Cavite, and Laguna. Those near the West Valley Fault will first feel an up and down motion, followed by a horizontal ground motion. Those farther from the West Valley Fault will only feel a horizontal ground motion. The West Fault is capable of producing large scale earthquakes on its active phases with a magnitude of 7 or higher and moves in a dominantly dextral strike-slip motion

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 Marikina Valley Fault System is considered to be almost fully locked, i.e. almost no movement, so the pressure is building all of the time

When the West Valley Fault moved and generated a 7.2 magnitude earthquake, 34,000 people may die and will damage lifelines including water, infrastructure, roads, ports, and telecommunication.

The concentration of population in Metro Manila along with the various non-engineered and non-earthquake resilient infrastructures and buildings are causative factors.

East Valley Fault

The eastern segment, known as East Valley Fault (EVF) moves in an oblique dextral motion.[2] It extends to about 17.24 kilometers (10.71 mi) from Rodriguez to San Mateo in the province of Rizal.[1]

Recorded Earthquakes

• In July 1990, the Central Philippine Fault moved and caused the 7.7 magnitude earthquake that wreaked havoc across Luzon.

• In February 2006, after a 10-day continuous downpour, a minor movement of the same fault, a 2.6 magnitude earthquake tripped a saturated cliff of a ridge that caused a massive rock slide-debris avalanche burying the entire village of Guinsaugon, a township of St. Bernard in Southern Leyte. More than a thousand death was recorded including the 247 children and 7 teachers who died when a school was entombed by the landslide.

Risks

In a 2011 a report by the Earthquakes and Megacities Initiative ("EMI") estimated that a magnitude 7.2 Richter earthquake occurring within the Marikina Valley Fault System would severely damage 175,000 buildings, cause 33,500 deaths, with 114,000 injured and 3,000,000 needing evacuation due to unsafe buildings. Metro Manila has grown significantly in size since 2011 and a significant portion of that development has been close to the West Valley Fault, so these estimates could possibly be doubled.