The tectonic plates (lithospheric plates) that form the outer layer of our planet are variably under pressure from the Earth's molten core and the gravitational forces exerted by the moon and the larger planets. The entirety of the Philippine Islands was created by the collision of the Sunda Plate (a minor extension of the Eurasian Plate) and Philippine Plate (central and southern Luzon lie on the Sunda Plate while the Philippine plate extends along the Eastern seaboard), the latter being influenced by the much larger Pacific Plate, farther to the East. Tectonic plates typically slip over or under or along each other at a rate of 2-5cm per year. The Valley Fault System is a dominantly right-lateral strike-slip fault system in Luzon, Philippines.

Areas close to the edges of the plates become deformed by the movement of these huge sections of the Earth's crust; fault lines are created as these adjacent parts of a plate become deformed and crack. Similar to the tectonic plates, these fault lines (cracks) slip some small amount each year but, sometimes, the underlying rock is so tough that it temporarily prevents movement and so pressure builds up. Eventually the pressure is so great that movement can no longer be prevented and the fault line will slip with a jolt: an Earthquake. Such an earthquake may last anywhere from a few seconds to a minute or more, depending on how much pressure has been built up and how far the crack needs to move before the pressure is released.