The Philippine Fault Zone has been active for the past 100 years, marked by several destructive earthquakes such as the Luzon earthquake with a magnitude of 7.7.  

The two most common faults are the West Valley Fault System and the Philippine Fault Zone 

The Philippines is home to about 30 active fault systems capable of generating earthquakes.

Most earthquakes are associated with volcanic eruptions while others occur when some form of energy stored in the earth's crust is suddenly released. 

Geologist use the angle of the fault  which they call slip to describe the steepness of a fault plane.

The fault plane is the surface along which the plate breaks and slides

Faults can be visible on the surface of the crust or it can be underground.

The slip is an angle used to specify the orientation of the fault.

A strike-slip fault  is right-lateral if the hanging wall moves to the left.

Faults are considered inactive if they have been dormant for millions of years or have only experienced large earthquakes once in thousands of years.