Which Fault Moved in the Northridge Earthquake?
ES1010  Types of Faults

Two types of faults are responsible for earthquakes. Surface faults are those that break the ground surface, revealing how the rocks' original position was offset. Blind thrusts are faults that do not reach the surface: rocks move relative to one another on a fault surface beneath the surface, but they only bend overlying rocks and no offset is seen at the surface.

There are three types of surface faults—normal, reverse, and strike-slip. Reverse faults that have a shallow dipping fault plane (slanted only slightly instead of at a steep angle) are called thrust faults. Blind thrust faults are a type of reverse faults.

  !   Click the dots next to the labeled faults to see images and animations of the different types of faults.

Southern California Earthquake Center

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