Do faults break all at once, or in many short segments?


     • Spaghetti Asperity
Related Animations
     • Elastic Rebound in a Strike-slip Fault
     • Elastic Rebound in a Subduction Zone


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Multiple Asperities on a Strike-Slip Fault Plane


Oblique view of a right-lateral strike-slip fault with multiple asperities. When one asperity slips, there is an added load on the adjoining asperities. In a large earthquake there is a cascading effect as each zone that slips loads the next zone, which then slips, and so forth, sometime for hundreds of miles, in a process that can continue for 5 or more minutes. Narration by John C. Lahr taken from the "Spaghetti Vice" video lecture below.


Quicktime (1.4 MB)

Simple Models of Fault Movement with Single Asperity, High Friction, and Little or No Friction

Single Asperity Along Fault Zone

View looking into a fault zone with a single asperity. Regional right lateral strain puts stress on the fault zone. A single asperity resists movement of the green line which deforms before finally rupturing.


Quicktime (420 kB)

Low-friction Fault Zones


View looking into right- and left-lateral fault with low friction along fault contact. There is no deformation of the rock adjacent to contact.

Quicktime- Left Lateral (260 kB)

Quicktime- Right Lateral (260 kB)

John Lahr Demonstrates Asperities Along a Strike-Slip Fault

Quicktime (3.7 MB)

Animations and videos are made in partnership with Earthscope, USGS, and Volcano Video & Graphics.

Please send feedback to Jenda Johnson.