An asperity (is an area on a fault that is stuck or locked. In the Earth, tectonic earthquakes are caused by slip along a fault Earthquake Resources movement involves slip on one or more asperities, or “stuck patches” where the friction is highest. Most of the energy that is released by earthquakes comes from the patches that become “unstuck.
Scrap lumber, raw spaghetti, and a ratcheting bar-clamp can be combined to create a physical model of asperities on a fault. In the model the wood represents the fault, the spaghetti represent asperities or stuck patches on the fault, and squeezing the clamp represents tectonic forces. As you slowly apply stress with the clamp, a few spaghetti strands may break (foreshocks) a few seconds prior to many strands breaking in rapid succession (mainshock). This event may be followed by a few remaining strands breaking (aftershocks).
Students will be able to:
- Use the asperity vice to demonstrate and explain asperities on a fault
- Explain the concepts foreshock, mainshock, and aftershock