Review of Seismology Concepts
Elastic Rebound Theory

Elastic rebound theory states that as tectonic plates move relative to each other, elastic strain energy builds up along their edges in the rocks along fault planes. Since fault planes are not usually very smooth, great amounts of energy can be stored (if the rock is strong enough) as movement is restricted due to interlock along the fault. When the shearing stresses induced in the rocks on the fault planes exceed the shear strength of the rock, rupture occurs.

It follows from this that if rocks along the fault are of a certain strength, the fault is a certain length, and the plates are slipping past each other at a defined rate, it is possible to calculate the amount of time it will take to build up enough elastic strain energy to cause an earthquake and its probable magnitude.

Initial Time

The fence is built straight across the fault trace.

After Several Years

Tectonic movement occurs, but the edges of the crustal blocks are restrained by friction along the fault, and the ground and fence bend. Elastic strain energy builds up.

Following Rupture

The edges of the blocks along the fault try to "catch up" with the middle as they release their strain energy during the rupture, but don't quite make it due to fault drag. Now the fence is offset and slightly curved.