Elasticity

According to the above example, we explain what occurred to a pencil while strength is imposed of both its end. The first symptom of the strength on the pencil is the pencil beginning to bent .This represents that it has elastic properties. This property show that for example the pencil can be deformed or can change its shape and it can return to its essential form while the power on it become decreased. Similar a rubber band or like the pencil, rocks have elastic properties. While a force like compression is imposed to rocks it causes pushing, twisting, pulling of the rock's structure and texture.

 All material among rocks own elastic properties. Any excessive strength would lasting deformation in the object's form.

 Before breakage of object, it is called "elastic limit" In plastic deformation, the object (or rock) would breaks at its elastic limit before any plastic deformation happens. As you know, there are some general changes in situation or some displacement  when a material like the pencil or rubber bend, during elastic properties till it breaks. After some breakage and cracks happened in some part of the object, the object return to its essential form. So in this stage we have "elastic rebound". In the course of an earthquake, seismic waves represent this kind of rebound.