Where does the stress build-up and eventually released within a fault?

Fault is formed because of tensional movement by endogenetic forces comes from inside of the earth.

Explanation:

Rocks in crust are displaced due to tensional movement by endogenetic forces. Faults are in different types such as Normal fault, reverse fault, lateral fault and step fault. Rift valley and graben are the landform which caused by the faults and folds. In tensional movement, both the peripheral rocks are acted under the tensional stress, then that tensional stress exceeds the elasticity of rock crust which ultimately broke and middle portion of landmass become down thrusted.

answer; the nazca plate is converging with the south american plate

a substance in a physical state in which it does not resist change of shape and will expand indefinitely to fill any container.

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