Which of the following is NOT a type of stress found to produce earthquakes?

• A. Flow
• B. Tensile
• C. Shear
• D. Compression

Answer: (A)

Earthquakes arise when rocks accumulate elastic stress and fail suddenly along faults. The stresses that commonly drive brittle failure and earthquake release are three clean types: compression (pushing rocks together), tensile or extension (pulling rocks apart), and shear (sliding past each other). These are the forces that make rocks crack and snap, releasing energy that we feel as earthquakes.

Flow, by contrast, is a different way rocks can deform. It describes ductile movement where rocks deform plastically and smoothly under high temperature and pressure, rather than breaking suddenly. This kind of deformation doesn’t produce the rapid energy release characteristic of earthquakes, which is why flow is not considered a type of stress that produces earthquakes.