What kind of faults are most common at convergent boundaries?

• A. Normal faults
• B. Reverse faults
• C. Strike-slip faults
• D. Oblique-slip faults

Answer: (B)

Compression at convergent boundaries squeezes the crust, so the rocks shorten rather than stretch. The way this shortening is accommodated is most effectively by a reverse fault, where the hanging wall moves up relative to the footwall. When the fault dips at a low angle, it becomes a thrust fault, a common feature in mountain belts and subduction zones where large amounts of crust are shortened. This is why reverse (and thrust) faults are the typical faulting style at convergent margins.

Normal faults, by contrast, form under extensional stress when the crust is being pulled apart, so they’re characteristic of divergent boundaries or rift zones. Strike-slip faults arise from shear sliding motion along nearly vertical planes, typical of transform boundaries where plates slide past one another. Oblique-slip faults can occur in various settings, including convergent margins, but they are not the dominant mode of faulting there.