What kind of faults most commonly produce tsunamis?

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

Answer: (B)

When a tsunami forms, the crucial factor is rapid vertical movement of the ocean floor, which suddenly displaces a huge amount of seawater. This vertical uplift happens most strongly at subduction zones where one tectonic plate is pushed over another, generating a thrust (reverse) fault. The sudden uplifting of the seabed along a reverse fault kicks water upward and outward, creating a tsunami that can propagate across entire ocean basins.

Normal faults involve extension and tend to cause vertical motion that is not as large or as sea-floor–uplifting as megathrust events, so they are less effective at generating giant tsunamis. Strike-slip faults move mostly horizontally, producing little vertical displacement of the sea floor, and oblique-slip faults have some vertical movement but not the dominant, large-scale uplift seen in subduction-zone earthquakes.

So, the fault type most commonly producing tsunamis is the reverse (thrust) fault associated with subduction zones.