Which of the following is NOT a primary effect?

• A. Ground shaking
• B. Landslide
• C. Death
• D. Road/bridge destruction

Answer: (B)

The main idea is distinguishing between primary effects and secondary effects of an earthquake. Primary effects are the immediate, direct results of the seismic energy hitting the ground—most notably ground shaking and the initial damage caused by that shaking. Secondary effects arise because the ground has been disturbed, leading to things like landslides, liquefaction, tsunamis, and fires.

Landslides are caused by the shaking destabilizing slopes, but they occur as a consequence of the initial shaking rather than as the direct energy impact itself. That makes them a secondary effect. Ground shaking is a primary effect because it is the direct action of the earthquake on the ground. Destruction of roads and bridges and potential death from collapsing buildings are also direct outcomes of the shaking, so they are primary effects.