What factors influence the intensity and destructiveness of an earthquake in a given city?

• A. Magnitude alone determines intensity.
• B. Only the depth of the earthquake matters.
• C. Magnitude, depth, distance to epicenter, local geology and soil amplification, building design and construction quality, duration, and depth to groundwater.
• D. Tectonic plate type is the sole factor.

Answer: (C)

Shaking intensity and the resulting damage in a city come from a combination of factors that affect how ground motions arrive and how structures respond. The energy released by the earthquake depends on magnitude and depth, but how strong the shaking feels at a city also depends on how far the city is from the epicenter. Waves lose energy as they travel, and path effects—like the type of rocks they pass through—shape the frequency and amplitude of ground motion that reaches urban areas.

Local geology and soil conditions matter a lot: soft soils, sediments, and basins can magnify shaking and change its duration, so a city built on such materials may experience stronger and longer shaking than one on solid bedrock. The design and construction quality of buildings and infrastructure determine how well they resist those motions; well-designed structures can withstand shaking better, while poorly built or non-retrofitted buildings are more vulnerable to damage. Duration of shaking also plays a role—longer shaking means more cycles of stress in structures and more potential for failure. Groundwater depth influences liquefaction risk, where saturated soils lose strength during shaking, leading to ground failure and additional damage.

All these factors together explain why intensity and destructiveness vary from one city to another. The other options miss key elements—relying on magnitude alone ignores how distance, geology, site conditions, building quality, shaking duration, and liquefaction potential shape actual damage.