To decide how much action is required to reduce earthquake hazards, you must estimate your risk. These are difficult questions. The sections on the following pages are designed to help you assess your risk from earthquakes and determine how much action is appropriate for you. We can live more safely with earthquakes by understanding the risks and by taking reasonable precautions. Duration of shaking.
Duration depends on how the fault breaks during the earthquake.
The strongest shaking during the 1964 earthquake lasted 3 to 4 minutes. During a magnitude 7 earthquake, the shaking may last 30 to 40 seconds. The longer buildings shake, the greater the damage. Strength of shaking. Many damaging earthquakes occur within 15 miles of the Earth's surface.