The 20-second warning time is referenced for which region?

The 20-second warning time is referenced for which region?

• A. Los Angeles Basin
• B. Seattle area
• C. San Francisco Bay Area
• D. Phoenix region

Answer: (C)

Understanding this question relies on how earthquake early warning works. P-waves arrive first and travel faster, while S-waves cause the shaking we feel. The amount of warning time you can get depends on how far away the earthquake source is from your location. In many educational examples, the San Francisco Bay Area is cited as having about a 20-second lead time, because a large earthquake on nearby regional faults would produce enough separation between the initial P-wave detection and the onset of stronger shaking at Bay Area sites for roughly twenty seconds of warning. This makes the Bay Area the region associated with that 20-second reference. Other regions would have different typical lead times depending on how distant a potential quake is from them.

Understanding this question relies on how earthquake early warning works. P-waves arrive first and travel faster, while S-waves cause the shaking we feel. The amount of warning time you can get depends on how far away the earthquake source is from your location. In many educational examples, the San Francisco Bay Area is cited as having about a 20-second lead time, because a large earthquake on nearby regional faults would produce enough separation between the initial P-wave detection and the onset of stronger shaking at Bay Area sites for roughly twenty seconds of warning. This makes the Bay Area the region associated with that 20-second reference. Other regions would have different typical lead times depending on how distant a potential quake is from them.