How effective are earthquake early warning systems?
Earthquake early warning detection is more effective for minor quakes than major ones.
This is according to a new study from the United States Geological Survey.
Seismologists modelled ground shaking along California's San Andreas Fault, where an earthquake of magnitude 6.5 or more is expected within 30 years.
They found that warning time could be increased for residents if they were willing to tolerate a number of "false alarms" for smaller events.
This would mean issuing alerts early in an earthquake's lifespan, before its full magnitude is determined. Those living far from the epicentre would occasionally receive warnings for ground shaking they could not feel.
"We can get [greater] warning times for weak ground motion levels, but we can't get long warning times for strong shaking," Sarah Minson, lead author of the study, told BBC News.
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