How much time does on-site early earthquake detection usually give if a population is directly above it?

I hope some of you may be able to answer, but I was wondering how much time ON-SITE early earthquake warning systems would give ahead of time before impact if the city was above the active seismic fault?

Update:

Earthquake Early Warning is a thing and is being used in countries like Mexico, Japan and Taiwan for short-term notification on earthquakes.

2 Answers

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  • 1 month ago

    the problem is, there are no such systems, so guessing how they would perform is futile.

    • Mark1 month agoReport

      It exists, its just fairly new, and was able to warn cities of an impending earthquake, just at a small period of time (seconds to minutes). Some of the countries that have this are Japan, Taiwan and Mexico. Mexico was even able to receive a 74 second warning before the earthquake happened.

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  • ?
    Lv 7
    1 month ago

    Earthquake detection is still a very new science. Part of the problem is, each earthquake is different, amd the really big ones often give little to no warning. Theres just a slow, steady building of pressure on the fault over a period of years or decades, then a sudden release of energy all at once

    • Mark1 month agoReport

      It is at that release of energy when the system does its job, because both p waves and s waves are generated, p-waves which are less destructive but go ahead of the s waves are detected first by the system's seismometers, and it warns places that the s-waves (typical shaking) are soon to arrive.

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