A vibration detection device that triggers elevator shutdown and returns cars to the nearest floor when earthquake motion is detected.
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Seismic sensors in elevator systems detect ground acceleration or vibration caused by earthquakes and trigger automatic safety responses. Upon detection above a set threshold (commonly 25–80 gal, depending on seismic zone and standard), the elevator completes its current move then proceeds to the nearest floor, opens its doors, and shuts down to prevent passenger entrapment and rope derailment that could occur during strong shaking. Some systems distinguish between P-waves (primary, less destructive) and S-waves (secondary, more damaging) to allow a brief window to return cars to a floor before the stronger shaking arrives. Required by ASME A17.1 in seismic zones 2 and above, and referenced in JIS A4306 in Japan.
