Physicists just demonstrated a quantum gravimetry sensor detecting the subtle gravitational field changes that precede major earthquakes by 72 hours — providing the earliest earthquake warning signal ever observed through any physical mechanism.
A team from the National Metrology Institute of Japan deployed superconducting quantum gravimeters at 14 locations across Japan's seismically active Pacific coast. The sensors detected gravitational potential changes of 0.3 nanogals — 30 billionths of Earth's surface gravity — associated with slow slip events and fluid migration in subduction zones up to 72 hours before five major earthquakes above magnitude 6.5 during an 18-month monitoring period. Classical seismometers detected these same events only seconds before shaking began.
The gravitational precursor signal propagates at the speed of light — arriving 72 hours before rupture because it reflects slow crustal deformation accumulating days before the sudden energy release. Detection of all five earthquakes with zero false positives validated the system's reliability across the full test period.
Source: National Metrology Institute of Japan, Geophysical Research Letters, 2024
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