Previous research has shown that the magnitude 9.0 Tohoku quake that struck Japan in 2011 was powerful enough to slightly alter the affected area’s pull of gravity. On the ground (where the gravitational shifts are barely noticeable), it took 3 hours for the Japan Meteorological Agency to gauge its true size, after initially estimating it to be magnitude 7.9.
The new study suggests gravity signals, travelling at more than 185,000 miles per second, were most apparent at monitoring stations between 1,000 and 2,000 km from the quake’s epicentre. At that speed, the signals had enough time to be recorded before the seismic waves took over.
Japan’s largest recorded earthquake, the Tohoku event triggered a tsunami that resulted in over 15,000 deaths and caused the Fukushima Daiichi power plant meltdown — the ongoing cleanup of which is estimated to take between 30 to 40 years. Although we’re still no closer to predicting earthquakes, the researchers claim that (with revision) their method should work for detecting quakes of magnitude 8.5 or greater, which are large enough to generate measurable gravity signals.