Scientists reported that they have detected a signal faster than seismic waves in sending out warning that an earthquake is on its way.
In a study published in the journal Nature Communications, the researchers described a method that involves tracking the subtle changes in Earth's gravity that immediately occur after an initial rupture.
The researchers studied the 2011 Tohoku-Oki earthquake in Japan and found that gravity signal can indicate that a tremor is on its way and it is faster than seismic waves.
Subtle Changes In Gravitational Pull
Earlier research showed that there are subtle changes in Earth's gravitational pull around an earthquake's epicenter which can be attributed to the changes in the density of the rock in the area. Scientists, however, were not certain if these changes can be picked out amid background noises such as the rising and dropping of the tide.
For the new study, researchers looked at the data from gravity sensors located some 500 kilometers away from the epicenter of the earthquake and then compared these with data from other seismic stations in the same area.
After looking at measurements taken over a period of 60 days prior to the earthquake and the data from the day prior to, day of and the day after the earthquake, they found a small blip that stood out enough to confirm that an earthquake had occurred.
Small Gravitational Signal Occurred Earlier Than Seismic Wave
The researchers also found that the signal that hit the gravimeters arrived about nine seconds earlier than the seismic waves.
The findings may potentially help researchers design faster and more powerful earthquake warning technologies that are better than early warning systems currently in use. Current methods rely on detecting seismic waves.
Knowing that an earthquake is on its way would offer automated systems a few extra seconds to shut down, which can possibly save lives. Five to 10 seconds could be crucial for programs that would stop a heavy machinery, elevators and trains.
For now though, scientists are faced with the challenge of developing new instruments to better detect gravity signals.
"The robust detection of transient gravity signals by a network of such instruments has the potential to reduce the time required to declare a warning, thus opening new directions in earthquake seismology, enabling faster earthquake magnitude estimation (which currently takes up to several minutes) and complementing earthquake early-warning systems currently based on seismic and geodetic networks," wrote Caltech seismologist Jean Paul Ampuero and colleagues in their study.
