(CN) – A strong earthquake might feel frightening to anyone caught in the middle, but a study from researchers in quake-prone Tokyo say new sensors originally meant to observe the gravitational waves from the Big Bang could one day be used to give people as much as a 10-second warning before a temblor hits.
Modern early-warning detection networks are made up of devices that measure motion on the ground. But because the sensors move along with the instrument, subtle signals from earthquakes aren’t picked up.
A physics paper from the Istituto Nazionale di Fisica Nucleare in Italy on an unrelated topic provided researchers a germ of an idea: A device that measures the strength of local gravity – a gravimeter – could theoretically detect earthquakes.
Associate Professor Shingo Watada from the Earthquake Research Institute from Tokyo University said if a gravimeter and sensors used in modern detection networks could pick up enough data from a big earthquake, researchers could learn to detect earthquakes with both devices and compare the two.
“This could be an important tool for future research of seismic phenomena," said Watada.
Earthquakes are the result of a tectonic plate shifting below the earth’s surface at a single point, which then sends out seismic waves that radiate at 6 to 8 kilometers per second. That transmits energy and rapidly alters the density of the area just below the surface as the seismic wave passes through.
As the gravity spreads from the origin of the tectonic plates at light speed, gravimeters could pick up on this change in density ahead of the actual seismic wave that would normally be felt by seismic sensors.
The deadly 2011 Tohoku earthquake in eastern Japan lasted for six minutes and registered as a magnitude 8.9, but the event was also the genesis of the paper released by researchers from the University of Tokyo.
Earthquake Research Institute postgraduate Masaya Kimura said, “Our approach is unique as we examined a broader range of sensors active during the 2011 earthquake. And we used special processing methods to isolate quiet gravitational signals from the noisy data.”
Kimura told Courthouse News the study reviewed data from gravimeters, seismometers – which measure motion on the ground – and meters that measure ground tilt.
Researchers used this range of seismic data from across the region, including sensors on land and at sea in multiple locations. From their models, researchers were able to get an accurate reading that has a one-in-a-trillion chance of being incorrect.
The data could one day be used to calibrate future detection devices. Associate physics professor Masaki Ando from Tokyo University has already put together a prototype gravimeter, called the TOBA.
Researchers say the TOBA devices will be able to get accurate readings despite movement within and around device, as it senses dips in gravity.
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