Earthquake warning alerts Chengdu residents a minute before shaking starts

China claims to be the third country with an earthquake early warning system, after Japan and Mexico

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“The earthquake S-waves are arriving in 45 seconds!” reads a message that appeared on a Weibo user’s TV screen. (Picture: Wang-Qiuyan via Weibo)

Published: 10:27pm, 18 Jun 2019Updated: 9:07am, 20 Sep 2019

This article originally appeared on ABACUS

Sixty-one seconds before residents in Chengdu felt the shaking caused by a 6.0 magnitude earthquake, many people were alerted to the upcoming tremors by a countdown from loudspeakers in their neighborhood. A “di di” sound that rang out each second accompanied the announcement warning of the earthquake already happening 261 kilometers (162 miles) away.

Some also saw messages that popped up on TV screens, which included the magnitude of the quake and the time left before it arrives.

These are all part of an earthquake early warning system developed by the Institute of Care-Life, a research lab founded in Chengdu in the wake of the 2008 Sichuan earthquake that killed more than 87,000 people. The system, named ICL, has been in use since 2013, and it has successfully warned of several major quakes in Sichuan and Yunnan provinces.

The system is similar to those already commonly used in seismically active countries like Japan and Mexico. When an earthquake occurs, two types of waves shoot out from the epicenter: The faster but mild P-waves, and the slower but stronger and more damaging S-waves.

P-waves are the first to reach the sensors deployed across the landscape, and the data is almost instantaneously sent to alert centers before appearing on people’s devices. This gives people some time to react before the S-waves arrive.

The system is still not well known in China. On social media, many people said they were impressed by the system, but many others said they were initially confused by the sound of the countdown.