App alerts users of real-time seismic activity, giving residents time to flee

Liu Qi, a young office worker in Chengdu, Sichuan province, heard his smartphone buzzing and saw a countdown begin from 69 to zero at 9:23 am on Monday.

A second later, he saw a pop-up on the phone reporting that seismic waves would arrive in 68 seconds. The pop-up also showed a magnitude 4.1 earthquake was taking place in Changning, Sichuan, and the epicenter was 257 kilometers away.

"As the earthquake did not cause any trembling in the office, I did not leave it," he said.

Liu had installed an early earthquake warning application on his phone from the Institute of Care-Life in Chengdu. When the phone started the countdown from 69, it meant seismic waves from the epicenter would hit Chengdu in 69 seconds.

Sixty-one seconds before the waves reached Chengdu on June 17, when a magnitude 6.0 earthquake struck Changning, local residents had received the early warning that seismic waves from Changning were impending through smartphones, radio, television, government microblog and special receiving terminals.

A real-time system providing warnings seconds after a quake can save lives because the warnings are transmitted via radio waves traveling faster than seismic waves. Radio waves travel at 300,000 km per second, while seismic waves travel at 3 to 6 km/s. Therefore, people in nearby areas may escape before seismic waves arrive, said Chen Huizhong, a senior research fellow with the Institute of Geophysics under China Earthquake Administration.

China only started attaching importance to early warnings after the Wenchuan earthquake, he said. That quake, a magnitude 8.0 temblor in Sichuan, killed 69,226 people in 2008.

After the Wenchuan quake, Wang Tun, a postdoctoral fellow of theoretical physics at the Austrian Academy of Sciences, set up the Institute of Care-Life to study the early warning system.

The institute succeeded in providing an early warning for a destructive magnitude 4.9 earthquake in Qiaojia, Yunnan province, in February 2013. It was China's first successful early warning of a destructive earthquake, Chen said.

Since then, Wang's institute has sent correct early warnings after 53 quakes above magnitude 4.5, including the magnitude 7.0 earthquake in Lushan, Sichuan, in 2013; the magnitude 6.5 earthquake in Ludian, Yunnan, in 2014; and magnitude 7.0 earthquake in Jiuzhaigou, Sichuan, in 2017.

The institute's system - which has been installed in 31 provincial-level regions and covers 660 million people in an area of 2.2 million square kilometers - is the world's largest early earthquake warning network.

China is the third country to have an early earthquake warning system, after Mexico and Japan. In 2015, Nepal became the fourth country to own it after Wang's institute established it there 100 days after the magnitude 7.8 Nepal earthquake, which killed 8,699 people. The system covers one-third of Nepal.

The Nepal earthquake's epicenter was about 90 km from Kathmandu, the capital. People there would have been warned 18 seconds before seismic waves arrived had such a system been in place, and thousands of lives could have been saved, said Jiba Raj Pokharel, a leading official from the Nepal Academy of Science and Technology.