Once again, turn on this function on your phone, it can save lives at critical moments →

At present, earthquake relief work in Gansu and Qinghai is being carried out in an intense and orderly manner. When the earthquake occurred, many cities such as Xi'an, Lanzhou, and Yinchuan felt the tremors, and some citizens received earthquake warnings on their mobile phones in advance. The earthquake warning function is very important. In an emergency, a few seconds of advance warning is precious time for emergency avoidance.

Image source: Tuchong

01 The principle of earthquake early warning : getting ahead of the S wave

When an earthquake occurs, two types of body waves are generated inside the Earth:

▶P wave: compression wave, the particle vibration and propagation direction are consistent, when it arrives, people feel close to shaking up and down; P wave runs fast, propagating about 6 kilometers per second;

▶S wave: also known as shear wave, the particle vibration direction is perpendicular to the propagation direction, and when it arrives, people feel close to horizontal shaking; S waves travel slowly, propagating about 3.5 kilometers per second. However, the S wave vibration amplitude is larger, and the energy it carries is several to dozens of times that of the P wave. Its horizontal shear effect is an important factor in causing structural damage.

If we can warn the public of the possible magnitude or potential damage of earthquakes in the form of an alarm before the S wave carrying more energy arrives, or even before the P wave arrives a few seconds after an earthquake, the public can obtain emergency escape time, and high-speed railways, hazardous chemical companies, hospital operating rooms, etc. can take earthquake emergency measures in advance, thereby reducing casualties and social property losses . This is what we call earthquake early warning.

02Can earthquake early warning save lives?

Theoretical studies on the disaster reduction effect of earthquake early warning have shown that a warning time of 3 seconds can reduce casualties by 14%; if it is 10 seconds, the casualties can be reduced by 39%; and if the warning time is 20 seconds, the casualties can be reduced by 63%.

Therefore, earthquake early warning can effectively reduce casualties .

03What should you do after receiving an earthquake warning?

▶For the public, according to the warning time and their own location, they should take reasonable risk avoidance measures and evacuate effectively and quickly.

▶For engineering projects, urgent emergency measures can be taken according to the warning time.

04Is there a blind spot in earthquake early warning?

There is a blind spot, with the epicenter of the earthquake as the center and a radius of 21 kilometers, which is a blind spot for early warning. People in the blind spot will feel the shaking first, and then hear the warning alarm.

The effective range of earthquake early warning is 21 kilometers to 200 kilometers, but there is almost no shaking beyond 200 kilometers.

05 How are earthquake early warning signals issued?

Earthquake warning signals are mainly released through mobile phones and televisions. Citizens who have activated mobile phone and television warning services can receive warning signals.

For the industry, you can install a professional earthquake early warning terminal to enjoy earthquake early warning services.

06 Teach you how to turn on the earthquake warning function on your phone in 10 seconds

Image source: Ministry of Emergency Management Weibo

Source: Science Popularization China Comprehensive Xinhua News Agency, Science and Technology Daily, China Earthquake Networks Center, Safe Beijing, Ministry of Emergency Management, etc.