Why did Beijing residents receive an early warning of a 5.5-magnitude earthquake in Pingyuan County, Shandong? What can we do in a few seconds?

At 2:33 a.m. on August 6, a 5.5-magnitude earthquake occurred in Pingyuan County, Dezhou City, Shandong Province, and most areas of Beijing also felt the tremor. After the earthquake, many citizens received early warning alerts on their mobile phones about the arrival time of the earthquake's shear waves and the distance from the epicenter.

Why do we receive such information? Why do different regions receive different information? What can we do after receiving an earthquake warning?

Earthquake warning is not a forecast but an alarm

According to the Beijing Municipal Earthquake Administration, earthquake early warning is not an earthquake forecast, but an alarm. Receiving an early warning message indicates that an earthquake has occurred. It refers to the rapid issuance of a risk avoidance alarm to areas where destructive earthquake waves have not yet reached after an earthquake occurs. It usually lasts only a few seconds to tens of seconds, mainly to buy time for emergency response and evacuation for some special industries and the public.

Specifically, when an earthquake occurs, two main types of seismic waves are generated: a faster but weaker longitudinal wave, and a slower but stronger transverse wave. Earthquake early warning uses the principle that longitudinal waves travel faster than transverse waves, and that electromagnetic waves travel much faster than seismic waves. After an earthquake occurs, seismographs near the epicenter capture longitudinal waves, and use seismic wave information to quickly calculate earthquake parameters and impact, and issue earthquake warnings to areas that may be damaged and affected before the more destructive transverse waves arrive.

The Beijing-Tianjin-Hebei earthquake early warning network has been completed

It is understood that the earthquake early warning network in the Beijing-Tianjin-Hebei region has been completed. After a destructive earthquake occurs, the China Earthquake Early Warning Network will release earthquake early warning information through multiple channels such as emergency broadcasts, mobile phones, televisions, and special terminals, providing users in the target area with emergency evacuation time of several seconds to tens of seconds.

According to the China Earthquake Administration, in recent years, the speed of earthquake early warning information output in China has continued to increase, from manual rapid reporting of about 10 minutes to automatic rapid reporting of 1 to 2 minutes, and then to earthquake early warnings in seconds , providing strong technological support for earthquake relief and disaster relief.

The length of earthquake warning time depends on the distance of the area from the epicenter.

However, earthquake early warning also has limitations.
After the earthquake occurred in the early morning of August 6, many Beijing residents received early warning information, but the content of the early warning was different for residents living in different areas, especially the arrival time of the earthquake shear wave and the distance from the epicenter. It is understood that the length of the earthquake early warning time depends on the distance of the area from the epicenter. The closer the area is to the epicenter, the shorter the early warning time. Generally speaking, near the epicenter, the time for early warning is almost zero, that is, there is an early warning blind spot.

What magnitude of earthquake will trigger earthquake warning in Beijing? Beijing Seismological Observatory previously introduced that if an earthquake with a magnitude of 4 or intensity of 5 or above occurs in Beijing, earthquake warning information will be issued. After receiving it, the general public must remain calm, correctly identify earthquake warning information through pictures, light alarms, sound alarms, voice prompts, etc., and take corresponding risk avoidance measures according to the environment.

▲Earthquake early warning software style diagram (red warning is a red icon, yellow warning is a yellow icon)

Red warning: a destructive earthquake has occurred. The estimated intensity at the location of the warning terminal is 7 degrees or above, and emergency evacuation measures need to be taken. Orange warning: the estimated intensity at the location of the warning terminal is 5 or 6 degrees, and there may be strong shaking, so appropriate evacuation is required. Citizens are requested to take appropriate evacuation measures based on their own environment and remember the correct evacuation posture: lie down, cover, and hold on. Once an earthquake occurs, do not panic and take evacuation immediately.

Regarding the earthquake in Pingyuan County, Shandong, the Beijing Municipal Seismological Bureau made a timely and authoritative announcement early in the morning of August 6: After preliminary analysis and judgment, the earthquake will not have a significant impact on short-term seismic activity in Beijing, and there have been no obvious short-term earthquake anomalies in Beijing recently.

▲Beijing Earthquake Bureau Weibo

How to turn on the earthquake warning function on your mobile phone?

Earthquake warning is so important that many people ask, how can we receive it in the first place? You can check whether your phone has the "earthquake warning" function enabled. Depending on the phone model, some brands of phones require you to search for the keyword "earthquake warning" in the app store and download the relevant APP. Some brands of phones require you to go to the "settings" of the system, find the "security" option, and then turn on the "earthquake warning" function step by step according to the prompts.

How to open it on various mobile phone models:

1. Huawei

Settings → Security → Emergency Warning Notification → Earthquake Warning.

2. Xiaomi

Mobile Manager → Family Care → Earthquake Warning.

3. Glory

Settings → Security → Emergency Warning Notification → Earthquake Warning.

4. OPPO/OnePlus/Realme

Settings → Security → SOS Emergency Contact → Natural Disaster Alerts → Earthquake Alerts.

5. vivo/iQOO

Weather App → Settings → Earthquake Warning → Enable Earthquake Warning Service.

6. Apple/Samsung/other mobile phones

Search the keyword "earthquake warning" and download the relevant app on your own.

In addition, residents in some earthquake-prone areas of China have installed special terminals for earthquake early warning systems in their homes. It is like a small TV screen. Once an earthquake strikes, early warning information such as the countdown to the arrival of the earthquake wave will appear on the screen, reminding users to take shelter quickly.

What can we do after receiving an earthquake warning?

What can we do in the short time window after receiving an earthquake warning? The Chengdu High-tech Disaster Reduction Research Institute provides an escape timetable for reference:

Earthquake early warning and risk avoidance strategies

1. Basic principles: Don’t panic, don’t jump off a building, don’t take the elevator

2. Risk avoidance measures: Reasonable risk avoidance measures should be selected according to the warning time and the time it takes to avoid danger to the nearest safe place.

3. Risk avoidance precautions

(1) Indoor low floors, turn off the fire source and evacuate to a safe area immediately

(2) If you are on a high floor, turn off the fire source, protect your head, hide in the nearest survival triangle (a small space such as a toilet), seek shelter in the nearest safe place, lie down, cover yourself, and hold on tightly . Do not take the elevator

(3) When taking shelter, stay away from hanging objects, tall buildings, chimneys, parapets, high-voltage wires, etc.

(4) Stay away from mirrors, glass, lighting equipment, etc. when taking shelter