To what extent can an earthquake early warning save lives? The warning time is 20 seconds, which can reduce casualties by 63%.
Author: Chengdu Institute of High-tech Disaster Reduction
1. What should I do if I receive an alert?
Basic principles: do not panic, do not jump off the building, do not take the elevator
Reasonable evacuation measures should be selected according to the early warning time and the time to avoid danger to the nearest safe place
Recommended hedging measures:
You should pay attention when taking a hedge
(1) When driving, slow down and stop, and turn on the emergency lights at the same time
(2) In the lower floors of the room, turn off the fire source and evacuate to a safe place urgently
(3) Indoor high-rise, turn off the fire source, protect your head, take refuge in the nearest life triangle area (toilet and other smaller spaces), take refuge in the nearest safe place, lie on the ground, block, and grasp it firmly. No elevators
(4) When avoiding danger, stay away from hanging objects, high-rise buildings, chimneys, parapet walls, high-voltage lines, etc.
(5) Stay away from mirrors, glass, lighting equipment and other items when avoiding danger
The software system is set manually
1. Phone background settings
Background running permission: keep the software running in the background, turn on boot auto-start and background start;
Network settings: Keep the network connected and turn on unmetered usage at the same time;
Saver/Power Consumption Settings: Regardless of power consumption reminders/unlimited power
Notification settings: Turn on all notification permission management as much as possible, including allow notifications and overlay notifications.
Location Permissions: Turn on the location permissions of the software
When all conditions are met, the mobile phone software can be guaranteed to operate normally, and the earthquake warning can be received in real time when an earthquake occurs.
2. Trigger condition setting
Click "Settings" in the upper right corner of the main interface of the software, and set the warning strategy (magnitude threshold and intensity threshold) during the day and night in the "Warning Policy".
Magnitude and intensity are different concepts, and an earthquake has only one magnitude. Intensity refers to the amount of damage that an earthquake can cause to the user's area, which decreases as the distance from the epicenter increases.
Recommended settings: magnitude threshold level 4, intensity threshold 2.0 (for specific settings, please refer to the following popular science "Introduction to Magnitude and Intensity")
3. Principle of earthquake early warning
By setting up dense (station spacing 15-20 km) earthquake early warning monitors (intensity meters) in the main earthquake areas, when an earthquake occurs, the principle that radio waves are faster than seismic waves is used to alert the target before the destructive seismic waves arrive, so that the people can avoid danger in time to reduce casualties, and emergency treatment of important projects to reduce economic losses and secondary disasters.
Fig.1 Earthquake warning intention
4. Five elements of earthquake early warning
The five elements of earthquake early warning include the time of earthquake, the location of the epicenter, the magnitude and estimated intensity of the early warning, and the early warning time.
Earthquake time: The time when the earthquake occurred
Estimated severity: The amount of damage that the earthquake is likely to cause to the user's area.
Warning time: The time when a destructive seismic wave is about to arrive
During the Wenchuan earthquake, Beichuan can have a warning time of 31 seconds, and Qingchuan can have 55 seconds.
Magnitude: The magnitude of the earthquake itself, which is determined by the energy of the seismic waves emitted by the source, and there is only one magnitude of an earthquake.
Intensity: The impact and damage of an earthquake in your area. The intensity is related to the magnitude of the earthquake, the depth of the hypocenter, and the distance from the epicenter. The intensity decreases with increasing distance from the hypocenter.
5. Magnitude and intensity
Magnitude description
The internationally used magnitude of earthquakes, the Richter scale, was developed by the American seismologists Richter, and it ranges from 1 to 10. It is directly related to the amount of energy (thermal energy and kinetic energy) released from the center of the hypocenter, and the greater the energy released by the source, the greater the magnitude.
Classification of earthquakes by magnitude:
Weak earthquake: an earthquake with a magnitude of less than 3, which is almost imperceptible to humans;
Felt earthquake: Earthquakes with a magnitude equal to or greater than 3 and less than or equal to 4.5 will be felt;
Moderately strong earthquake: an earthquake with a magnitude greater than 4.5 and less than 6, the earthquake will be felt strongly, the house will be damaged, and there will be casualties;
Strong earthquake: An earthquake with a magnitude equal to or greater than 6 (such as the Yushu earthquake). damage to houses, casualties;
Huge earthquakes: Earthquakes with a magnitude greater than or equal to 8 are also called huge earthquakes (such as the Wenchuan earthquake). There was a serious collapse of houses and serious casualties
Intensity description
China divides the intensity table according to 12 intensity levels:
1 degree: non-inductive – only recorded by the instrument
2nd degree: slightly sensible – individual sensitive people feel it in complete stillness
3 degrees: slightly sensible - a small number of people in the room feel it at rest, and the hanging object swings slightly
4 degrees: more sensation - most people indoors, a few people outdoors, hanging objects swing, unstable utensils rattle
5 degrees: Wake up - most people outside feel restless, livestock are restless, doors and windows rattle, cracks appear on the surface of walls
6 degrees: panic - people are unsteady on their feet, domestic animals have fled, utensils have fallen over, rudimentary sheds have been damaged, steep slopes have landslided, walls have cracked, and eaves tiles have fallen
7 degrees: Damage to the house - slight damage to the house, damage to the archway, chimney, cracks and sand spraying on the surface, people in the car feel it
8 degrees: building damage - moderate damage to houses, a few damage to the roadbed collapse, underground pipe rupture, most people have difficulty walking
9 degrees: general destruction of buildings - severe destruction of houses, a few topples, collapse of archways, chimneys, etc., bending of railroad tracks, pedestrians falling
10 degrees: Widespread destruction of buildings – houses topple over, roads destroyed, rocks collapse in large quantities, waves on the water surface hit the shore, people fall off the spot, and there is a sense of throwing
11 degrees: Destruction - a large number of houses have collapsed, large sections of the roadbed embankment have collapsed, and the surface has changed greatly
12 degrees: Mountains and rivers change - all buildings are destroyed, the terrain changes drastically, and animals and plants are destroyed
6. Coverage area
Mexico and Japan are the first and second countries in the world to build earthquake early warning systems, respectively. The mainland is the third country to have an earthquake early warning system.
After the Wenchuan earthquake, Dr. Wang returned to China to form a team to focus on earthquake early warning research. Chengdu High-tech Disaster Reduction Research Institute and city and county earthquake prevention and disaster reduction departments (earthquake departments) have jointly built the world's largest continental earthquake early warning network extending to 31 provinces (municipalities and autonomous regions), covering an area of 2.2 million square kilometers, covering 90% of the population (660 million people) in the mainland earthquake area, accounting for 90% of the first-line areas with dense earthquake early warning population. The mainland earthquake early warning network has continuously warned all destructive earthquakes in the network, such as the Lushan magnitude 7 earthquake, the Ludian magnitude 6.5 earthquake, the Jiuzhaigou magnitude 7 earthquake, and the Yibin magnitude 6 earthquake, without any false alarms or omissions. At the same time, the earthquake early warning technology has served Nepal and achieved interconnection with the earthquake early warning network in Chinese mainland, and began to serve the "Belt and Road" national strategy.
Map of the distribution of the earthquake early warning network in the mainland of the Disaster Mitigation Institute
The red line in the figure is the earthquake fault zone, and the green coverage area is the coverage area of the early warning network built by the application of ICL earthquake early warning technology, covering an area of about 2.2 million square kilometers, covering 660 million people, accounting for 90% of the population of China's earthquake area.
7. The function of earthquake early warning
Earthquake early warning has the following 4 functions:
Escape: The house may be damaged and emergency evacuation is required
Evacuation: Furniture, chandeliers, etc. may tip over and need to be evacuated urgently
Centering: The shaking is slight, and the heart is calm
Notification: Tremors may not be felt, but an earthquake is informed
Source: Chengdu Earthquake Prevention and Disaster Reduction Bureau
8. The significance of earthquake early warning
The study shows (Northwest Seismological Journal, No. 12, 2002) that the casualties can be reduced by 14% when the earthquake warning time is 3 seconds, 39% when the earthquake warning time is 10 seconds, and 63% when the earthquake warning time is 20 seconds.
Without an early warning system, people's response to an earthquake is roughly as follows:
With an early warning system and Xi in peacetime, the response process of the earthquake roughly becomes:
With the early warning system, the early warning time has increased, the judgment and decision-making time has been reduced, and the risk avoidance time has been greatly increased.
Taking the 420 Lushan earthquake as an example, the early warning system provided a 5-second warning time for the main urban area of Ya'an City and a 28-second warning time for Chengdu City
9. Characteristics and shortcomings of earthquake early warning
Earthquake warning is issued within a few seconds when an earthquake is occurring, and its principle leads to insufficient earthquake warning:
(1) Earthquake early warning only has a few seconds to tens of seconds warning time
(2) The warning magnitude will be updated gradually, and there may be deviations from the final magnitude (about 10 minutes after the earthquake).
(3) Earthquake early warning is only one of the means of disaster reduction. It is necessary to popularize science and drill to improve emergency response capabilities
(4) Early warning blind spots
From monitoring to seismic waves, analysis and processing by the early warning center to issuing early warning information, earthquake early warning has a systematic response time and an early warning blind spot.
The seismic shear wave is more destructive, and the shear wave warning blind zone (generally referred to as the warning blind zone) feels strong shaking without receiving the alarm, and the radius of the shear wave warning blind zone of the ICL early warning system is about 21km.
10. Earthquake early warning and earthquake forecasting
Earthquake early warning refers to the use of the speed difference between radio waves and seismic waves to warn the target before the arrival of destructive seismic waves when an earthquake occurs. The earthquake warning only has a few seconds to tens of seconds of early warning time, and users receive early warning to avoid danger and emergency treatment in time. It has been applied in Mexico, Japan, China, Nepal, and the United States.
Earthquake prediction (earthquake forecasting) refers to the results discussed by earthquake prediction experts and administrative leaders in a meeting before an earthquake occurs, and there is time (hours or days) to organize a meeting of experts to discuss and decide whether to release it. Earthquake prediction is still a scientific problem.