Today, Shichao plans to talk to our colleagues about earthquake early warning. The reason is not because of any technological breakthroughs in our country, but because of new developments abroad. But I guarantee that after reading this article, you will definitely sigh:"Foreigners are really living in dire straits~"Well, not long ago, Google published an article in the American "Science" magazine, saying that they used more than 2 billion mobile phones around the world to form an earthquake early warning network.
And it has been trial run for four years starting in 2021, and the results prove that this technology is effective——The article mentioned that this technology has captured approximately 11,000 earthquakes in the past, and its performance is comparable to standard seismometers.
No, Google, are you finally awake?
In fact, also in 2021, our domestic Chengdu High-tech Disaster Reduction Institute (hereinafter referred to as the Disaster Reduction Institute) reached a cooperation with Xiaomi and launched a similar earthquake early warning function on Xiaomi mobile phones. It also uses the built-in sensors of the mobile phones to detect seismic waves.
It's just that at that time, Xiaomi and the Institute of Disaster Reduction did not submit relevant technical research to serious academic journals such as "Science" like Google.
And for China, we really don’t need to rely on mobile phone earthquake early warning, because it is just a supplementary solution. If we want to be more reliable, we have to rely on our official earthquake monitoring equipment and early warning network.
Therefore, our country actually already has a plan of "mainly traditional earthquake early warning network and supplemented by mobile phone earthquake early warning".
But when it comes to foreign countries, the situation is completely different.
The earthquake early warning systems in many countries either do not exist or are relatively backward. Therefore, for ordinary people abroad,Google's plan is equivalent to a "life-saving straw."
So here I think all friends would like to ask: Whether it is the cooperation between Xiaomi and the Disaster Reduction Institute, or Google's technology, is it really reliable to use mobile phones to detect earthquakes?
Before explaining this, we have to review how the traditional earthquake early warning system works.
Simply put, the core logic of earthquake early warning is to use the "time difference" in the propagation of seismic waves.
Seismic waves are divided into P waves (longitudinal waves) and S waves (transverse waves): P waves propagate fast, have weak vibrations, and are less destructive, while S waves have slow speeds but strong vibrations, and are more destructive to ground buildings.
The traditional earthquake early warning system will detect P waves through seismometers near the earthquake source, use P wave data and mathematical models to estimate the arrival time of the S waves and the intensity of the earthquake, and then the earthquake agency will issue early warning information to the public.
So generally speaking,In order to ensure the accuracy and reliability of the early monitoring stage, the equipment accuracy requirements of the earthquake early warning system will be very high, and seismometers will also be installed on the ground or underground according to different monitoring needs.
The earthquake early warning system developed based on mobile phones is in principle the same as the traditional solution.
It’s just that they used devices to monitor seismic waves,From precision standard seismometers(Strong seismometer), becomes the acceleration sensor on your phone.
As we all know, the acceleration sensor is a component used to monitor the motion status of objects. For example, a mobile phone measures the movement acceleration through the acceleration sensor, and combines it with an algorithm to calculate the number of steps you take every day.
Based on this feature, when the mobile phone is stationary, it will use sensors to detect a sudden increase in acceleration, which is the vibration of seismic waves.
However, the problem here is that compared with standard seismometers, the accuracy of the acceleration sensor is simply not enough, and it is also extremely prone to various false touches.
For example, if you are running in the room, or if a large truck happens to pass by outside, the vibration caused by these situations may be captured by the acceleration sensor on the mobile phone, resulting in misjudgment.
Therefore, how to distinguish earthquakes from regular vibrations in daily life is the key to the mobile phone earthquake early warning system.
The principle is not complicated. Let’s take Google’s earthquake warning system (Android Earthquake Alerts, referred to as AEA) as an example.
When a mobile phone triggers an earthquake warning due to vibration, it will first send acceleration information and approximate location to Google's servers.
After receiving the information, Google will make the first step of judgment, which is to check whether other mobile phones at the same location at the current time have also triggered warnings. Only when there is enough credible trigger information at the earthquake source location, will it declare an earthquake. Then, it will estimate the earthquake time, magnitude, source and other information based on P-wave and S-wave data.
In other words, the Android phone at the epicenter acted as a "whistleblower", while Google combined the information of multiple "whistleblowers" to make a comprehensive judgment.
At this point, everyone should have noticed that Google’s solution actually relies mainly on its huge Android user base. Although the detection quality of seismic waves is not as good as traditional solutions, it is better because it is large enough to allow cross-validation.
So back to the question we asked earlier: How reliable can this be?
According to data released by Google, from April 1, 2021 to March 31, 2024, AEA detected a total of 11,231 earthquakes, 85% of which matched earthquakes listed in the traditional earthquake catalog.
And the accuracy of AEA's magnitude estimation is also improving year by year.
The evolution of AEA’s estimation accuracy for earthquakes above magnitude 4.5
However, Google itself pointed out that of the approximately 1,300 alert events, three were false alarms.
Two of them were due to thunderstorms, and large-scale vibrations caused by thunder caused AEA to generate false alarms.
In another case, a large-scale notification from another alarm system caused mobile phones in a certain area to vibrate collectively, thus triggering the AEA alarm.
During the 7.8-magnitude earthquake in Turkey in 2023, Google's system also underestimated the magnitude (misjudgment as 4.5-4.9) and did not issue warnings to some people until the shaking started. It is difficult for people to fully believe in the stability of this system.
Image source China Earthquake Network
Of course, Google said that these can be improved by optimizing software algorithms.
And Google also said,This AEA warning system is a supplementary service and is not intended to replace the official earthquake warning system.
But then again, even this "supplementary" service provided by Google can be regarded as a national earthquake early warning system for most countries.
Because not all countries located in earthquake zones have the ability and willingness to build a complete earthquake early warning system.
Shichao searched and found that there are probably more than 100 countries and regions in the world located in earthquake zones. However, apart from China, the only countries that have built complete earthquake early warning systems are Japan, Mexico, Romania, Turkey, Italy, and France.
Mexico Earthquake Warning System
Among them, Turkey and Romania have regional early warning systems, which only provide early warning for certain areas with frequent earthquake activity. There are also earthquake early warning systems like France's for high-speed railways along the Mediterranean, which is equivalent to a measure to protect important transportation lines.
The United States, where Google is based, has proposed a plan to build a nationwide earthquake early warning system and has multiple technical solutions. However, it has only implemented a complete earthquake early warning system (USGS ShakeAlert system) on the west coast of the United States.
Dark green is the ShakeAlert system deployed on the West Coast, light green is the Android earthquake warning system
So what Google has done is indeed a good thing for foreigners.
But for China, we look at it more from a melon perspective. After all, whether it is mobile phone earthquake early warning or traditional earthquake early warning, we already have ready-made plans in China.
For example, last year the Earthquake Administration announced that 15,899 observation stations have been built in China, making it the largest earthquake early warning network in the world.
There is also the Disaster Mitigation Institute, which I have told you many times. Their independently developed ICL earthquake early warning system is far ahead in the world.
This system consists of a fully automatic early warning network. Intensive earthquake early warning monitors have been set up in major earthquake areas in the country. After an earthquake occurs, it can issue warnings to users in areas where the seismic waves have not yet reached, from seconds to tens of seconds in advance.
More importantly, the Disaster Mitigation Institute now cooperates with domestic mobile phone manufacturers such as Huami OV. Each mobile phone system has integrated earthquake early warning functions at the bottom level and can be received.
Therefore, missionaries using domestically produced mobile phones can receive earthquake early warning information from the Disaster Reduction Center without operating or spending money.
Earthquake warning service statement for vivo mobile phones
OK, that’s about it for us to talk about the situation of earthquake early warning systems at home and abroad.
Finally, I would like to say that whether it is Google’s AEA Android earthquake alarm abroad or the system-level cooperation between domestic mobile phones and disaster reduction institutes, they are all examples of manufacturers taking on social responsibilities.
However, to deal with such natural disasters, it is obviously not enough to rely on the strength of manufacturers alone. Ultimately, we must rely on the national earthquake early warning project. Fortunately, our domestic efforts in this area are indeed reassuring.