August 3, the earthquake struck. As at 8:40 on the 4th, this 6.5 earthquake in Ludian county in Zhaotong City, Yunnan Province Town leading occurring, has caused 381 deaths.
Prior to the earthquake, Zhaotong Seismological Bureau Disaster Mitigation Institute and Chengdu Hi-tech joint construction of earthquake early warning system has been found success early warning and earthquake omen for Kunming Zhaotong city and provide 10 seconds, 57 seconds warning, respectively. This valuable tens of seconds warning, successfully saved many lives.
Over the years, every major earthquake, the Internet Association Japan, earthquake prediction spread "myth", away with the god of dance, all kinds of stories hit the jackpot, the only fly only "earthquake early warning."
What is an earthquake early warning system?
In fact not predict the earthquake early warning, the concept was first proposed in 1868 by the United States Cooper (JDCooper) Ph.D., the basic principle is the P-wave (a kind of longitudinal wave) propagate faster than S waves (s-wave), electromagnetic wave propagation faster than seismic waves, use the time difference between the two early warning. But limited to the technical level, this idea did not materialize.
Until about 100 years later, the Japanese earthquake alarms laid along the railway line, was the first time this idea into reality and applied to earthquake disaster prevention.
The Yunnan earthquake proof, earthquake early warning system construction of China is catching up, and attract more public attention.
As early as February 2013 No. 19, occurred near Zhaotong Qiaojia County 4.9 earthquake. Chengdu Hi-Tech Disaster Mitigation Institute of Zhaotong City, Yunnan Bureau of Earthquake Disaster Mitigation joint construction of earthquake early warning system for the success of earthquake early warning. This is the first time earthquake early warning system for the success of the devastating earthquake early warning. Since then, the Chengdu earthquake early warning system has been warning of the damage caused by an earthquake 14 times.
Earthquake early warning requires enormous base station construction. Through the implementation of the China Seismological Bureau, "15" major projects "Digital Earthquake Observation Network", has built a nationwide earthquake monitoring network consists of a national network of seismic stations and 32 provincial seismic network composed. National Seismic stations reached 1014 (Fig. 2), which includes 148 national stations, regional stations 814, Volcano stations 33, array 2, 19 sets of points.
And Seismic Network evenly distributed in different provinces, China's Strong Motion Network (Fig. 3) are mainly distributed in 21 earthquake surveillance and protection zone, a total of 1154 earthquake fixed stations, in addition to Beijing, Tianjin, Lanzhou , Kunming and Urumqi five cities intensity quick report station network totaled 300 stations intensity quick report, but all of our stations are dialing earthquake upload data, not real-time data transmission function.
Why not earlier warning?
Earthquake early warning of course, the sooner the better, but because of technical limitations, warning technically difficult to achieve the effect of earlier forecasts.
Earthquake early warning takes time, this time includes not only P-wave propagation time to the station, including earthquakes positioning time, computer processing and release time, data transfer delay and system response time. It is because of these times, when the earthquake early warning alerts have been issued, seismic wave propagation has been some distance, then the corresponding S-wave propagation distance, which we call "blind spot." Obviously, for the blind zone areas are unable to provide early warning information.
The main limitations of earthquake early warning system is the presence of blind spot warning. Therefore, the earthquake early warning system faces an awkward rule: the shorter the more intense extreme ground motion earthquake zone, to provide early warning of the the weaker regions dependent on the early warning system, warning time can provide but longer. Wenchuan earthquake as an example: less than 20 kilometers from the epicenter Yingxiu, in the blind spot warning, basically not possible to get advance and about 1,500 km from the epicenter of Beijing, about 3 minutes obtained advance warning, but almost Pointless.
Chinese Academy of Engineering Xu Shaoxie noted unavoidable blind spot warning, only by virtue of technological progress is gradually narrowing.
An earthquake early warning area How to choose?
According earthquake warning way, now divided into earthquake early warning to alert (on-site warning) and remote alarm (regional warning). The former "protected objects" as the goal, in the protected object around "draw" a circle, the circle once detected "trouble" to take immediate measures equivalent to sentries located in their positions the latter "threat "as the goal, to monitor the" threat ", once it appears, to take immediate steps to set up the equivalent of the outpost in enemy strongholds around.
Key protection including nuclear power plants and the like. Guangdong Daya Bay Nuclear Power 1994 earthquake alarm device built by the six accelerometers, four peak accelerometer, two earthquakes flip-flops, the Qinshan Nuclear Power Plant, Lingao Nuclear Power Station also built a similar earthquake alarm device. 2007 Jining High Pressure Gas Transmission Pipeline Construction of China's first oil and gas pipelines seismic alarm system, which is also used in the construction of the China-Burma oil and gas pipelines and the like. For high-speed railway, China's Beijing-Tianjin passenger line, Beijing-Shanghai high-speed railway, Beijing-Guangzhou Passenger Line and along the Ha - Da passenger line had been laid or intended to be laid seismic monitoring system.
Obviously, remote warning with respect to the current warning, disaster prevention and better overall results, but we often can not accurately predict where earthquakes occur, and the object to be protected can not completely avoid all faults. Due to the high cost of construction and maintenance of earthquake early warning system that only has a certain value and to protect the earthquake have a certain frequency region have warning system construction significance.
Overall, taking into account the off-site warning situation, we can develop appropriate standards for seismic hazard and population, economic and lifeline engineering, etc., only when all the indicators are an area exceeds the standard threshold, currently only it is necessary to deploy an earthquake early warning system.
Focus on how to divide the warning area?
With respect to the earthquake early warning system has been fully deployed in China, Japan and Taiwan, mainland China's land area much larger than they are, the frequency of the earthquake relatively low per capita economic strength, there is a certain gap. Clearly, the current full deployment of earthquake early warning system in the country is not a good way to draw the focus was more practical and effective early warning area.
At present, China by some basic parameters to determine a preliminary analysis of earthquake early warning select key areas.
Since 1970, in addition to the metropolitan area, and several strong earthquakes in Liaoning Province, the major earthquake in mainland China are concentrated in Heihe - Tengchong line near the west (population geographical boundaries) or the near Urumqi in western population is more concentrated some earthquake, but the frequency and intensity are to be located below the Heihe - Tengchong line of Sichuan-Yunnan region. On this basis, it can be initially identified four key areas for the region of earthquake early warning (block of Figure 5): the northwest region of Xinjiang, Sichuan-Yunnan region, the Capital Region and the southeastern coast.
The key problem of earthquake early warning system architecture design
Existing seismic monitoring system is similar in framework of existing early warning to early warning and remote, earthquake early warning system mainly consists of observing systems, communication systems, handling systems, distribution system and security system, each of the different sub-systems and system configuration, the overall architecture is shown in Figure 7.
On a similar structure, due to the special timeliness earthquake early warning, the key issue of its architectural design and seismic monitoring system not exactly the same. As a whole, observation and communications systems belonging infrastructure is fundamental to the whole system is running.
Now with respect to the monitoring system, it is not particularly important publishing systems and security systems have become critical earthquake early warning system architecture design: determines the effectiveness of the entire distribution system of early warning systems, and the security system is the whole system running smoothly the most critical part. Existing earthquake monitoring systems major earthquake quick report published information, including information and automatic earthquake bulletin artificial earthquake breaking news information.
The Zhaotong earthquake, highlights the importance of the publishing system. Chengdu Hi-tech mitigation director Wang Tun said in Zhaotong City, the local intensity degrees, the maximum seismic intensity of extreme earthquake zone. "When the earthquake occurred on a weekend, most people have at home, the local general Zhaotong four or five floors in height or less. If people can receive earthquake early warning, ran into the bathroom you can in 10 seconds, the lower floors were also you can go outside the building to avoid casualties. "
But one earthquake science department is not enough, on the other hand the government led to inadequate publicity, earthquake early warning failed to maximize performance. "Earthquake early warning should be formed through television, mobile phones and other terminal-dimensional network, the earthquake early warning made everyone a means to protect life safety."
May 14, 2012, Chengdu Hi-Tech Disaster Mitigation Institute had warned attempt by television. 12:00 the same day, Qingchuan occurred 1.3 earthquake. Article 9 seconds warning information in the form of subtitles on the television release after the earthquake: "Tips, being a minor earthquake in Qingchuan, Wenchuan County Wenchuan Earthquake Disaster Mitigation Board felt free, Chengdu Hi-tech Mitigation Institute." While TV channels still essential, but in the new media age, in just two years, this early attempt has become somewhat outdated.
For most of the domestic earthquake quick report Published information automatically about 1 to 2 minutes, the artificial breaking news Published information is 5 to 15 minutes, publish main methods of website, SMS, microblogging and mobile client. Earthquake early warning system requires higher timeliness in the process of challenging the limits of time, the traditional publishing methods can not fully meet their needs.
After the earthquake, we believe will accelerate the construction of earthquake early warning distribution channel micro-channel, microblogging, TV, and a race against time, and earthquake contest has only just begun.
(Author: Andy Zhang, IT, media herein by reference paper "several key issues China Earthquake Warning System," by Yang Chen)
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