Earthquake Research in China  2019, Vol. 33 Issue (4): 605-616     DOI: 10.19743/j.cnki.0891-4176.201904005
Construction and Development of China's Earthquake Information Release System
JI Yunda, YANG Chen, HUANG Zhibin, ZHAI Luyuan     
China Earthquake Networks Center, Beijing 100045, China
Abstract: Focused on the current situation, monitoring system, technical management regulation, process, system composition, and information publication of the earthquake information release, we summarized the construction and development of China's earthquake information release system and expected its future. In general, China's earthquake information release systems is able to publish auto-results with MS ≥ 3.0 from 1 to 3 minutes, MS ≥ 6.0 in global from 2 to 30 minutes, and formal results with MS ≥ 3.0 in China from 8 to 30 minutes, MS ≥ 6.0 in global from 20 to 60 minutes. These earthquake information is released by various channels such as short message, website, microblog, mobile application, etc.
Key words: Earthquake information release     Technology management regulations     Process of information release     System structure     Information release methods    

INTRODUCTION

Through the construction of the "Chinese Digital Seismic Monitoring Networks", a part of "the Tenth Five-year Plan", China's earthquake monitoring system has fully completed the transition from analog recording to digital recording, and has built a digital seismic observation system consisting of the National Digital Seismic Network, 31 regional digital seismic networks, 6 volcanic earthquake networks, 2 arrays and mobile seismic networks, which indicates that earthquake observation in China has entered into the digital era. As an important part of earthquake monitoring, earthquake information release has a long history. From the large earthquake information release in the analog era to the practical application of automatic information release in the digital era, the ability, coverage area and speed of earthquake information release have been improved continuously. By introducing the current situation, monitoring system, technical management regulations, process, and system composition of earthquake information release as well as the publication of earthquake information, the paper summarizes the construction and development of earthquake information release system in China, and gives the prospect of further earthquake information release.

1 CURRENT SITUATION OF EARTHQUAKE INFORMATION RELEASE

At present, the task for rapid earthquake information release in China is jointly completed by China Earthquake Networks Center and provincial earthquake networks centers. They are responsible for quick information release of MS≥3.0 earthquakes in the Chinese mainland, MS≥4.0 earthquakes in Taiwan, China, MS≥6.0 earthquakes in the global continent and MS≥7.0 earthquakes in the global marine area. Table 1 illustrates the results from earthquake information release in China from 2015 to 2018, while Fig. 1 and Fig. 2 show the epicenters detected by earthquake information release from 2015 to 2018 in China and worldwide, respectively. (A Formal Catalogue of China's Earthquake Information Release, 2018).

Table 1 Situation of China's earthquake information release

Fig. 1 Epicenters detected by earthquake information release in China

Fig. 2 Epicenters detected by earthquake information release around the world

Table 2 Error and time of auto and manual earthquake information release

Compared with the formal catalogue(The United National Cataloging System, 2019), for domestic earthquakes, the epicenter error is 11.775km and magnitude error is 0.35 in Auto-information-release which takes 159.25s, while the corresponding errors are 4.6km and 0.21 in Manual-information-release which takes 667.75s; for overseas earthquakes, the epicenter error is 14.43km and magnitude error is 0.31 in Auto-information-release which takes 816.75s, while the corresponding errors are 7.25km and 0.22 in Manual-information release which take 2113.5s.

2 EARTHQUAKE MONITORING SYSTEM 2.1 Distribution of Seismic Stations Nationwide

Currently, there are 1107 fixed seismic stations in operation nationwide, including 166 national stations, 881 regional stations, 33 volcano stations and 27 stations in 3 arrays, and the distribution of nationwide seismic stations is shown in Fig. 3.

Fig. 3 Seismic stations distribution in the Chinese mainland
2.2 Integral Structure of Earthquake Monitoring System

In addition to fixed seismic stations, the national seismic monitoring system also includes mobile stations, foreign aid stations and global GSN stations. The integral structure of the system is shown in Fig. 4.

Fig. 4 Structure of China's earthquake monitor system

The national seismic stations and regional seismic stations are collected to the provincial seismic networks center, and mobile stations are collected to the provincial seismic network center through the mobile seismic networks. The provincial seismic networks center will exchange all stations in the province with China Earthquake Networks Center through industry network. Meanwhile, the global GSN stations are collected to China Earthquake Networks Center through the internet, while the foreign aid stations are collected to China Earthquake Networks Center via both the internet and satellite channels. Data from all stations are collected and forwarded through the streaming server in real time.

3 REGULATIONS ON TECHNOLOGY MANAGEMENT OF EARTHQUAKE INFORMATION RELEASE

In order to improve the quality of earthquake information release and strengthen the management of earthquake information and parameter release, the Department of Earthquake Monitoring and Prediction, China Earthquake Administration issued The Regulations on Technology Management of Earthquake Information Release(Department of Earthquake Monitoring and Prediction, China Earthquake Administration, 2015) and The Regulations on Technology Management of Automatic Earthquake Information Release (Department of Earthquake Monitoring and Prediction, China Earthquake Administration, 2013). These two regulations standardized both earthquake information release and automatic earthquake information release, which are the basis and guidance of earthquake information release.

3.1 Regulations on Technology Management of Earthquake Information Release

The Regulations on Technology Management of Earthquake Information Release(2015 Revision) is formerly known as The Regulations on Earthquake Information Release and Earthquake Parameter Release. The first edition was officially implemented on September 1, 2008, and after more than four years of operation, the revised edition of the regulation was issued on March 22, 2013 and then formally implemented on April 1, 2013. In order to guarantee the quality of earthquake information release and to regulate the publication of earthquake information release and earthquake parameter, these rules are revised and formulated on the basis of The Regulations on Technology Management of Earthquake Information Release (2013 Revision). The regulations are mainly divided into the following parts: basic parameters of earthquake information release referenced geographical names for epicenters, information release tasks and time requirements of China Earthquake Networks Center and provincial earthquake networks center, the determination of parameters from earthquake information release, report, publication, and update of earthquake information release parameters.

According to the regulation, the official earthquake information release of China Earthquake Networks Center should follow the "3-7 rule", that is, official information release for MS≥3.0 earthquakes in the Capital area(10 minutes), MS≥3.0 earthquakes in Yangtze River Delta, the Pearl River Delta, Chongqing and provincial capitals(15 minutes), MS≥4.0 earthquakes in eastern areas of China within 50km offshore(20 minutes), MS≥5.0 earthquakes in other regions of China(30 minutes), MS≥6.0 earthquakes in border areas(40 minutes), MS≥6.0 earthquakes in continental areas around the word and MS≥7.0 earthquakes in the global sea areas(60 minutes). Meanwhile, earthquake information release of Provincial Earthquake Agencies should follow the "3-6 rule", that is, MS≥3.0 earthquakes within 50km outside the boundary of the administrative region(administrative region is included), MS≥4.0 earthquakes within 100km (the administrative region is not included), MS≥5.0 earthquakes within 200km (the administrative region is not included), MS≥6.0 earthquakes within 300km (the administrative region is not included) and big- and medium-sized cities within the administrative region.

In addition to the task and requirements of information release, the regulation also makes clear provisions on the report and release of earthquake information. For the released earthquake information, the magnitude M is used(Xu Shaoxie et. al., 2004) and each earthquake can only use the results from the national network(including the fast report results and final forwarded report from the national network) as the unique official results.

3.2 Regulations on Technology Management of Automatic Earthquake Information Release

In order to further improve the ability of automatic earthquake information release in China and achieve the goal named "Improving the timeliness and accuracy of automatic information release and promoting the establishment of the direct train of automatic information release service", China Earthquake Administration revised The Regulations on Technology Management of Earthquake Information Release issued in 2009 by the development and deployment of the integrated trigger platform and improvement and upgrade of the automatic earthquake information release system. The revised edition came into effect on April 1, 2013 and the regulations are mainly divided into the following aspects: system composition, tasks and responsibilities, automatic information release parameter output, information release and update, operating maintenance, and condition guarantee.

According to the regulation, China Earthquake Networks Center outputs the automatic information release parameters of earthquakes with MS≥2.5 in China and MS≥5.5 earthquakes in global area and produces the comprehensive trigger results of domestic MS≥3.0 earthquakes (including MS≥4.0 earthquakes in Qinghai, Xinjiang, Inner Mongolia, Tibet and Taiwan) and MS≥6.0 earthquakes in foreign countries (AU). The Backup System of the National Earthquake Information Release outputs automatic information release parameters of domestic MS≥2.5 earthquakes as well as MS≥5.5 earthquakes in foreign countries and uploads them to China Earthquake Networks Center.

In addition to the tasks and requirements for automatic earthquake information release, the regulations also make clear provisions on the publication and update of automatic earthquake information release. Only the comprehensive trigger ones (AU) from automatic earthquake information release results can be published, while other results are only for internal reference and are not allowed to be published outside the system. China Earthquake Networks Center and provincial earthquake networks center are supposed to verify the comprehensive trigger results within the scope of their information release, correct them if the results are falsely triggered, and update them with manual earthquake information release results if the results are confirmed as earthquake events.

4 PROCESS OF EARTHQUAKE INFORMATION RELEASE AND SYSTEM COMPOSITION 4.1 Process of Earthquake Information Release

According to The Regulations on Technology Management of Earthquake Information Release and The Regulations on Technology Management of Automatic Earthquake Information Release, the current process of earthquake information release in China is shown in Fig. 5, and the process of global earthquake information release is shown in Fig. 6.

Fig. 5 Process of China earthquake information release

Fig. 6 Process of global earthquake information release

For domestic earthquakes, within 1-3 minutes after an earthquake, the automatic positioning results and comprehensive trigger results from the networks center, backup center and regional center are sent to the core personals of the earthquake administration for reference. Within 3-15 minutes, the interaction results from provincial earthquake networks are reported to China Earthquake Networks Center as the initial report. Within 8-30 minutes, the interaction results from China Earthquake Networks Center are reported to the China Earthquake Administration as an official report and then fed back to provincial earthquake networks. After the report is completed, the official report will be reported to the State Council of P.R.C., and released to the news media and the public.

For earthquakes around the world, within 2-30 minutes after an earthquake occurred, the automatic positioning results and comprehensive trigger results from the networks center and backup center are sent to the core personnel of earthquake administration for reference. Within 10-30 minutes, the interaction results from China Earthquake Networks Center and global seismic networks are sent to the personnel on duty as the initial positioning results. Within 20-60 minutes, the interaction results from China Earthquake Networks Center are reported to China Earthquake Administration and fed back to provincial earthquake networks. After the report is completed, the official report will be reported to the State Council of P.R.C., and released to the news media and the public.

4.2 Automatic Earthquake Information Release System

The National automatic earthquake information release system is composed of automatic information release output system, integrated trigger system, data exchange system and parameter release system (Yang Chen et al., 2014). The overall structure of the national automatic earthquake information release system is shown in Fig. 7.

Fig. 7 Structure of auto earthquake information release system

The result output system of automatic information release is composed of several organizations, which include the output of automatic earthquake information release processing systems of China Earthquake Networks Center, The Backup System for the National Earthquake Information Release(Guangdong Earthquake Agency) and regional automatic earthquake information release center(Earthquake Agency of Hebei, Liaoning, Fujian, Shanxi and Yunnan). The above organizations respectively send the automatic information release results of their own output to the automatic EQIM root server in China Earthquake Networks Center through the EQIM server deployed in the corresponding organizations.

The comprehensive trigger system collects the automatic information release results from network centers, backup centers and regional centers, outputs the comprehensive trigger results based on the strategy called "multi-channel comprehensive triggering"(code AU: Auto Location), and forwards the results to the automatic EQIM root server through the EQIM server.

The data exchange system consists of automatic EQIM systems of China Earthquake Networks Center and provincial earthquake network centers. All automatic earthquake information release results are collected and forwarded through the automatic EQIM root server of China Earthquake Networks Center, and provincial earthquake network centers receive all the automatic earthquake information release results through the local automatic EQIM server.

The parameter release system only receives the comprehensive trigger results from the automatic earthquake information release, as the data source that is published by the automatic trigger source. The comprehensive trigger results are provided to the duty room, emergency, forecast and other departments of the administration. Furthermore, through the automatic EQIM publish server, messages are sent to internal staffs of the system through the 12322 system, and meanwhile, are published through multiple channels such as webpages, microblogs and mobile applications.

4.3 Manual Earthquake Information Release System

Based on the EQIM system, the national manual earthquake information release system is composed of the exchange system of the national earthquake information release and the release system of official earthquake information report. The overall structure of the national earthquake information release system is shown in Fig. 8 (Yang Chen et al., 2009).

Fig. 8 Structure of earthquake information release system

The data exchange system of the national earthquake information release consists of China Earthquake Networks Center and provincial earthquake networks centers. Earthquake information release results from provincial earthquake networks center are output by manual information release system and sent to the local EQIM server. Then, the information is sent to the EQIM root server of China Earthquake Networks Center through the EQIM server of each provincial earthquake network, and the results fed back by China Earthquake Networks Center are received by the server. China Earthquake Networks Center receives manual results, which are sent by provincial networksthrough EQIM root server, and feeds back by forwarding initial report (CA) and final report (CD). Meanwhile, the official information release results (CC) from China Earthquake Networks Center are also exchanged through the EQIM root server.

The publishing system of the official earthquake information release only accepts earthquake information release results confirmed by China Earthquake Networks Center (CC, CA, CD), as the data source that is published by the earthquake information report. The confirmed earthquake information release results are provided to the duty room, emergency, forecast and other departments of the administration. Furthermore, through the EQIM publish server, messages are sent to internal staffs of the system through the 12322 system, and meanwhile, are published through multiple channels such as webpages, microblogs and mobile.

5 PUBLISHMENT OF THE EARTHQUAKE INFORMATION RELEASE RESULTS

Based on The Regulations on Technology Management of Earthquake Information Release and The Regulations on Technology Management of Automatic Earthquake Information Release and on the premise of "Unified Release with different contents for Internal and External", the publishment of earthquake information release results is mainly classified as internal release and public release according to the classification of the release results. The contents and ways of the two kinds of publishment are different, which are described below, respectively.

5.1 The Internal Release of Earthquake Information Release Results

For the internal of the earthquake monitoring system, all the initial information from earthquake information release is published content. Among them, the manual earthquake information release results incorporates the original earthquake information release results from provincial networks, the initial forwarded report, the final forwarded report and the official earthquake information release results of China Earthquake Networks Center, while the automatic earthquake information release results incorporates the original automatic information release results from network center, backup center and regional center and the comprehensive trigger results. For other departments of the earthquake system, the publishment of manual earthquake information release results do not include the original earthquake information release results from provincial networks, but only includes the initial forwarded report, the final forwarded report and the official earthquake information release results of China Earthquake Networks Center, while the automatic earthquake information release results do not include the original results from their respective automatic information release center, but only includes the comprehensive trigger results. For the entire earthquake system(both the internal and external of the earthquake monitoring system), earthquake information release results are mainly published by mobile phone short messages, websites, microblogs, mobile phone applications, etc.

5.2 The Public Release of Earthquake Information Release Results

For the external of the earthquake system, only the comprehensive trigger results of automatic information release and the official results of manual information release (including the final report forwarded and the official information release of China Earthquake Networks Center) can be published. Among them, the automatic information release results must be confirmed by manual information release results. The earthquake information release results are mainly published by websites, microblogs, mobile phone applications, etc.

5.3 An Extension for Earthquake Information Release

After earthquake information release is completed, for MS≥5.0 earthquakes in Chinese mainland, MS≥5.5 earthquakes in Taiwan, China and MS≥7.0 earthquakes in foreign countries, the output procedure of earthquake emergency products will be activated to face large earthquakes. The main products are: the epicenter location of the main shock and basic parameters, the distribution map of historical earthquakes, the distribution map of seismic stations in the seismic zone, ShakeMap, the accurate positioning of aftershocks, focal mechanism solution and the distribution of historical moment tensor GCMT, population heat map, regional seismic structure map and source rupture process. The first-time output occurs within 2 hours after an earthquake and is updated as the data increase.

6 CONCLUSION AND PROSPECT

With the development of earthquake intensity information release and earthquake early warning project in China, more and more seismic stations will be deployed in China. Correspondingly, under the support of a denser earthquake network, the lower limit of the ability of earthquake information release and the timeliness of information release will be further improved. In addition, with the more extensive application of the automatic earthquake information release technology and the deeper understanding of this technology by the public, the earthquake early warning will gradually come into our view and the earthquake information release combined with its derivative products will better serve the earthquake disasters mitigation.

ACKNOWLEDGMENT

We want to show our sincere appreciation to all the colleagues at China Earthquake Networks Center and provincial earthquake networks for their help and support.

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