Experts explain in detail the earthquakes in Yangbi, Yunnan and Maduo, Qinghai:

Different fault zones, no correlation analysis

  According to the China Earthquake Networks Center, a magnitude 6.4 earthquake occurred in Yangbi County (25.67 degrees north latitude, 99.87 degrees east longitude) in Dali Prefecture, Yunnan Province at 21:48 on May 21, 2021, with a focal depth of 8 kilometers.

At 2:4 on May 22, a magnitude 7.4 earthquake occurred in Maduo County (34.59 degrees north latitude, 98.34 degrees east longitude) in Guoluo Prefecture, Qinghai Province, with a focal depth of 17 kilometers.

  What are the causes of the two earthquakes and what are the connections?

Monitoring shows that there have been many aftershocks within one day after the earthquakes in the two places. Will there be new major aftershocks?

Experts from the China Seismological Network Center and other departments pointed out after consultation that the two earthquakes are located in different fault zones in my country, and the specific causes and types of earthquakes are different. The Yunnan Yangbi earthquake is a foreshock-mainshock-aftershock type, and the Qinghai Maduo M7.4 earthquake is The main shock-aftershock type only occurred in a similar time. Therefore, no correlation analysis is made.

All are in areas with strong tectonic movement, but occur relatively independently

  The Yunnan area is located on the southeastern edge of the Qinghai-Tibet Plateau, and the Qinghai area is located in the northeast of the Qinghai-Tibet Plateau. Since records, the tectonic movement in the two areas has been strong.

According to the China Seismological Network Center, mainland China is affected by two major plate movements. One is the effect of the Pacific plate from the east on the downward subduction of the Eurasian plate, and the other is from the northward collision of the Indian plate from the south. extrusion.

Under the action of these two large power sources, mainland China, especially on the Qinghai-Tibet Plateau and its surrounding areas, has formed a situation of frequent strong earthquakes.

  According to expert analysis, under the above-mentioned background, the current two earthquakes are still relatively independent.

Xu Xiwei, director and researcher of the National Institute of Natural Disaster Prevention and Control of the Ministry of Emergency Management, pointed out that the Qinghai Maduo earthquake occurred on an active fault inside the Bayan Har block, and the main body of the block moved eastward; while the Yunnan Yangbi earthquake occurred in Sichuan Dian block In the western part of Yunnan, the block where it is located basically moves southward, "it can be said that there is no relationship between the two earthquakes."

  After the China Earthquake Networks Center organized experts to study and judge the Yangbi earthquake in Yunnan, they believed that the earthquake has now constituted a pre-main-subsequent earthquake sequence type.

The site is located in northwestern Yunnan. The nearest fault is the Weixi-Qiaohou fault. The larger fault zone, the Honghe fault zone, also exists here. This structural background is also prone to earthquakes.

  Unlike the Yangbi earthquake in Yunnan, the magnitude 7.4 earthquake in Maduo County, Qinghai is the result of the continuous activity of the Bayan Har block boundary fault.

The nearest fault to Maduo County is the Gande South Margin Fault, which is located in the northern part of the Bayan Har block. The focal mechanism is a strike-slip fracture.

  The reporter learned that the Bayan Har block is located in the northern part of the main part of the Qinghai-Tibet Plateau and is one of the pivotal areas for the direction of crustal movement on the Qinghai-Tibet Plateau.

In the northeastern edge of the Qinghai-Tibet Plateau to the north of the block, there is a strong extrusion and uplifting, and the area to the south of the block is mainly manifested as eastward extrusion.

Under the strong action of this kind of crustal deformation, the activities of the fault zone around the Bayan Har block are particularly intense, and strong earthquakes are frequent.

  Statistics show that since the 1997 Mani earthquake with a magnitude of 7.5, strong earthquakes of magnitude 7 or above have occurred on the marginal faults of the Bayan Har block, including not only the 2001 earthquake of magnitude 8.1 in the west of the Kunlun Mountain Pass that occurred on the main fault. And the 2008 Wenchuan magnitude 8.0 earthquake, including the 2017 Jiuzhaigou magnitude 7.0 earthquake that occurred on the compression and strike-slip deformation zone in the northeast corner of Bayan Har.

The occurrence of the Mado 7.4 earthquake shows that the Bayan Har block is still the main activity area for strong earthquakes in mainland China.

There is still a possibility of a magnitude 5~6 earthquake in the Yangbiyuan earthquake area in recent days

  After the successive earthquakes in Yunnan and Qinghai, some netizens asked, "Are there more earthquakes in my country this year?" In fact, according to the relevant statistics of the my country Earthquake Administration, there are an average of 24 earthquakes of magnitude 5 or higher in mainland China each year, and 4 earthquakes of magnitude 6 or higher. , 0.6 earthquakes with magnitude 7 or above.

The frequent occurrence and wide distribution of earthquakes are the typical laws of seismic activity in my country's mainland.

  After the Yangbi earthquake in Yunnan, aftershocks were relatively abundant. Liu Jie, a researcher at the China Earthquake Networks Center, said that the reason is that the fault zones in this place are intertwined, resulting in strong aftershock activity. This situation is not uncommon. About 10% to 40% of earthquakes.

In addition, monitoring shows that since May 18, 2021, earthquakes of magnitude 4 have been active in the vicinity of Yangbi, Yunnan, and seismic activity levels have rapidly escalated, followed by magnitude 5.6 and 21:48 on May 21 at 21:21 and 21:48. After a magnitude 6.4 earthquake, there have been many aftershocks of magnitude 4 and 5, and the aftershocks of the earthquake sequence are relatively abundant, which are also in line with the seismic characteristics of the pre-main-surgical type.

  At present, the earthquake sequence is still active, and strong sensible earthquakes may occur in the future.

Experts from the China Seismic Network Center pointed out that at present, based on comprehensive analysis of regional tectonic characteristics, historical seismic activity levels, sequence characteristics, and geophysical observations, it is believed that it is unlikely that earthquakes of magnitude 7 or higher will occur in the original seismic area in recent days, but they do exist. The possibility of an earthquake of magnitude 5-6.

  Unlike this Yunnan earthquake, the Qinghai Maduo earthquake showed a typical mainshock-aftershock type.

Statistics show that within 300 kilometers of the epicenter of the Maduo M7.4 earthquake, there have been 5 earthquakes of magnitude 7 or higher since 1900, all of which are major-to-surgical earthquake sequences.

Experts from the China Earthquake Networks Center believe that based on comprehensive analysis of regional tectonic characteristics, historical seismic activity levels, sequence characteristics, and geophysical observations, it is unlikely that an earthquake of magnitude 7 or more will occur in the original seismic area here, and it will not affect Xining and Haidong. , Hainan, Huangnan and other regions have a big impact on work or life.

More emergency earthquake information service products will be put into use

  The reporter learned that when the earthquake occurred in Yangbi County, Yunnan Province on the evening of May 21, many local residents quickly received early warning information on TV or earthquake early warning apps. Later, earthquake early information such as magnitude and source of earthquakes was sent from Weibo, WeChat, and mobile phone text messages. , News client and other channels to provide quick services for local public emergency response.

So, what technologies are used in it?

  The reporter learned that the earthquake information broadcasting robot system started in 2015. It was independently developed by the China Earthquake Network Center and operated fully automatically. It is the "brain" for the production of public service content for earthquake information.

After an earthquake occurs, the system automatically determines and broadcasts it independently. At the same time, it forms a related earthquake report after rapid calculation. Through various information release ports, the earthquake and earthquake information can cover hundreds of millions of netizens within one minute.

"A magnitude 6.4 earthquake occurred in Yangbi County, Dali Prefecture, Yunnan" was automatically generated by an earthquake information broadcasting robot at 21:56:39 on May 21, 2021, and took 15 seconds. Its high-speed, accurate, and professional features won unanimous praise from netizens. .

In addition, the "Earthquake Early Warning" app developed by Chengdu High-tech Disaster Reduction Research Institute also played a role in this earthquake early warning.

  According to the China Earthquake Administration, the construction of the "National Earthquake Intensity Quick Report and Early Warning Project" was launched in 2018. It is planned to use about 5 years to form earthquake early warning in key areas such as North China, the North-South Seismic Belt, the Southeast Coast, the middle section of Tianshan Mountains in Xinjiang, and Lhasa, Tibet. Information service capabilities.

In accordance with the principle of “building while serving”, Sichuan, Yunnan, Hebei, etc., as the “first test” provinces for engineering construction, the whole chain of earthquake early warning systems for earthquake monitoring, data processing, information release, and information reception has been opened up. Sichuan and other regions It has begun to provide earthquake early warning information services on a trial basis.

  In addition, according to the Sichuan Earthquake Administration, the province's seismic intensity quick report and early warning project will soon be put into trial operation in June this year.

The project will build a high-density seismic observation network with an average distance of about 14 kilometers between stations. It will provide earthquake early warning and intensity quick report information services to the whole province in multiple ways and channels, and comprehensively improve the earthquake emergency information service capabilities. Realize the second-level earthquake early warning and minute-level earthquake intensity quick report.

  Experts pointed out that it can be expected that a wealth of emergency earthquake information service products will play an increasingly important role in reducing earthquake disasters, ensuring earthquake safety, and serving social development.

  (Our reporter Yang Shu Zhang Yaxiong)

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