Why do earthquakes occur frequently in Sichuan?

Yesterday, a magnitude 6.8 earthquake occurred in Luding County, Ganzi Prefecture, Sichuan Province (29.59 degrees north latitude, 102.08 degrees east longitude), with a focal depth of 16 kilometers.

This is already a very high-level earthquake, and many places have felt it. This earthquake is very close to a major earthquake (magnitude 7), and this is just a microcosm of the Sichuan earthquake. Why do earthquakes occur frequently in Sichuan? Let's talk about it today!

01. Why do earthquakes occur frequently in Sichuan?

In fact, Sichuan can be said to be a place in my country where major earthquakes frequently occur, mainly due to the geological problems here.

This earthquake occurred in the Xianshuihe Fault Zone. Many people may be more familiar with the Longmenshan Fault Zone, where the Wenchuan earthquake occurred. Together with the Anninghe Fault Zone, these are the three most active and dangerous fault zones in Sichuan, where large earthquakes frequently occur.

Xianshui River is a tributary of Yalong River, located in Ganzi Tibetan Autonomous Prefecture in western Sichuan, and was called Xianshui and Zhoujiang in ancient times. However, this area is also the northeastern boundary fault where the material of the Qinghai-Tibet Plateau is squeezed eastward and southward, so it has become one of the most active fault systems in inland my country.

Since 1700, this fault zone has experienced 17 earthquakes of magnitude 7 or above and 29 earthquakes of magnitude 6.5 or above. In the Xianshuihe fault zone alone, there have been 9 earthquakes of magnitude 7 or above in the past 300 years, with an average of one major earthquake every 36 years.

The last major earthquake was probably the 7.6 magnitude earthquake in 1973.

02. About this earthquake

After the 8.0 Wenchuan earthquake and the 7.0 Lushan earthquake in 2013, Xianshuihe was in a high-risk period. Studies have found that the local Coulomb stress has increased significantly, and the strike-slip rate of the Xianshuihe fault zone has increased from northwest to southeast.

Seismologists believe that there is a high possibility of a major earthquake in the area.

However, we are currently unable to predict earthquakes. We only know that the possibility of earthquakes in this area is increasing, but we cannot predict the exact time.

Therefore, we can only strengthen protection. For example, on the one hand, we should carry out emergency drills, and on the other hand, we should improve the earthquake resistance of the buildings in the area.

Finally, how much energy was released by this earthquake? Is this energy enough? More research is needed.

When faced with natural disasters such as earthquakes, we can only take precautions and make preparations.

This also reflects that because Sichuan is located on the edge of the Qinghai-Tibet Plateau, the first of my country's three major geographical terraces, earthquakes occur very frequently in these geological marginal areas.

May you be safe!

[1] Bai Mingkun, Chevalier Marie-Luce, Li Haibing, Pan Jiawei, Wu Qiong, Wang Shiguang, Liu Fucai, Jiao Liqing, Zhang Jinjiang, Zhang Lei, Gong Zheng. Study on strike-slip rate and regional strong earthquake hazard of the Qianning section of the Xianshuihe fault zone during the late Quaternary[J]. Acta Geologica Sinica, 2022, 96(07): 2312-2332. DOI: 10.19762/j.cnki.dizhixuebao.2022144.