5. 12 What is the main cause of Wenchuan earthquake?
What caused the Wenchuan earthquake?
Because Wenchuan is located in the North-South seismic belt, a major seismic belt in China. There are great differences in geological distribution, crustal thickness and crustal movement speed between the east and the west of China, and the earthquake occurred in this zone with the greatest difference between the east and the west, that is, the north-south seismic belt-including from Ningxia through eastern Gansu, western Sichuan and Yunnan, which is an earthquake-intensive belt.
The main causes of Wenchuan earthquake:
The main reason of Wenchuan earthquake is that Yingxiu fault, the main boundary fault at the front of Longmenshan structural belt, thrusts from west to east, and the fault plane is inclined to the west with an inclination angle of about 60. According to the distribution of the main earthquake and aftershocks, it is preliminarily concluded that this earthquake belongs to one-way rupture earthquake, and the rupture direction is mainly controlled by the northeast structural belt of Longmen Mountain.
The macro explanation is that "the Indian Ocean plate collided with the Eurasian plate from south to north, and the collision zone arched the Qinghai-Tibet Plateau." Professor Ni Sidao from the School of Earth and Space Sciences of China University of Science and Technology told Southern Weekend reporter, "The Qinghai-Tibet Plateau is rising, but it is also moving to the northeast, squeezing the Sichuan Basin to slide to the northeast. The Wenchuan earthquake occurred in the southeast of the Qinghai-Tibet Plateau."
According to the Catalogue of Strong Earthquakes in China compiled by Forecast Management Office of Monitoring and Forecasting Department of Seismological Bureau of China 1999 in September, there were 8 earthquakes with magnitude above 7 1800 in Sichuan, among which 8 earthquakes with magnitude above 7 occurred since1800. An earthquake of magnitude 7.6 occurred in Luhuo, Sichuan in June of 5438+0973, and an earthquake of magnitude 7.2 occurred in Songpan-Pingwu, Sichuan three years later. In 2002, Chen Xuezhong, a researcher at the Institute of Geophysics, Seismological Bureau of China, analyzed the risk of earthquakes of magnitude 7 or above in Sichuan Province: "There has been no strong earthquake in Sichuan for a long time. In the words of the industry, it is called no earthquake, which means there is no strong earthquake. According to historical experience, the longer the absence, the more likely it will happen in the future. This is a qualitative estimate. " In this context, Chen Xuezhong studied the earthquake risk in Sichuan. From the historical experience, a few years before a strong earthquake of magnitude 7 or above occurred in Sichuan, there were major earthquakes around it. According to this phenomenon, an earthquake of magnitude 8. 1 occurred in Kunlun Mountain in 200 1 year. If this rule continues, this kind of earthquake will happen in Sichuan in a few years.