Sichuan Earthquake: A Historical Earthquake

Sichuan earthquake
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Sichuan Earthquake
Sichuan is a province that occupies the Sichuan basin and Tibetan plateau in southwest China. In May 2008, the province was struck by a historic earthquake which destroyed the infrastructures, caused landslides, caused debris flow, caused dam flow and also caused landslide lakes. The measure of the earthquake was 8.0 Ms and7.9 Mw with its epic center 80km from Chengdu city. It claimed more than 69,000 lives and made 4.8 million people homeless (Wu, Jidong, et al., 2008). Geohazards of the earthquake contributed about 1/3 of the death toll. This particular earthquake has a record of having the largest number of geohazards which include 110,000 km2 being occupied by 800 quake lakes and about 200,000 landslides. Months after the main shock, strong aftershock which further caused casualties and damages continued to be experienced. Before the main shock, the people of Sichuan were caught unaware as their houses and schools had little resistance to seismic. They have built them without consideration of such an event in the future. Consequently, the fatality of the earthquake which occurred in May 2008 was severe.
The study done by China earthquake administration indicated that the earthquake occurred on a Longman Shan fault while the thrust occurred along Indi-Australian plate and Eurasian plate’s border. The seismic activity of the earthquake was concentrated in Yingxiu-Beichuan fracture also known as mid-fracture (Yang, Yang, Duan, Chen, & Dekkers, 2016). This study also showed that the rapture lasted for 2 minutes with most of the energy being released in the first 80 seconds. The rapture started in Wenchuan and with a speed of 3.1km/hr. propagated a distance of 300km toward 49°north east. The maximum displacement according to the study was 9m with focus deeper than 10km.
According to the survey done by the United States geological survey, it was possible that the displacement along the fault could be of about 9 meters, with the length of 240km and depth of 20km. According to the study, there was a generation of deformation on the surface greater than 3m after the earthquake. There was also stress increment, which could lead to a similar occurrence in the southwestern and northeastern end of the fault.
Figure to show the location of Chengdu quake
Yuji Yagi did a study has shown that it was also possible for the earthquake to happen in 2 stages. According to his study, the Longman Shan fault ripped twice. First by 6.5m followed by the second 3.5m. The results of his study also shown that the earthquake lasted for 2 minutes. He attributed the earthquake to the density of the population together with the shallow epic Centre.
The fault system of The Longman Shan was located in Tibetan plateau on the eastern border. The earthquake occurred at two imbricated structures of the fault system of long men Shan. The two imbricated structures are Guan Xian and Beichuan Fault. Beichuan Fault slipped about 3.5M vertical and parallel to the fault in the epicentral area. Horizontally to the fault, the Beichuan Fault slipped by 4.8M (Nakata, Otsuki, & Khan, 1990). In the area of approximately 30Km, the surface on Beichuan slipped in abou...