Macroseismic Manifestations of the Disastrous 2008 Wenchuan Earthquake (MS = 8.0) According to the Study of Surface Seismodislocations

Resumo

On May 12, 2008, a catastrophic earthquake with magnitude M_S = 8.0 occurred in Wenchuan County, Sichuan, China. Its epicenter was located in the Longmen Shan mobile tectonic belt and its hypocentral depth was 14 km. The mainshock produced the system of primary seismodislocations (ruptures) on the surface: Beichuan–Yingxiu Fault of more than 240 km long, Guanxian–Anxian Fault of about 70 km long, and Xiaoyudong Fault of 7 km long. The maximum measured vertical and dextral displacements along the faults were up to 10 m and 4.8 m, respectively. The rupturing and manifold landslides, rockfalls, and rock avalanches that followed caused significant destructions in a number of localities, damaged roads, and led to massive human deaths. Data collected on the distribution of primary and secondary effects of earthquakes has helped outline zones with shaking intensities of IX, X, and XI. Notably, the seismic intensity of surface shaking was anomalously low even close to the fault system. We have conducted a comprehensive seismotectonic study of the epicentral zone of the Wenchuan earthquake. When assessing the shaking intensities, we apply the Earthquake Environmental Effects (EEE) scale developed in the framework of INQUA project (2004–2016). A comparison shows that the isoseismals identified from macroseismic data on damages in buildings and structures coincide with the locations of zones with various seismic effects on the EEE scale.