Calculation of the Co-seismic Effect of Ms8.1 Earthquake, Apirl 25, 2015, Nepal

Abstract:

On April 25, 2015, an Ms8.1earthquake occurred in Nepal, which caused a rupture zone of over 100 kilometers developing southeast and the epicenter was only 70 kilometers away from Kathmandu, the capital of Nepal, causing heavy casualties in Nepal. Based on the elastic dislocation theory and global finite element method, an equivalent volume force of layered co-seismic crustal computation model is set up. And based on the USGS and CEA fault slip models, we calculate the co-seismic displacement, stress field and ΔCFS caused by Nepal Ms8.1 earthquake. The calculation result shows that: (1) Nepal Ms8.1 earthquake is a typical low-angle thrust earthquake and co-seismic displacement caused by the earthquake is mainly concentrated in the horizontal plane and centered in the surrounding area of Katmandu, the capital of Nepal. The maximum co-seismic horizontal slippage under USGS slip model and CEA slip model is about 4m and 2m respectively; compared with the east-west and vertical displacement caused by the earthquake, the horizontal displacement in south-north direction is larger, which is reflected as the handing wall diving southward; the computed result based on CEA model and USGS models show that the maximum displacement of southward hanging wall is 1.2m and 3.47m respectively; (2) Nepal is located in the collision and compression fault zone of Eurasian Plate and Indian Plate, with well-developed tectonic fault. The seismogenic fault of Ms8.1 earthquake may belongs to the MHT fault zone. The ΔCFS induced by the earthquake is positive in the seismic source area and the maximum of ΔCFS can reach 0.1MPa, showing there still more dangerous; (3) Nepal Ms8.1 earthquake has a certain impact on the Tibet region of China. According to the seismogenic fault of Ms8.1 earthquake, the stress change of 1kPa in Yaruzampbo region and Lhasa block can be calculated, which may even reach 10kPa; Shigatse and Lhasa are located in the area in where the ΔCFS increases. Close attention shall be paid to the possibility of induced earthquake in Lhasa and Shigatse.