Abstract：Based on the two-dimensional finite element method, we use the contact element to simulate the discontinuous fracture process of fault zone, and establish the near-field strong ground motion estimation model of the Jiuzhaigou M7.0 earthquake in Sichuan on August 8, 2017. We also study the key source parameters such as stress drop and yield stress. Based on the reliability test of ground motion parameters using the actual observation waveforms provided by the national strong earthquake data center, we give the PGA distribution, and discuss the characteristics and mechanism of directional effect of near-field strong ground motion. The results show that: 1) With the increase of yield stress and stress drop parameters of the source contact element, the horizontal PGA increases as a whole, and the influence of the former on strong ground motion is more significant. When the stress drop is 8.5 MPa and the yield stress is 4.0 MPa, the relative error percentage of strong ground motion simulation results is less than 40% on the whole, and the relative error of 51JZB and other near-field strong seismic stations is less than 5%. 2) The contour of horizontal PGA simulation results of the Jiuzhaigou M7.0 earthquake is generally elliptical, and the major axis of the ellipse is in good agreement with the strike of seismogenic fault. The maximum value of PGA near the epicenter is about 720 Gal, and decreases with the increase of epicenter distance. The PGA dropped by 16.67% and 22.72% respectively when cross the north section of Longriba fault and Xueshanliangzi fault. The isolation effect of fault zone may be related to the transmission reduction of ground motion along the fault plane.
ZHANG Yanfang,HU Qizhi,ZHANG Jie et al. Estimation of Strong Ground Motion and Directional Effect of the 2017 Jiuzhaigou M7.0 Earthquake[J]. jgg, 2023, 43(11): 1136-1142.
