Preliminary finite difference simulation of long-period strong ground motions for the Yangbi MS6.4 earthquake

Abstract

According to the geological and geomorphic characteristics of the Sichuan-Yunnan area, previous geological data and the preliminary inversion results of source parameters of the Yangbi MS6.4 earthquake in 2021, we established a three-dimensional velocity structure model and studied the long-period ground motion of the Yangbi earthquake by using the three-dimensional finite difference method. Meanwhile, we arranged 36 observation points in and around the Yangbi earthquake area and obtained the velocity response spectra of all observation points with a damping ratio of 5%. The three-component velocity time histories of 6 observation points are also given, The results show that: (1) the simulated velocity peak has exceeded 25 cm/s, which is consistent with the intensity of 8 near the actual Yanghe area; (2) Affected by the distribution of fault slip, the horizontal component of velocity is more widely distributed in the northwest, and the attenuation speed is significantly slower than that in the southeast. In the meizoseismal region , the attenuation of ground motion from the northeast to southwest is also slower. The directivity effect has a significant effect on the peak value and distribution range; (3) The characteristic period of velocity response spectrum of observation points are distributed in the range of 1 ~ 3 s, which may cause serious damage to large buildings near the area due to resonance effect. It is necessary to further study the Yangbi earthquake to have a more detailed understanding of the long-period ground motion of the Yangbi earthquake.

Keywords

• yangbi ms6.4 earthquake
• long-period strong ground motion
• finite difference method
• numerical simulation