ABSTRACT
Two Ms 5.0 earthquakes occurred in Tonghai, Yunnan Province, at 01:44 am on August 13 and 03:50 am on August 14, 2018. The China Seismic Network measured the surface wave magnitudes of both earthquakes as Ms5.0, with almost the same epicenter location, and epicenter depths of 7.0 km and 6.0 km, respectively. It is generally believed that the rupture directions of these two earthquakes was NE to SW, and they are caused by NE–SW direction buried faults by relocation of earthquake sequences. Although the surface wave magnitude was the same, the moment magnitudes were different. The strong motion records obtained in the near field also clearly reflected the difference in the intensity and the rupture direction of the two earthquakes. Eliminating the site effect of the earth surface structure, the free outcrop bedrock records, which are twice the seismic incident waves of underground bedrock, were inverted by equivalent linearization method. The new distributions of ground seismic intensity on the free outcrop bedrock site were obtained. According to the distribution map, it is obvious that the August 13, 2018 Tonghai Ms5.0 earthquake has a NE–SW direction buried fault. But the August 14, 2018 Tonghai Ms 5.0 earthquake has a NW–SE direction buried fault.
