Abstract The vertical deformation field of the epicentral region before and after the 2013 Minxian-Zhangxian MS6.6 earthquake is obtained by using the leveling data of Lanzhou-Tianshui-Wudu regional leveling from 1973 to 2014. The results show that: (1) From 1999~2006 regional vertical deformation field, the earthquake is located at the transition zone from the uplift zone of NNW-NWW to the subsidence zone near EW, and is also a reflection of the tectonic activity difference zone between the Minshan and Qinling mountains. (2) From the evolutionary process of the Longxi-Minxian leveling section along the NNE direction near the west of the epicenter, the vertical deformation has obvious characteristics of stage deformation, and it finally shows the mutation before the earthquake. Among them: in 1973~1993, there is a pressure uplift area with the maximum rise of nearly 40 mm between Zhangxian and Minxian. The uplift area disappears and turns flat. the overall profile of the section fluctuates, and the range is about 10 mm from 1993~2008. There is no obvious vertical difference movement on both sides of the west Qinling fault and Lintan-Tanchang fault. A subsidence gradient zone near 40 km appears on both sides of the Lintan-Tanchang fault between Zhangxian and Minxian relative to the Longxi basin in 2008~2011. Among them, three leveling points, Wuding 80, Wuding 78 and Wuding 77, which are within 16 km of the epicenter, have a downward mutation synchronously, close to or more than twice the normal range of changes since 1973. Relative to Longxi basin, the recovery between Zhangxian and Minxian is mainly thrusting and uplifting. In 2011~2014, the deformation zone on both sides of the Lintan-Tanchang fault before the earthquake did not exist, and the above 3 leveling points are also restored to the interval before the earthquake. (3) On the basis of summing up the deformation precursors before Minxian-Zhangxian MS6.6 earthquake, in view of the current controversy about the characteristics of deformation acceleration or mutation before the earthquake, we infer that if the spatio-temporal scale of the deformation data is sufficient, at least the moderate strong earthquakes in some tectonic regions can be caught before the earthquake.
ZHANG Sixin,SU Xiaoning,LI Peng et al. Sudden Change before Earthquake-Seismogenic Characteristics of 2013 Minxian-Zhangxian MS6.6 Earthquake as Reflected by Leveling Data[J]. jgg, 2019, 39(8): 771-776.
ZHANG Sixin,SU Xiaoning,LI Peng et al. Sudden Change before Earthquake-Seismogenic Characteristics of 2013 Minxian-Zhangxian MS6.6 Earthquake as Reflected by Leveling Data[J]. jgg, 2019, 39(8): 771-776.
