GPS data were used to study the interseismic slip distribution and locking characteristics of the mid-southern segment of the Tanlu fault zone

The central and southern section of Tanlu fault zone is a section with frequent seismic activity and dense population distribution.Along the fault are infrastructure such as high-speed rail and the South-north Water Diversion project, as well as world heritage sites such as the Grand Canal, ancient city ruins and cultural landscapes. If a strong earthquake occurs in the future, it may cause great social impact and property losses.It is necessary to have a clear understanding of the current activity characteristics and potential seismic risk of fault zone to reduce the loss of earthquake disaster scientifically and reasonably.However, there are few data on its current activity characteristics through geodetic data.Based on GPS observation data from 1991 to 2020, the characteristics of fine slip distribution between present earthquakes in the mid-southern segment of the Tanlu fault zone are retrieved based on the fastest descent method. On this basis, the lock degree and slip rate deficit characteristics of this section are obtained；Finally, by comparing the surface strain results from 1991 to 2007 and 2013 to 2020, the differences of deformation characteristics between the two phases of the mid-southern segment of the Tanlu fault zone are analyzed.The results show that the interseismic sliding rate of the mid-southern segment of the Tanlu fault zone is 0 ~ 1 mm·-1，In the northern Tancheng-Sihong section, it showed right-handed thrust, and the sliding rate was between 0.2 ~ 1 mm·-1；The Sihong - Tongcheng section of the southern section is dextrorotally stretched, and the sliding rate is between 0 and 0.5mm.The degree of blockage in the mid-southern segment of the Tanlu fault zone is segmented along fault strike.In the north section, the locking depth of Changyi-Tancheng section was relatively high, with the deepest reaching 32 km,and the maximum compression-slide loss rate reaching -1mm·a-1；Tancheng-Wangji closure coefficient decreased significantly, with a concentrated distribution between 0.2 and 0.7. The Wangji-Jiashan section has a high degree of closure, small and medium earthquakes are not active, and it is the unruptured section, which is more prone to stress accumulation.