Interseismic slip distribution and locking characteristics of the mid-southern segment of the Tanlu fault zone

Abstract

Abstract The central and southern sections of the Tanlu fault zone experience frequent seismic activity and have a dense population distribution. 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, is located along the fault. A strong earthquake occurring in the future may cause significant social impacts and property losses. It is necessary to clearly understand the current activity characteristics and potential seismic risk of the fault zone to scientifically and reasonably reduce the losses of earthquake disasters. However, there are little data on its current activity through geodetic data. Based on GPS observation data from 1991 to 2018, the fine slip distribution characteristics between present earthquakes in the mid–southern segment of the Tanlu fault zone were retrieved based on the fastest descent method. On this basis, the lock degree and slip rate deficit characteristics of this section were obtained. The differences in the deformation characteristics between the two phases of the mid–southern segment of the Tanlu fault zone were analysed by comparing the surface strain results from 1991 to 2007 and 2013 to 2018. The results show that the interseismic sliding rate of the mid–southern segment of the Tanlu fault zone was 0–1 mm·a-1. The northern Tancheng–Sihong section showed right-handed thrust, and the sliding rate was 0.2–1 mm·a-1. The southern Sihong–Tongcheng section was stretched left–right, and the sliding rate was 0–0.5 mm.a-1 The degree of blockage in the mid–southern segment of the Tanlu fault zone was segmented along the fault strike. In the northern section, the locking depth of the Changyi–Tancheng section was relatively high, with the deepest reaching 32 km, and the maximum compression-slide loss rate reached -1 mm·a-1; the 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, being more prone to stress accumulation.