Study on the late quaternary activity of the Jinyang-Ningnan segment of the Lianfeng fault zone

Abstract

The Lianfeng fault zone is located at the junction of the Daliangshan subblock and the South China block and is the southern boundary of the Daliangshan subblock. It is a very active tectonic area, which is of great significance to understanding its seismogenic environment. However, there are relatively little existing data on its activity and the timing of its latest activity. In the Jinyang-Ningnan segment of the Lianfeng fault zone along the Jinsha River, remote sensing image interpretation, field geologic surveys, high-precision drone measurements, and sample dating indicate that the river terraces T1 (the lowest, 15–40 m above the local river level) and T2 (60–90 m above the local river level) developed in the mid-Holocene and late Pleistocene. This indicates that the Jinsha River basin has been strongly downcutting since the Late Pleistocene. The fault profiles are mainly exposed in the T1 and T2 terraces of the Jinsha River. Based on this information in combination with the fault characteristics of the sedimentary profile and stratigraphic dating, it is believed that the Lianfeng fault zone was active at least along the Jinyang-Ningnan segment, with the latest activity occurring no earlier than the early to mid-Holocene.