Abstract:The NW-striking fault of the Minjiang River is an important seismic structure in the Fujian coastal area. Previous research has focused on the downstream section of the Minjiang fault, but little attention has been given of the fault location, geological features, and the latest active age of the upstream section. The upstream section is distributed between the city of Nanping and Xiongjiang County and the city of Minjiang. Based on a detailed field geological survey, we gained a new understanding of the distribution characteristics and activity of the upper reaches of the Minjiang River. The results show the following: (1) This area can be divided into two segments, with the western segment, located between the city of Nanping and the town of Taiping, being composed of two parallel right-lateral strike-slip normal faults, which strike NW300°. The eastern segment is located in the Xitang area, and has a NW300° strike-slip normal fault. (2) The fault at the upper reaches of the Minjiang River exhibits characteristic multiperiodic activity, at the early stage, mainly striking NW330°, and is characterized as a compresso-shear type. Its latest active time was in the pre-Quaternary. At the later stage, the fault was mainly striking NW300° and is characterized as a strike-slip type, as transtensional properties may still have been active in the early Quaternary.
