# Quaternary Segmentation Characteristics of the Hunhe Fault, Northeast China
## 2 Geological Background
### The Quaternary Activity of the Hunhe Fault  
Analysis suggests that the Chifeng-Kaiyuan fault near the Mishan-Dunhua fault is an extension of its eastern segment, composed of 3-4 nearly parallel branching faults trending from NWW to near east-west, with a length of 80-100 km. The fault morphology and structure are clear, with significant surface exposure and a damage zone width of 1-2 km. The linear valleys and steep landforms form along the fault, providing geological and geomorphological evidence of MIS 20-103-MIS6-19 activity [14]. The Yilan-Yitong fault, which intersects with the Hunhe fault, represents its Liaoning section and consists of 2-4 parallel branch faults with a length of nearly 200 km, forming a graben structure [19; 20]. This fault controls the development of basin structures and the distribution of Quaternary strata, exhibiting discontinuous exposure and well-developed fault gouge [21; 22]. The Suzihe fault intersects the Hunhe fault in the Nanzamu Basin and is truncated by the Hunhe fault. It has a relatively shallow cut and belongs to a basement fault [23]. The fault extends nearly 200 km and has a shovel-like surface distribution, with the western section near the Hunhe fault trending NW over approximately 70 km. This fault controls the development of the Suzihe River, forming clear geomorphic valleys. The western section of the Suzihe fault consists of 2-4 branching faults, exhibiting a composite branching structure. Within the fault zone, early Quaternary formations of thin cataclasite and siltstone have been observed, but no fault gouge is noted, showing a weaker activity level. The Xiahada fault intersects with the Hunhe fault near Zhangdang at the eastern end of the Fushun Basin. It comprises two NE-trending compressive torsional faults, ranging from 40 to 65 km in length, exhibiting a linear or arcuate fault structure and forming linear valleys along the fault. The morphology of the fault damage zone is complex, with a very small scale of newly active tectonic belts from the Quaternary, and the most recent activity also dates to the early Quaternary, showing a weaker level of activity. An overview of the Quaternary sedimentation and geomorphological development characteristics along the Hunhe fault reveals that the Quaternary strata can be broadly divided into 4 to 5 distinctly different sedimentary areas, corresponding to the significant differences in terrain that can also be categorized into 4 to 5 geomorphological terraces. The area near Shenyang lies at the northeastern edge of the lower Liaohe Plain, characterized by a gently sloping plain with low elevation, ranging from 25 to 65 m above sea level and a gradient of 1:1500. It features continuous and complete Quaternary strata from MIS 20-103 to Q4, with a large scale and relatively uniform topographical undulation along the fault zone and its flanks [24]. The Fushun Basin section is located in the transitional zone between the western lower Liaohe Plain and the eastern Liaodong Mountains. It forms a distinct geomorphological contrast between the flat, open, gently undulating east-west graben basin and the low mountain-hill areas to the north and south. The terrain of the Fushun graben basin rises in a stair-step manner compared to the lower Liaohe Plain, with an elevation increase of about 30-40 m and a gradient of 1:850. The Quaternary integrity within the basin is relatively poor, and its scale is significantly reduced compared to that near Shenyang. The low mountain-hill areas on both sides of the basin exhibit noticeable topographical relief, with exposed bedrock and undeveloped Quaternary strata. The elevation in the northern side of the Panhe Neotectonic Zone generally ranges from 120 to 450 m, with a maximum of around 500 m; near the Hunhe fault, it ranges from 120 to 350 m [24; 25].