# Quaternary Segmentation Characteristics of the Hunhe Fault, Northeast China
## 5 Discussion
### Seismic Activity of Zhangdang-Nan Zamu Segment  
The fault segment lies in the Liaodong Mountains, where the macroscopic landscape is dominated by eroded and denuded low mountains and hills. There is no development of Quaternary faulted basins along the fault zone, but the western end borders the Fushun Basin along the Xiaohada fault, while the eastern end borders the Nanzamu Basin along the Suzihe fault, forming faulted or stepped zones between them. The primary branches can create stable, continuous NEE-oriented valleys, linear depressions, or similarly aligned piedmont alluvial fans and colluvial skirts. The slopes and scarps on either side of the valleys are clearly defined and well-connected. Additionally, a series of small, NEE-oriented erosional and depositional terraces can be observed along the mountain fronts. These terraces reveal exposures of the faulted fracture zone when traced along these scarps and slopes. Along the fault, strip-like Quaternary deposits are found in valleys, depressions, and on alluvial fans, colluvial skirts, and erosional terraces, indicating that the fault controls their distribution. However, the Quaternary sequence in this region is incomplete, with a general absence of MIS6-19 and earlier strata. Although the fault has little overall impact on the MIS 2-5-4 strata, observations in some profiles indicate fault creep, causing minor displacements or disturbances in these layers. There is minimal impact on the upper MIS 2-5 to Qh strata, and no fault scarps are observed near the surface. The surface geomorphic units, including alluvial fans, colluvial skirts, and erosional terraces, mostly correspond to Qp3 Qh strata. In some areas, the fault is concealed beneath these geomorphic units, without forming observable fault scarps or micro-relief features. The gravity field along the Shenyang segment of the Hunhe fault exhibits a negative anomaly gradient zone, with noticeable differences between the northern and southern sides (Figure 11). This gravity anomaly pattern reflects variations in subsurface density, likely related to the fault's structural characteristics. The magnetic field in the area shows a stable negative anomaly, with regular contours aligned along the fault, indicating a consistent magnetic signature that mirrors the fault's orientation. Additionally, crustal thickness increases from west to east and from south to north, suggesting regional variations in the Earth's crustal structure, possibly influenced by the fault zone's tectonic history. In terms of seismic activity, the Zhangdang-Nanzamu segment of the Hunhe fault stands out for its relatively weak seismicity when compared to the Shenyang and Fushun segments. Since 1970, only one earthquake exceeding magnitude 3.0 has been recorded along this segment, indicating low-intensity and infrequent seismic events. The spatial distribution of these seismic events does not show a clear pattern, and there is no evident tectonic relationship between the observed seismic activity and the Hunhe fault. This lack of correlation suggests that the fault, despite its significant geological features, does not exhibit a strong seismic signature in this area, highlighting the complexity of fault dynamics and the varied behavior of fault segments across the region. The Zhangdang-Nanzamu segment of the Hunhe fault has experienced multiple phases of different types of tectonic activity. While early activity was intense, the fault's activity decreased significantly during the Neogene and into the Quaternary. The compressional-thrust and imbricate structures formed before the Quaternary, along with associated faulted rocks, structural traces, and frameworks, have largely been preserved and remain substantial in scale. These coexist with the relatively smaller-scale products of more recent Quaternary activity within the fault zone. The recent tectonic activity could either continue along earlier faulted zones or follow new paths.