High-resolution topographic and geomorphic data are important basic data for the study of active structures. Here, multisource remote sensing data were used to reinterpret the active faults in the northern segment of the Red River Fault (China). First, we obtained airborne light detection and ranging (LiDAR) data, high-resolution GaoFen-7 (GF-7) remote sensing image data, and historical aerial photographs, and a high-resolution digital elevation model (DEM) was generated based on the airborne LiDAR data and GF-7 data. According to the remote sensing interpretation, the main active faults were identified. We subsequently verified the faults in the field and constrained the geographic locations. The current activity was confirmed to be dominantly normal faulting, with some dextral strike-slip components, and the latest active age was the Late Holocene. It reflects the coordination of structural deformation between the rotation of the secondary block and the sliding of the boundary fault within the Sichuan–Yunnan Block. The results show that airborne LiDAR and GF-7 remote sensing data have a great application value in providing high-resolution topographic and geomorphologic data for the study of active structures. The comprehensive application of multisource remote sensing data can greatly improve the reliability of active fault interpretations and provide a reference for follow-up research within the study area.

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.

Quantifying the geometrical and kinematic aspects of faults within the Tian Shan Mountain Range is crucial for investigating the tectonic deformation patterns in the region. Through remote sensing image analysis using GaoFen-7 (GF-7) data and field geological surveys, we determined the geometric distribution and fault properties of the Kalawenguquan fault. The newly discovered Kalawenguquan fault spans more than 400 km and mainly strikes in the NEE direction, with some localized segments in the NE direction. The fault plane dips southward at angles ranging from 55 degrees to 85 degrees . The Kalawenguquan fault is a recently discovered Holocene active fault in the Tian Shan and is a thrust and left-lateral strike-slip fault. Based on geological survey findings and sediment dating data from the late Quaternary, the Kalawenguquan fault has a vertical sliding rate of approximately 0.41 mm/a. The left-lateral strike-slip rate was calculated to be 0.6 - 1.4 mm/a. We detected that at least two paleoseismic events occurred on the fault since 5.4 +/- 0.4 ka. In the range of 41 degrees-45 degrees latitude, 45 % of the crustal shortening in the Tian Shan is absorbed by the internal structure.

The Red River Fault Zone is a large-scale right-lateral strike-slip fault zone with relatively strong activity during the Quaternary Period. This fault, located on the southeastern margin of the Qinghai-Tibetan Plateau, plays a key role in the extrusion, rotation and escape of the continental blocks constituting the Qinghai-Tibetan Plateau. Furthermore, this fault represents the southwestern boundary of the Sichuan-Yunnan Block, which has experienced strong deformation and frequent seismic activity. The northern segment of the Red River Fault Zone is the most active part of the whole fault. However, surface erosion and vegetation coverage have obscured the activity of the northern segment; therefore, the study of its activity has obviously been insufficient. There is still controversy over whether all the secondary faults on the northern segment are active Holocene faults. Studying the activity characteristics of the northern segment, which is densely populated, is particularly important for seismic risk prevention in this area. Based on remote sensing interpretations and field geological surveys, this paper describes the latest activity characteristics of the Cangshan Piedmont Fault, Fengyi-Dingxiling Fault and Midu Basin Margin Fault, including their spatial distributions and kinematic characteristics. According to the ages of the offset strata in profiles, the above three secondary faults were all active in the late Holocene. The latest active age of the Cangshan Piedmont Fault was later than 543-494 cal BP, and two palaeoseismic events that occurred in this section during the Holocene occurred at 2700 and 473 cal BP. The latest active age of the Fengyi-Dingxiling Fault was later than 2760-2700 cal BP; in this section, one Holocene palaeoseismic event occurred between 1777 cal BP and 2730 cal BP, another occurred between 2730 cal BP and 5664 cal BP, and the third occurred between 6449 cal BP and 8360 cal BP. The latest active age of the Midu Basin Margin Fault was later than 558-510 cal BP, and two Holocene palaeoseismic events occurred later than 2318-2114 cal BP and 558-510 cal BP. Based on the results of this paper and previous studies, we believe that the Fengyi-Dingxiling Fault on the northern segment of the Red River Fault Zone is at risk for future strong earthquakes. Additionally, abundant geological and geomorphologic evidence suggests that the northern segment is dominated by normal faults, reflecting the local strain response to secondary clockwise rotation of the Sichuan-Yunnan Block along the boundary fault. This finding is in line with the eastwards extrusion and escape of materials on the QinghaiTibetan Plateau caused by the northwards and northeastwards pushing of the Indian Plate. To a certain extent, these observations reflect the tectonic deformation coordination between block rotation and boundary fault slip in the Sichuan-Yunnan Block in the context of continental block extrusion on the Qinghai-Tibetan Plateau.

Based on a digital elevation model (DEM) and GIS technology, we extracted and analyzed stream geomorphic indices—such as the slope, relief degree of the land surface (RDLS), hypsometric integral (HI) and channel steepness index (ksn)—of the Cangshan Piedmont Fault, Fengyi–Dingxiling Fault and Midu Basin Margin Fault in the northern segment of the Red River Fault Zone. This work indicates that all the stream geomorphic indices show higher values, with the highest values along the Cangshan Piedmont Fault, followed by the Fengyi–Dingxiling Fault, and the lowest values along the Midu Basin Margin Fault, forming a decreasing trend from north to south. Based on lithology, climate and tectonics, we infer that neotectonic activity is the main factor controlling the development of the drainage geomorphology. The results show that the northern segment of the Red River Fault Zone is highly active and that the activity level shows a decreasing trend from north to south. The results of this study are consistent with previous conclusions that the overall activity of the Red River Fault Zone weakens from north to south, and the activity in the northern segment has been the most intense since the Late Pleistocene.

The response of the stream geomorphic index to fault activity is important for assessing the regional seismic hazard. The data used in this paper are 12 m resolution TanDEM-X data. The Fill tool in the Hydrology toolset in ArcGIS 10.5 was used to first process the digital elevation model (DEM), then analyse the flow direction of the DEM after filling and finally extract streams with catchment areas of more than 9 km2. Based on the DEM spatial analysis, the stream geomorphic index of the Lianfeng–Ningnan segment (LNS) of the Lianfeng fault was extracted, including the stream length gradient (SL) and the hypsometric integral (HI). This information, combined with the analysis of typical field geomorphology and terrace profiles, was used to define the fault activity period. To analyse the activity characteristics of the LNS, the LNS was divided into northern (Lianfeng to Jinyang), middle (Jinyang to Duiping town) and southern segments (Duiping town to Ningnan). The stream geomorphic index showed spatial variations, with mean SL and HI values of 384 and 0.45, respectively, in the northern segment; 175 and 0.41, respectively, in the middle segment; and 378 and 0.45, respectively, in the southern segment. These results indicate that the northern and southern segments of the LNS are more active than the middle segment, that there is little difference between the northern and southern segments, and that the activity of the middle segment is relatively weak. By comprehensively analysing the lithology, climate and tectonics in the LNS region, we conclude that tectonics are the main factor controlling the stream geomorphology in the LNS region. Based on this information and the analysis and dating of field geomorphology and terrace profiles, we found that the Lianfeng fault was active in the Holocene, which is consistent with the latest research results.

The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abun-dant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identifi-cation of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.