The 2014 Jinggu M6.6 earthquake attacked the Jinggu area where few historical earthquakes had occurred and little study has been conducted on active tectonics. The lack of detailed field investigation on active faults and seismicity restricts the assessment of seismic risk of this area and leads to divergent view points with respect to the seismotectonics of this earthquake, so relevant research needs to be strengthened urgently. In particular, some studies suggest that this earthquake triggered the activity of the NE-trending faults which have not yet been studied. By the approaches of remote sensing image interpretation, structural geomorphology investigation and trench excavation, we studied the late Quaternary activity of the faults in the epicenter area, which are the eastern margin fault of Yongping Basin and the Yixiang-Zhaojiacun Fault, and drew the conclusions as follows:
(1)The eastern margin fault of Yongping Basin originates around the Naguai village in the southeastern margin of Yongping Basin,extending northward across the Qiandong, Tianfang, and ending in the north of Tiantou. The fault is about 43km long, striking near SN. The linear characteristic of the fault is obvious in remote sensing images. Structural geomorphological phenomena, such as fault troughs, linear ridges and gully dislocations, have developed along the faults. There are several dextral-dislocated gullies near Naguai village, with displacements of 300m, 220m, 146m, 120m and 73m, respectively, indicating that the fault is a dextral strike-slip fault with long-term activity. In order to further study the activity of the fault, a trench was excavated in the fault trough, the Naguai trench. The trench reveals many faults, and the youngest strata offseted by the faults are Holocene, with ¹⁴C ages of(1 197±51)a and(1 900±35)a, respectively. All those suggest that it is a Holocene active fault.
(2)The Yixiang-Zhaojiacun Fault starts at the southeast of the Jinggu Basin, passes through Xiangyan, Yixiang, Chahe, and terminates at the Zhaojiacun. The total length of the fault is about 60km, and is a large-scale NE-trending fault in the Wuliangshan fault zone. Four gullies are synchronously sinistrally dislocated at Yixiang village, with the displacements of 340m, 260m, 240m and 240m, indicating that the fault is a long-term active sinistral strike-slip fault. A trench was excavated in a fault trough in Yixiang village. The trench reveals a small sag pond and a fault. The fault offsets several strata with clear dislocation and linear characteristic. The thickness of strata between the two walls of fault does not match, and the gravels are oriented along fault plane. The offset strata have the ¹⁴C age of(2 296±56)a, (3 009±51)a, and(4 924±45)a, respectively, and another two strata have the OSL age of(1.8±0.1)ka, (8.6±0.5)ka respectively, by which we constrained the latest paleoearthquake between(1.8±0.1)ka(OSL-Y01)and(378±48)a BP(CY-07). This again provides further evidence that the fault is a Holocene fault with long-term activity.
(3)Based on the distribution of aftershocks and the predecessor research results, the 2014 Jinggu M6.6 earthquake and the M5.8, M5.9 strong aftershocks are regarded as being caused by the eastern margin fault of Yongping Basin, which is part of the Wuliangshan fault zone. The seismogenic mechanism is that the stress has been locked, concentrated and accumulated to give rise to the quakes in the wedge-shaped area near the intersection of the SN and NE striking faults, which is similar to the seismogenic mechanism in the southwest of Yunnan Province.

With the development of photogrammetry technology and the popularity of unmanned aerial vehicles (UAVs)technology in recent years, using UAV photogrammetry technology to rapidly acquire high precision and high resolution topographic and geomorphic data on the fault zone has gradually become an important technical means. This paper first summarizes the basic principle and workflow of a new digital photogrammetry technology, SfM (Structure from Motion), which is simple, efficient and low cost. Using this technology, we conducted aerial image acquisition and data processing for a typical fault landform on the northern of Caka Basin in Qinghai. The digital elevation model (DEM)with 6.1cm/pix resolution is generated and the density of point cloud is as high as 273 points/m². The coverage area is 0.463km². Further, the terrain and slope data parallel to the fault direction are extracted by topographic analysis method, and combined with the contour map and the slope diagram generated by the DEM, a fine interpretation and quantitative study of complex multilevel geomorphic surfaces is carried out. Finally, based on the results of sophisticated interpretation of geomorphology, we got the vertical displacements of the T₁ terrace to the T₃ terrace as (1.01±0.06)m, (1.37±0.13)m and (3.10±0.11)m, and the minimum vertical displacements of the T₄ terrace and the T₅ terrace as (3.77±0.14)m and (5.46±0.26)m, respectively, through the topographic profile data extracted by DEM. Such vertical displacement parameters are difficult to obtain directly by traditional remote sensing images, which shows the great application prospect of UAV photogrammetry technology in the quantitative study of active tectonics.

The 3 August 2014 Ludian, Yunnan M_S6.5 earthquake has spawned more than 1, 000 landslides which are from several tens to several millions and over ten millions of cubic meters in volumes. Among them, the Hongshiya and Ganjiazai landslides are the biggest two with volumes over 1 000×10⁴m³. The Hongshiya and Ganjiazai landslides are two typical landslides, the former belongs to tremendous rock avalanche, and the latter belongs to unconsolidated werthering deposit landslide developed in concave mountain slope. Based on field investigations, causes and formation mechanism of the two landslides are discussed in this study. The neotectonic movement in the area maintains sustainable uplifting violently all the time since Cenozoic. The landform process accompanied with the regional tectonic uplifting is the violent downward erosion along the Jinshajiang River and its tributary, forming landforms of high mountains and canyons, deeply cut valleys, with great height difference. The regional seismo-tectonics situation suggests that:Ludian earthquake region is situated on the southern frontier boundary of Daliangshan secondary active block, and is seismically the strongest active area with one earthquake of magnitude greater than M5.0 occurring every 6 years. Frequent and strong seismicity produces accumulated effects on the ground rock to gradually lower the mechanical strength of slopes and their stability, which is the basis condition to generate large-scale collapse and landslide at Hongshiyan and Ganjiazhai. The occurring of Hongshiyan special large rock avalanche is associated with the large terrain height difference, steep slope, soft interlayer structure and unloading fissures and high-angle joints. The formation mechanism of Hongshiyan rock avalanche may have three stages as follows:Stage 1, when P wave arriving, under the situation of free surface, rocks shake violently, the pre-existent joints(in red)parallel to and normal to the river and unloading cracks are opened and connected. Stage 2, on the basis of the first stage, when S wave arriving, the ground movement aggravates. Joints(in green)along beds develop further, resulting in rock masses intersecting each other. Stage 3, rock masses lose stability, sliding downward, collapsing, and moving over a short distance along the sliding surface to the inside of the valley, blocking the river to form the dammed lake. The special large landslide at Ganjiazhai is a weathering layer landslide occurring in the middle-lower of a large concave slope. Its formation process may have two stages as follows:Firstly, under strong ground shaking and gravity, the ground rock-soil body around moves and assembles to the lower of the central axis of the large concave slope, which suffers the largest earthquake inertia force and firstly yields plastic damage to generate compression-expansion deformation, because of the largest water content and volume-weight within the loose soil of it. Secondly, in view of the steep slope, along with the compression, the plastic deformation area enlarges further in the lower of slope, giving rise to a tensional stress area along the middle of the slope. As soon as the tensional stress exceeds the tensile strength of the weathering layer, a tensional fracture will occur and the landslide rolls away immediately making use of momentum. This two large landslides are the basic typical ones triggered by the M_S6.5 Ludian earthquake, and their causes and mechanism have a certain popular implication for the landslides occurring in this earthquake region.

Qilian Shan and Hexi Corridor, located in the north of Tibetan plateau, are the margin of Tibetan plateau's tectonic deformation and pushing. Its internal deformations and activities can greatly conserve the extension process and characteristics of the Plateau. The research of Qilian Shan and Hexi Corridor consequentially plays a significant role in understanding tectonic deformation mechanism of Tibetan plateau. The northern Yumushan Fault, located in the middle of the northern Qilian Shan thrust belt, is a significant component of Qilian Shan thrust belt which divides Yumushan and intramontane basins in Hexi Corridor. Carrying out the research of Yumushan Fault will help explain the kinematics characteristics of the northern Yumushan active fault and its response to the northeastward growth of the Tibetan plateau.Because of limited technology conditions of the time, different research emphases and some other reasons, previous research results differ dramatically. This paper summarizes the last 20 years researches from the perspectives of fault slip rates, paleao-earthquake characteristics and tectonic deformation. Using aerial-photo morphological analysis, field investigation, optical simulated luminescence(OSL)dating of alluvial surfaces and topographic profiles, we calculate the vertical slip rate and strike-slip rate at the typical site in the northern Yumushan Fault, which is(0.55±0.15)mm/a and(0.95±0.11), respectively. On the controversial problems, namely "the Luotuo(Camel)city scarp" and the 180 A.D. Biaoshi earthquake, we use aerial-photo analysis, particular field investigation and typical profile dating. We concluded that "Luotuo city scarp" is the ruin of ancient diversion works rather than the fault scarp of the 180 A.D. Biaoshi earthquake. Combining the topographic profiles of the mountain range with fault characteristics, we believe Yumu Shan is a part of Qilian Shan. The uplift of Yumu Shan is the result of Qilian Shan and Yumu Shan itself pushing northwards. Topographic profile along the crest of the Yumu Shan illustrates the decrease from its center to the tips, which is similar to the vertical slip rates and the height of fault scarp. These show that Yumu Shan is controlled by fault extension and grows laterally and vertically. At present, fault activities are still concentrated near the north foot of Yumu Shan, and the mountain ranges continue to rise since late Cenozoic.

There are evident neotectonic characteristics along the Dayingjiang Fault,with fault landforms developed,such as fault facet,linear ridges,fault troughs etc. ,and clear linear features in satellite images.The Quaternary Basins of Lianghe,Yingjiang,Sanggang and Xipahe are obviously controlled by the fault.Based on field investigation results at home and abroad in recent years,the fault has displaced the Late Pleistocene or Holocene strata,as revealed by the outcrops at Dapingzi,Binghui,Laoxinzhai and Guangyun.At Binghui village,the age of the displaced stratum is(56.56±4.81)ka BP,and on the fault plane,loosely consolidated gouge is developed.The ages of the displaced strata at Laoxinzhai village are(24.80±2.11)ka BP and(28.80±2.45)ka BP.At Xipahe of Myanmar,there is a fault trench developed on T₂ terrace,with 500m in length,12～16m in width and 5～8m in depth,and the terrace formation age is(10.13±0.86)ka BP.It means that the latest active time of Dayingjiang Fault is late-Pleistocene to Holocene,and the fault has been dominated by left-lateral slip,with an average left-slip rate of 1.5～2.5mm/a along the northeastern segment and 1.2～1.6mm/a along the southwestern segment.