At 1:45 on January 8, 2022, a M_S6.9 earthquake occurred in Menyuan County, Haibei Prefecture, Qinghai Province. The epicenter(37.77°N, 101.26°E)is located in the western segment of the Lenglongling Fault of the Qilian-Haiyuan fault zone, with a focal depth of 10km. The earthquake is located in the northwest of the M_S6.4 Menyuan earthquake on January 21, 2016. According to the survey results of China Earthquake Administration, the highest intensity of this earthquake is IX degree, and the long axis of the isoseismic line is NWW-striking. The earthquake caused serious damage to the Daliang Tunnel between Haomen Station and Junmachang Station, and the Lanxin high-speed railway was interrupted. After the earthquake, the distribution of the earthquake surface rupture zone was quickly determined by interpreting the GF-7 satellite post-earthquake images, and the field surface rupture investigation was carried out at the epicenter site in the first time. The field investigation mainly includes the identification of surface rupture zones, the investigation of rupture characteristics, the survey of fault geomorphology, the high-precision aerial photogrammetry of typical rupture points, the identification and measurement of coseismic dislocation, and the investigation of earthquake disasters. Aerial photogrammetry realizes real-time difference through UAV linked network RTK, and takes high-definition photos from multiple angles. Pix4D software is used to complete calculation and point cloud encryption, etc. DSM (Digital Surface Model) and DOM (Digital Orthophoto Map) are generated for surface rupture space reproduction and feature measurement and analysis. According to the interpretation of high-resolution remote sensing images by GF-7 satellite and field investigation, the surface rupture of M_S6.9 Menyuan earthquake can be divided into NW-striking western segment of Lenglongling Fault and EW-striking eastern segment of Tuolaishan Fault. The two surface ruptures are 291° and 86.9°, respectively, and their lengths are not less than 26km and 3.5km respectively. We made detailed observation and measurement on the Jingyangling site, Daogou site, east Daogou site, Shixiamen site, the seven sites along the Liuhuanggou on the Lenglongling Fault, and the Yangchangzigou site on the Tuolaishan Fault. The surface rupture zone is mainly a complex coseismic surface deformation zone formed by the combination of multiple types of fractures, such as tensional fracture, tensional shear fracture, compression bulge and seismic depression, and characterized by sinistral strike-slip motion and partly by thrusting. Generally, the NW-striking ruptures exhibit left-lateral strike-slip characteristics, while NW-striking branch ruptures exhibit a small amount of right-lateral strike-slip characteristics. At Shixiamen site, four pasture fences were continuously offset left-laterally by 2.0~2.15m. At the Daliang Tunel site, the rut was offset left-laterally by 2.77m measured by UAV, which is the largest co-seismic left-lateral displacement of this earthquake. Based on high-resolution remote sensing image interpretation, field investigation, InSAR inversion of focal mechanism, fault rupture model and small earthquake precision location, it is determined that the earthquake occurred at the deep intersection of the Tuolaishan Fault and Lenglongling Fault, and the main seismogenic structure is the western segment of Lenglongling Fault(strike 112°, dip 88°). The Tuolaishan Fault on its west side ruptured simultaneously at the east end. According to the distribution characteristics of the surface ruptures and the field investigation of this earthquake, we believe that the Lenglongling Fault continues to extend westward after passing through the Liuhuanggou No. 1 site until the Jingyangling site, and the NWW-striking Lenglongling Fault has a “Y”-shaped contact relationship with the EW-striking Tuolaishan Fault. The 1986 M_S6.4 earthquake occurred at the northwestern end of the Lenglongling North Fault, which protrudes in an arc toward NE, and the 2016 M_S6.4 earthquake occurred at the southeastern end of the fault. Affected by the left-lateral strike-slip movement of the Lenglongling Fault, the small block bounded by the Lenglongling Fault and the Lenglongling North Fault also moves in the direction of SEE relative to the northern block. Therefore, the 1986 M_S6.4 earthquake showed tensile properties, and the 2016 M_S6.4 earthquake showed compression properties. The seismogenic structure of the Menyuan M_S6.9 earthquake is the Lenglongling Fault, so the earthquake is mainly characterized by left-lateral strike-slip. The M_S6.4 earthquake in 1986, M_S6.4 earthquake in 2016 and M_S6.9 earthquake in 2022all occurred in the western section of Lenglongling Fault. Three strong earthquakes of M>6 occurred in a short period of time, indicating that this area is still an accumulation area of stress and deformation, and has the potential risk of large earthquakes.
Due to the limitation of the data range of the Gaofen-7 satellite image and the inconvenience of traffic caused by the icing of the river, the location of the easternmost end point of the rupture and the exact length of the rupture have not been determined in this field investigation. We hope that follow-up studies will be carried out to confirm the rupture length when weather conditions are appropriate.

On April 20,2013,a strong earthquake of M_S 7.0 struck the Lushan County,Sichuan Province of China. In this paper,basic information of the April 20,2013 Lushan earthquake,historical earthquakes in the Lushan earthquake struck area and associated historical earthquake-triggered landslides were introduced firstly. We delineated the probable spatial distribution boundary of landslides triggered by the Lushan earthquake based on correlations between the 2008 Wenchuan earthquake-triggered landslides and associated peak ground acceleration(PGA).According to earthquake-triggered landslides classification principles,landslides triggered by the earthquake are divided into three main categories: disrupted landslides,coherent landslides,and flow landslides. The first main category includes five types: rock falls,disrupted rock slides,rock avalanches,soil falls,and disrupted soil slides. The second main category includes two types of soil slumps and slow earth flows. The type of flow landslides is mainly rapid flow slides. Three disrupted landslides,including rock falls,disrupted rock slides,and soil falls are the most common types of landslides triggered by the earthquake. We preliminary mapped 3883 landslides based on available high-resolution aerial photographs taken soon after the earthquake. In addition,the effect of aftershocks on the landslides,comparisons of landslides triggered by the Lushan earthquake with landslides triggered by other earthquake events,and guidance for subsequent landslides detailed interpretation based on high-resolution remote sensing images were discussed respectively. In conclusion,based on quick field investigations to the Lushan earthquake,the classifications,morphology of source area,motion and accumulation area of many earthquake-triggered landslides were recorded before the landslide might be reconstructed by human factors,aftershocks,and rainfall etc. It has important significance to earthquake-triggered landslide hazard mitigation in earthquake struck area and the scientific research of subsequent landslides related to the Lushan earthquake.

Wulanwulahu-Yushu Fault is an important active fault at the boundary area between Bayankala block and Qiangtang block.The slip rate of this fault in the late Quaternary is of fundamental importance for analyzing the seismic hazards and kinematic characteristics of neighboring active blocks.Due to the limited field conditions,the study of the late Quaternary fault activity on the eastern segment of this fault is rare.On the basis of interpretations of remote sensing images and field investigation,the eastern segment of this fault is active since late Quaternary and the offset geomorphic features are prominent,displaying left-lateral and high-angle thrust faulting.Using the methods of detailed geomorphic mapping,geological survey,differential GPS survey,optically stimulated luminescence(OSL)dating and radiocarbon(¹⁴C)dating,this paper makes an analysis of the late Quaternary geomorphic features and slip rate of the eastern segment of this fault.Four typical sites on the fault,including Xiabatang,Zhada,Shangbatang and southwest corner of Batang Basin,were selected for the field investigation.At Xiabatang,the vertical slip rate of the fault is 0.23～0.28mm/a since around 22～27ka BP,0.40～0.51mm/a since 4～5ka BP,and left lateral slip rate is 6.0mm/a since 27ka BP.At Zhada,the vertical slip rate is 0.23mm/a since around 24ka BP.At Shangbatang,the vertical slip rate is 0.45～0.63mm/a since around 6～9ka BP.At southwest corner of Batang Basin,the left lateral slip rate is 4.0mm/a since 150ka BP.The average vertical slip rate of the eastern segment of Wulanwulahu-Yushu Fault is 0.23～0.28mm/a since late Pleistocene,the average vertical slip rate is 0.40～0.63mm/a since early-mid Holocene,and the left lateral slip rate is about 4～6mm/a since late Quaternary.

Lots of different ideas stay on whether the Dongbeiwang-Xiaotangshan Fault in the northwest of Beijing exists or how it displays and acts.This paper analyzes the present seismic prospecting data and drill logs from exploration of active faults in Beijing urban areas,and reaches conclusion that the Dongbeiwang-Xiaotangshan Fault does exist as a subsurface fault and it is 40km long,trending NNE.Divided by the Nankou-Sunhe Fault,we name its northeast segment as the Xiaotangshan Fault and the southwest segment as the Dongbeiwang Fault.The Xiaotangshan Fault is active in early Pleistocene but not in middle Pleistocene.The Dongbeiwang Fault is active in the end of mid-Pleistocene but not in late Pleistocene.

Identification of potential seismic zone follows the earthquake structure analogy and seismic activity repetition principles at present.Active fault segmentation is an important aspect and should be considered when identifying potential seismic zones.There are three different segmentation plans along Daqingshan piedmont fault,Inner Mongolia.This article compares and analyses the segmentations and then gets a new potential seismic zone identification plan along Daqingshan piedmont fault.Identification of potential seismic zone includes the range subdivision and the estimation on the maximum earthquake magnitude of potential seismic zones.This article sub-divides the ranges of potential seismic zones according to active fault segmentation plan along the Daqinshan piedmont fault proposed by Ran Yong-kang.Ordos Massif is surrounded by depression zones which have similar earthquake structures and historical earthquake records with magnitude over 8 expect the Hu-Bao depression zone.So,this paper compares Daqingshan piedmont fault with other depression zones around Ordos Massif,especially the Huashan piedmont fault,and gets the conclusion of the maximum earthquake magnitude of Daqingshan potential seismic zones.