The accumulation of luminescence signals in mineral crystals correlates with the duration of exposure to radiation. This phenomenon has been utilized as a tool for measuring sediment age and has found extensive application in various research endeavors. While quartz and feldspar luminescence signals have been utilized for dating in recent years, their effectiveness is constrained by early saturation, limiting their dating range to less than 300ka. In contrast, calcite exhibits high sensitivity to dose responses of thermoluminescence signals and possesses a characteristic saturation dose that can reach levels of 3 000-5 000Gy, making it a promising material for thermoluminescence dating. This has the potential to extend the age range of luminescence dating to the Quaternary period and broaden the application scope of low-temperature thermochronology. Providing quantitative descriptions of bedrock exhumation history through low-temperature thermochronology can offer crucial data support for understanding the interconnected relationship between tectonic activity, climate influences, and geomorphic evolution. Low-temperature thermoluminescence thermochronology, characterized by its high resolution and low closure temperature, presents advantages over commonly used apatite U-Th/He thermochronology in elucidating the excavation history of the Earth’s crust surface(approximately 1~2km). However, traditional minerals utilized for reconstructing bedrock cooling history, such as quartz and feldspar, exhibit rapid saturation, limiting the study period to less than 200ka. In contrast, calcite boasts an exceptionally high characteristic saturation dose and lower dose rate, making it a promising new dating mineral that extends the upper limit of low-temperature thermoluminescence thermochronology beyond 0.5Ma.

This paper begins by introducing the principle and application of thermoluminescence dating, followed by an overview of commonly used techniques for measuring dose rate and equivalent dose. The thermoluminescence dating process primarily involves equivalent dose measurement and dose rate measurement. Considerable research has been conducted on equivalent dose, and newly developed methods such as single aliquot regenerative dose, multiple aliquot regenerative dose, and multiple aliquot-additive dose have addressed issues related to sensitivity changes caused by heating, thereby enhancing the accuracy of dating results. Additionally, the paper summarizes recent advancements in calcite thermoluminescence dating and kinetic parameters. To validate the method, we performed thermoluminescence dating analysis on calcite grains in bedrock samples collected from the Tiger Leap Gorge of the Jinsha river.

After passing through Shigu, the Jinsha river experiences a sudden change in flow direction, carving its way through the Yulong-Haba mountain range to create the renowned “Tiger Leaping Gorge.” This geographic feature is characterized by active tectonics and intense river erosion, making it an ideal site for investigating the interplay among tectonics, climate, and surface processes. However, the Tiger Leaping Gorge primarily comprises limestone and griotte, lacking minerals such as apatite and zircon necessary for traditional low-temperature thermochronology dating(only exposed in the Upper Tiger Leaping Gorge). Consequently, it presents an ideal setting for exploring calcite low-temperature thermoluminescence thermochronology. SAR-ITL can detect the 280℃ thermoluminescence peak signal of calcite at 235℃, effectively mitigating the influence of spurious thermoluminescence. Moreover, the number of calcite grains required is lower than that of the MAAD test. The findings highlight the potential of this method for estimating the exhumation rate of carbonate rock. To facilitate its more effective utilization in the field of tectonic geomorphology, we address the challenges and potential applications of calcite thermoluminescence dating.

An M_S7.4 earthquake occurred in Madoi County, Guoluo Tibetan Autonomous Prefecture, Qinghai Province of China at 02:04 (Beijing Time) on May 22, 2021. A total of seven 800~3 000m trans-fault survey lines were targeted laid along different parts of the seismic surface rupture zone(the west, mid-west, mid-east, and the east), one month after the earthquake when the detailed field investigation of the coseismic displacement and the spread of the seismic surface rupture zone had been carried out. The soil gases were collected and the concentrations of Rn, H₂, Hg, and CO₂ were measured in situ.
The results show that the maximum value of Rn, H₂, Hg and CO₂ concentrations in different fracture sections of the surface rupture was 2.10~39.17kBq/m³(mean value: 14.15kBq/m³), 0.4×10^-6~720.4×10^-6(mean value: 24.93×10^-6), 4~169ng/m³(mean value: 30.72ng/m³)and 0.73%~4.04%(mean value: 0.59%), respectively. In general, the concentration of radon is low in the study area, which may be related to the thick overburden and the lithology dominated by sandstone. The concentration characteristics of hydrogen and mercury released from soil have good consistency, and the concentrations are higher at the east and west ends of the surface rupture zones but were lower in the middle of the rupture zone. This is consistent with the field investigation showing that the earthquake-induced surface rupture zone and deformation are more concentrated in the western section, while the eastern section has a large amount of seismic displacement.
The fault strikes at the east and west ends of the Madoi M_S7.4 earthquake surface rupture have deviated from the NW direction to a certain extent, and there also exits two branching faults and rupture complexities at the east end of the main fault of the Madoi earthquake. In the west end of the surface rupture, i.e., the south of Eling Lake, the fault strike turns to EW direction. We laid two survey lines(line 2 and line 3)at the west end of the rupture, the concentration of Rn, H₂ and Hg escaped from line 3 is the lowest one among all lines while the gas concentration of line 2 is significantly higher. In the vicinity of line 3, the field geological survey did not find the cracked and exposed surface rupture, and only a small number of liquefaction points were distributed near the Eling Lake. The soil gas concentrations and morphological characteristics were consistent with the field phenomena. At the east end of the rupture zone, the soil gas morphological characteristics of the south and north fault branches were inconsistent: the soil gas of the south branch showed a single-peak type which was more similar to that at the west end, but the gas concentration pattern of the north fault branch showed a multiple-peaks type. This phenomenon is consistent with the characteristic shown in the surface fracture mapping, that is, the deformation zone of the rupture where is wider.
To find out the source of soil gas and the possible influencing factors of soil gas concentrations in the study area, the carbon isotope and helium isotope of the collected gas samples were analyzed. The value of ³He/⁴He shows that the noble gas in the study area is mainly an atmospheric source, but the results of δ¹³C and CO₂/³He show that the soil gas along the surface rupture of the Madoi earthquake has the mixed characteristics of atmospheric components and crustal components, which to a certain extent reflects the cutting depth of main fault-Jiangcuo fault may be shallow, and it is speculated that the surface rupture caused by Madoi M_S7.4 earthquake may be confined to the shallow crust.

The collision of the Indian plate with Eurasia in the early Cenozoic era drove the emergence of the Tibetan plateau. At the same time, the subduction of the western Pacific plate towards Eurasia resulted in the stretching and thinning of the lithosphere in eastern Asia, leading to a series of faulted basins and marginal seas. The macro-geomorphic pattern of East Asia was finally established under the control of these two tectonic domains. In this case, the Yellow River, which originated from the Tibetan plateau and flowed through the Loess Plateau and the North China Plain, carried a huge amount of detrital material into the Bohai Sea, which played an important role in the regional geochemical cycle, environmental change, sedimentary flux and the diffusion of detrital material in the shelf sea. Therefore, tracing sediment sources in the Yellow River Basin is of great importance for understanding the coupling relationship between uplift and denudation in the northeastern Tibetan plateau, East Asian monsoon evolution, and detrital material accumulation. However, the Yellow River Basin spans multiple climatic and tectonic zones with different provenance areas, so it is particularly critical to select appropriate provenance tracing methods.

Although K-feldspar is more vulnerable to chemical weathering than zircon, it is a widely distributed rock forming mineral and can best represent the provenance characteristics of a certain area. The non-clay minerals in the Yellow River Basin are mainly composed of quartz and feldspar. At the same time, the Pb isotope ratios(²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb)of K-feldspar in different blocks are much different from those of Nd and Sr isotope systems and are often used to construct regional Pb isotope geochemistry province, continental crust evolution, and reconstruct paleocurrent direction, etc. In recent years, detrital K-feldspar Pb isotopic composition has been successfully used to trace the provenance of the Indus, Yangtze and Mississippi Rivers. But this method has not been carried out in the Yellow River Basin. Therefore, we systematically analyzed the detailed K-feldspar Pb isotopic compositions from the Yellow River Basin, and compared the results with the potential source areas to determine the specific source areas. It also can provide basic comparative data for future studies on the formation age of the Yellow River and material source areas of the Loess Plateau and deserts in the northwestern China.

We analyzed 15 samples from the Yellow River Basin and obtained 967 in-situ Pb isotopic results of K-feldspar grains by laser erosion inductively coupled plasma mass spectrometer(LA-MC-ICP-MS). K-feldspar grains in the samples from the Yellow River are angular, subangular and subcircular, with diameters ranging from 20μm to 300μm. The ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of K-feldspar grains from the source of the Yellow River to Lanzhou city range from 20 to 16 and 42 to 36. However, some ratios of ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb of K-feldspar grains from the Lanzhou city range from 23 to 19 and 40 to 37, respectively. The ²⁰⁶Pb/²⁰⁴Pb ratio of most K-feldspar samples in Bayannur city is greater than 19, and the maximum value is 24.79, while this ratio from Hequ and Hancheng cities located in the middle reaches of the Yellow River is less than 18.5. The ²⁰⁶Pb/²⁰⁴Pb ratios of the Mesozoic sandstone near the Hequ city range from 16 to 15. The ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of K-feldspar grains from the Weihe River, which is the largest tributary of the Yellow River, range from 19 to 17 and 40 to 37. The ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of K-feldspar grains in the Fenhe River, Yiluohe River, Kaifeng and Lijin cities range from 21 to 14 and 42 to 33. The comparison results of ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios show that the Pb isotopic compositions of K-feldspar grains in the upper Yellow River, Daxiahe River and Huangshui River are significantly different from those in the Lanzhou city. The Pb isotopic composition of K-feldspar grains from the Yellow River from the Lanzhou city is consistent with that in the Bayannur city, which is influenced by similar eolian provenance. K-feldspar grains from the Yellow River and Fen River in the Jinshan Gorge are mainly from the Loess Plateau. By contrast, the K-feldspar grains in the Weihe River are mainly derived from the Qinling Mountains. The Pb isotopic compositions of K-feldspar grains in the Kaifeng and Lijin cities of the lower Yellow River are different to those in the upper Yellow River and the North China Plate, but similar to those in the middle reaches of the Yellow River. The Loess Plateau plays a leading role in the source of K-feldspar gains in the middle and lower reaches of the Yellow River.

Coseismic surface rupture length is one of the critical parameters for estimating the moment magnitude based on the empirical relationships and later used in assessing the potential seismic risk of a region. On 22 May 2021, the M_W7.4 Madoi earthquake occurred in the northeastern part of the Tibetan plateau(Madoi County in Qinghai Province, China)and ruptured the poorly known Jiangcuo Fault along the extension line of the southeastern branch of the Kunlun Fault. We began our data acquisition using aerial photogrammetry by UAV three days after the earthquake. Between 24 May and 15 June 2021, more than 40000 high-resolution low-altitude aerial photos were acquired covering a total length of 180km along the surface rupture. Based on detailed field investigations, combined with a fine interpretation of sUAV-derived orthophotos and high-resolution DEMs, we determined a total length of~158km of the coseismic surface rupture extending to the eastern end at 99.270°E, which is basically consistent with the position given by previous geophysical methods. Although the extending segment is located beyond the end of the continuous surface rupture trace near Xuema Township, it should be included in the calculation of the length of the surface rupture as part of the tectonic surface rupture. The surface rupture is segmented into four sections, named from west to east: the Eling Lake, Yematan, Yellow River, Jiangcuo branch sections. Additionally, to the east of Dongcaoa’long Lake, we mapped semi-circular arc-shaped continuous tension-shear fractures in the dune area with a short gap(~3km)connecting to the east of the Jiangcuo branch. The surface ruptures along the southeastern Youyunxiang segment also sporadically appear in several sites, locally relatively continuous, covered by the sand dune with vertical displacements of up to 30cm. After passing through the dunes, the surface rupture of the Youyunxiang segment began to spread widely, extending continuously with a strike of nearly east-west. However, it should be noted that the rupture lengths of the Youyunxiang segment and other branches are not counted in the total earthquake rupture length. By comparing the current research results, we believe that the critical factors causing the significant differences of the measured length of coseismic surface ruptures would depend on: 1)more extensive and detailed field investigations combined with a fine interpretation of high-resolution images; 2)avoidance of repeated calculation of superimposed sections on both sides of the complex geometrical area. In this study, combined with the fine interpretation of high-precision image data, many surface rupture traces in the dunes of the Youyunxiang segment were identified(verified and confirmed by field inspection)and more continuous surface rupture segments on the F1 fault, which is difficult to reach by human beings, were discovered, also highlights the important role of digital photogrammetry in the study of active tectonics. The studies of the strong historical earthquakes around the Bayan Har block show that the coseismic surface rupture length is larger than that estimated by the empirical relationships. Further research thus is highly necessary to uncover its mechanism and indicative significance.

Exact characteristics of surface rupture zone are essential for exploring the mechanism of large earthquakes. Although the traditional field surface rupture investigation methods can obtain high-precision geomorphic data in a local area, it is difficult to rapidly get an extensive range of high-precision topographic and geomorphic data of the entire fault due to its limited measurement range and low efficiency. In addition, manual measurement is of tremendous workload, high cost, time-consuming and laborious, and the subjective differences in the judgment standards during the manual operation process may also cause the measurement results to be inconsistent with the actual terrain characteristics. In recent years, the development of photogrammetry technology has provided another more effective technical means for the rapid acquisition of high-precision topographic and geomorphic data, which has dramatically changed the way of geological investigation, improved the efficiency of fieldwork. At the same time, it also makes it a reality to reproduce the 3D tectonic features of field tectonic deformation indoors.
Structure from Motion(SfM)multi-view mobile photogrammetry technology is widely concerned for its convenience, fast and low-cost acquisition of high-resolution 3D topographic data in a working area of tens-kilometers scale. The emergence of this method has greatly improved the automation degree of photogrammetry. The technology obtains image sets by motion cameras, uses a feature matching algorithm to extract homonym features from multiple images(at least three images), determines the relative positional relationship of cameras during photography, and continuously optimizes by the nonlinear least square algorithm. Finally, the pose of cameras is automatically solved, and 3D scene structure is reconstructed. The technology can restore the original 3D appearance of the object in the computer by a set of digital images with a certain degree of overlap. In the applications of terrain mapping, this technology only needs to combine a small number of ground control points(GCPs)to quickly establish digital orthophoto maps(DOMs)and digital elevation models(DEMs)with high-precision. In this way, low altitude remote sensing platforms such as small and medium-sized UAVs have provided a foundation for SfM photogrammetry technology.
After the Madoi M_W7.4 earthquake occurred on May 22, 2021, our research team rushed to the site as soon as possible and conducted the rapid photogrammetry of the entire coseismic surface rupture zone in a short period with the use of the CW-15 VTOL fixed-wing UAV. We completed the collection of topographic data in an area with ~180km length and ~256km² area and collected 34302 aerial photographs. We used Agisoft PhotoScan TM software to process the images and generate DOMs quickly. The DOM resolution of the entire surface rupture was 2~7cm/pix, most of which were 3~5cm/pix. Then we used GIS software to vectorize the surface rupture. The centimeter-scale high-resolution DOMs could clearly display the coseismic surface rupture’s spatial distribution and the relative width. On this basis, the surface rupture could be accurately interpreted, and related parameters such as coseismic offsets could be extracted. In this study, the horizontal offsets measured by orthophoto images were basically consistent with the field measurement results, which proved the authenticity and reliability of the data obtained by the UAV photogrammetry method.
In order to obtain more detailed surface rupture vertical offset data, we used DJI Phantom 4 Pro V2.0 UAV to collect terrain information of several areas with the most significant rupture deformation. The DEM resolution obtained could reach centimeter-scale, and the accuracy was greatly improved. The high-resolution topographic and geomorphic data obtained by this method could accurately identify tiny fault features, clearly display sub-meter-level vertical offset features, significantly improve the accuracy of offset measurement, and achieve high-resolution 3D reconstruction of fault geomorphic.
In addition, we selected typical surface ruptures in the field, such as compressional stepovers, tensional cracks, and pressure ridges, and collected their 3D structural features using the iPhone 12 Pro LiDAR scanner. The 3D Scanner application was used to optimize the image, completely restore the “real object” in 3D to realize the indoor reconstruction of the 3D structure of surface ruptures and pressure ridges. The augmented reality(AR)imaging models could truly reflect the characteristics and details of surface ruptures, forming the same effect as field observations. This technology, which creates 3D models of close-range environments without any prior preparation, provides a novel, economical, and time-saving method to rapidly scan morphological features of small and medium-sized landforms(from centimeters to hundreds of meters)at high spatial resolution. This is the fastest and most convenient way to collect 3D models in field geological investigation without using external equipment, which provides a new idea for future geological teaching and scientific research.
Although photogrammetry technology still has some limitations, such as the short flight time of the flight platform, being easily affected by factors such as weather and altitude, and unsatisfactory aerial photography in densely vegetated areas, it is believed that these problems will be solved with the advancement of technology. Once solved, photogrammetry will become an essential technical means in quantitative and refined research on active tectonics.

The coseismic displacements are required to characterize the earthquake rupture and provide basic data for exploring the faulting mechanism and assessing seismic risk in the future. Detailed field investigation is still an important way to acquire reliable coseismic displacements comparing to geodetic measurements. Combining with previous research on other earthquakes, this study tries to discuss distributed deformation along the strike rupture and its implications. The M_W7.4 Madoi earthquake ruptured the southeast section of the Kunlun Shankou-Jiangcuo Fault on May 22, 2021, in Qinghai Province. It is a typical strike slip event, and its epicenter locates at~70km south of the East Kunlun Fault, which is the north boundary of the Bayan Har block. Field investigation results show that the surface rupture extends along the piedmont. The deformation features mainly include compression humps, extensional and shear fissures, and scarps. After the earthquake, we used the unmanned aerial system to survey the rupture zone by capturing a swath of images along the strike. The swath is larger than 1km in width. Then we processed the aerial images by commercial software to build the orthoimage and the digital elevation model(DEM)with high resolutions of 3~5cm. We mapped the surface rupture in detail based on drone images and DEM along the western section. Meanwhile, we also got the commercial satellite images captured before the earthquake, on 2nd January 2021. The images were processed with geometrical rectification before comparison. The spatial resolution of satellite images before earthquake is about 0.5m.
At the south of the Eling Hu(Lake), the clear offset tire tracks provide an excellent marker for displacement measurement. We located the positions of tracks precisely based on remote sensing images, and compared between the tracks lines after earthquake and the corresponding positions before earthquake, then extracted distance difference, which is defined as coseismic displacements. The results show that the total displacement is about 3.6m, which contains the distributed deformation of about 0.9m. The off-fault deformation is about 33% of the on-fault and about 25% of the total deformation. The ratios are similar to previous studies on earthquake worldwide. The fault zone width is probable about 200m. The total horizontal displacement measured by this study is similar to the slip in depth by InSAR inversion, which implies that there is no slip deficit at the west rupture section of the earthquake.
The results also present the asymmetry of distributed deformation that most distributed deformation occurs at the south of the surface rupture zone. Comparing with other earthquakes in the world, it is likely that the asymmetrically distributed deformation is common in strike-slip earthquakes and the asymmetric feature is not related to the property of the material. The characteristics of distributed deformation might be related to fault geometry at depth or local stress state. More work is needed to resolve this question in the future. This study implies that we probably underestimated the slip rates resulting from ignoring distributed deformation in the past. In order to avoid underestimation of slip rates, we can correct the previous results by the ratio of distributed deformation to total slip. It is also suggested that the study sites should be on the segment with narrow deformation and simple geometry.

Detailed mapping of coseismic surface rupture can provide valuable information for understanding the geometrical complexities, dynamic rupture processes and fault mechanisms. Fault geometrical complexities, such as bends, branches, and stepovers are common in strike-slip fault systems and can control the coseismic surface rupture characteristics to a certain extent. Observational studies of surface ruptures in past earthquakes suggested that special rupture characteristics would form distributed ruptures and rupture gaps. The detailed mapping has become an important way to study the surface rupture. According to the China Earthquake Networks Center(CENC), the M_W7.4 earthquake occurred at 2:04 PM on May 22, 2021, in Madoi County, Qinghai Province. The epicenter is about 70km south of the eastern Kunlun Fault on the northern boundary of the Bayan Kera block. It is the largest earthquake that hit the Chinese mainland since the Wenchuan M_S8.0 earthquake in 2008. After field investigation and rupture mapping on the computer, Yao et al.(2022)estimated that the length of surface rupture of this earthquake is 158km. Surface ruptures of the M_W7.4 Madoi earthquake broke through the geometric discontinuities such as step-overs and bends, and formed various coseismic surface fractures, especially in the middle segment. In the survey of the Madoi earthquake, we rapidly acquired aerial image data using UAV aerial photogrammetry and obtained high-resolution digital orthograph models(DOMs)and digital elevation models(DEMs)using PhotoScan software based on the SfM algorithm processing. Those data provide an opportunity for detailed mapping of seismic rupture and also provide an important reference for fieldwork. Based on high-resolution topographic data, we carried out detailed surface rupture mapping, classification, geometric structure and strike analysis for the ~30km section of the epicenter segment. At the same time, we conducted field work to supplement and proofread the maps.
According to the characteristics of surface ruptures in the epicenter area, we divided the ruptures into six segments. The surface ruptures along segment S₁ and segment S₆ are concentrated near the main fault, while the surface ruptures in the stepover(segment S₃, S₄, and S₅)are distributed dispersively, and the secondary ruptures along the segment S₂ are also distributed scatteredly, with the main rupture missing. To reveal the distribution characteristics of surface fractures more clearly, the surface ruptures are divided into the main rupture, secondary rupture, surface rupture and collapse rupture, among which the genesis of the surface rupture is uncertain. There are a lot of typical tensile ruptures with left-lateral component in segment S₁, the strike of the ruptures is consistent with the strike of the main fault or intersects the main fault with a small angle. The maximum width of the main rupture in segment S₁ is ~50m. The main ruptures in segment S₆ are developed along with the preexisting tectonic topography and the offset of the left-lateral displaced gully is up to tens of meters in magnitude. The surface ruptures are distributed in an echelon pattern, and all intersected with the strike of the main fault at a large angle. The location and size of the step-over are determined according to the topography and rupture morphology of faults in segment S₁ and segment S₆. The surface ruptures on the floodplain and banks of the Yellow River are in various forms and difficult to classify accurately. Therefore, only the typical seismic ruptures developed along the accumulated tectonic topography are labeled as main ruptures, and other typical seismic ruptures inconsistent with the location of the main fault are labeled as secondary ruptures. The typically collapse ruptures distributed along the river bank or lake bank are labeled as collapse ruptures, while the rest are labeled as surface ruptures. Surface ruptures in segment S₃ are distributed on the planar graph, but they have a dominant strike in the NE direction that can be seen from the diagram map. In the floodplain of the Yellow River, there are typical “grid” cracks, “explosive” cracks, and tensile cracks, and many cracks are accompanied by sand liquefaction which is beadlike, single, and distributed along the cracks. After the earthquake, the geodesic and geophysical data obtained quickly from the InSAR co-seismic deformation map and precise positioning of aftershocks revealed the basic morphological characteristics of earthquake rupture and provided valuable information such as earthquake rupture length, which provided an important reference for the design of UAV aerial photography and fieldwork. Compared with the rupture trace in field investigation by Pan et al.(2021), the surface rupture coverage obtained by mapping based on UAV aerial photogrammetry technology in this study is more extensive and accurate.
In general, surface ruptures of the Madoi earthquake are widely distributed, and we have classified those ruptures into the main seismic ruptures, secondary seismic ruptures, collapse cracks, and other surface ruptures. In addition to the seismic rupture with the same strike, there are also a variety of distributed surface ruptures with different strikes from the main fault. In these distributed surface ruptures, there are also many surface ruptures whose cause is not clear and they may be affected by tectonics or strong quake. For example, the “grid” and “explosive” surface ruptures on the Yellow River floodplain may be related to the strong quake near the epicenter or may also be related to the three-dimensional dynamic ruptures process in the initial stage. In this study, the characteristics of earthquake surface rupture in the step-over and adjacent sections near the epicenter has been described in detail, which provides a deeper understanding of the distributed coseismic surface rupture in the strike-slip fault.

Earthquake surface ruptures are the key to understand deformation pattern of continental crust and rupture behavior of tectonic earthquake, and the criteria to directly define the active fault avoidance zone. Traditionally, surface fissures away from the main rupture fault are usually regarded as the result triggered by strong ground motion. In recent years, the earth observation technology of remote sensing with centimeter accuracy provides rich necessary data for fine features of co-seismic surface fractures and fissures. More and more earthquake researches, such as the 2019 M_W7.3 Ridgecrest earthquake, the 2016 M_W7 Kumamoto earthquake, the 2020 M_W6.5 Monte Cristo Range earthquake, suggest that we might miss off-fault fissures associated with tectonic interactions during the seismic rupture process, if they are simply attributed to effect of strong ground motion. Such distribution pattern of co-seismic surface displacement may not be isolated, it encourages us to examine the possible contribution of other similar events. The 22 May 2021 M_W7.4 Madoi earthquake in Qinghai Province, China ruptured the Jiangcuo Fault which is the extension line of the southeastern branch of the Kunlun Fault, and caused the collapse of the Yematan bridge and the Cangmahe bridge in Madoi County. The surface rupture in the 2021Madoi earthquake includes dominantly ~158km of left-lateral rupture, which provides an important chance for understanding the complex rupture system.
The high-resolution UAV images and field mapping provide valuable support to identify more detailed and tiny co-seismic surface deformation. New 3 to 7cm per pixel resolution images covering the major surface rupture zone were collected by two unmanned aerial vehicles (UAV) in the first months after the earthquake. We produced digital orthophoto maps (DOM), and digital elevation models (DEM) with the highest accuracy based on the Agisoft PhotoScan^TM and ArcGIS software. Thus, the appearance of post-earthquake surface displacement was hardly damaged by rain or animals, and well preserved in our UAV images, such as fractures with small displacement or faint fissures. These DOM and DEM data with centimeter resolution fastidiously detailed rich details of surface ruptures, which have been often easily overlooked or difficult to detect in the past or on low-resolution images. In addition, two large-scale dense field investigation data were gathered respectively the first and fifth months after the earthquake. Based on a lot of firsthand materials, a comprehensive dataset of surface features associated with co-seismic displacement was built, which includes four levels: main and secondary tectonic ruptures, delphic fissures, and beaded liquefaction belts or swath subsidence due to strong ground motion. Using our novel dataset, a complex distributed pattern presents along the fault guiding the 158km co-seismic surface ruptures along its strike-direction. The cumulative length of all surface ruptures reaches 310km. Surface ruptures of the M_W7.4 Madoi earthquake fully show the diversity of geometric discontinuities and geometric complexity of the Jiangcuo Fault. This is reflected in the four most conspicuous aspects: direction rotation, tail divarication, fault step, and sharp change of rupture widths.
We noticed that the rupture zone width changed sharply along with its strike or geometric complexity. Near the east of Yematan, on-fault ruptures are arranged in ten to several hundred meters. Besides clearly defined surface ruptures on the main fault, many fractures near the Dongo section and two rupture endpoints are mainly along secondary faulting crossing the main fault or its subparallel branches. Lengths of fracture zones along two Y-shaped branches at two endpoints are about 20km. At the rupture endpoints, the fractures away from the main rupture zone are about 5km. Some authors suggested the segment between the Dongcao along lake and Zadegongma was a “rupture gap”. In our field investigation, some faint fractures and fissures were locally observed in this segment, and these co-seismic displacement traces were also faintly visible on the UAV images.
It is also worth noting that near the epicenter, Dongo, and Huanghexiang, a certain amount of off-fault surface fissures appear locally with steady strike, good stretch, and en echelon pattern. Some fissures near meanders of the Yellow River, often appear with beaded liquefaction belts or swath subsidences. In cases like that, fissure strikes are, in the main, orthogonal to the river. Distribution pattern of these fissures is different from usual gravity fissures or collapses. But they can’t be identified as tectonic ruptures because clear displacement marks are always absent with off-fault fissures. Therefore, it is difficult to determine the mechanism of off-fault co-seismic surface fissures. Some research results suggested, that during the process of a strong earthquake, a sudden slip of the rupturing fault can trigger strain response of surrounding rocks or previous compliant faults, and result in triggering surface fractures or fissures.
Because of regional tectonic backgrounds, deep-seated physical environments, and site conditions(such as lithology and overburden thickness), the pattern and physicalcause of co-seismic surface ruptures vary based on different events. Focal mechanisms of the mainshock and most aftershocks indicate a near east-west striking fault with a slight dip-slip, but focal mechanisms of two M_S≥4.0 aftershocks show a thrust slip occurring near the east of the rupture zone. On the 1︰250000 regional geological map, the Jiangcuo Fault is oblique with the Madoi-Gande Fault and the Xizangdagou-Cangmahe Fault at wide angles, and with several branches near the epicenter and the west endpoint at small angles. Put together the surface fissure distribution pattern, source parameters of aftershocks and the regional geological map, we would like to suggest that besides triggered slip of several subparallel or oblique branches with the Jiangcuo Fault, inheritance faulting of pre-existing faults may promote the development of off-fault surface fissures of the 2021Madoi earthquake. Why there are many off-fault distributed surface fissures with patterns different from the gravity fissures still needs further investigation. The fine expression of the distributed surface fractures can contribute to fully understanding the mechanism of the seismic rupture process, and effectively address seismic resistance requirements of major construction projects in similar tectonic contexts in the world.

The elevation evolution history of the southeastern Tibet Plateau is of great significance for examining the deformation mechanism of the plateau boundary and understanding the interior geodynamic mechanics. It provides an important window to inspect the uplift and deformation processes of the Tibet Plateau, and also an important way to test two controversial dynamic end-element models of the Plateau boundary. In recent years, some breakthroughs have been made in the study of paleoaltitudes in the southeastern Tibet Plateau, which allows us to have a clearer understanding of its evolution process and dynamic mechanism. By reviewing and recalculation of the latest achievements of paleo-altitude studies of the basins in the southeastern Tibet Plateau from north to south, including the Nangqian Basin, Gongjue Basin, Mangkang Basin, Liming-Jianchuan-Lanping Basin, Eryuan Basin, Nuhe Basin and Chake-Xiaolongtan Basin, we discuss the surface elevation evolution framework of the Cenozoic geomorphology and dynamics in the southeastern Tibet Plateau. The results show as follows:
(1)There was an early Eocene-Oligocene quasi plateau with an altitude of at least 2.5km from the north to middle of the southeastern Tibet Plateau(north of Dali), while the surface elevation in the south(south of Dali to Yunnan-Guizhou Plateau)was relatively low, even close to sea level. Until Miocene, the north to middle of the southeastern Tibet Plateau reached the present altitude, while the southern part of the Tibet Plateau showed a differential surface uplift trend, which established the present geomorphologic pattern. But it cannot be completely ruled out that this trend was probably caused by the accuracy of the calculation results.
(2)The quantitative constraints on the uplift process of the southeastern Tibet Plateau during Cenozoic provide certain constraints for the dynamic mechanism of geomorphic evolution in the southeastern Tibet Plateau. The northern and central parts of the southeastern Tibet Plateau can be well explained by the plate extrusion model. In this model, the collision and convergence between India and Eurasia plate or Qiangtang block and Songpan-Ganzi block resulted in the shortening and thickening of the upper crust in the region, and making the early stage(early Eocene)surface uplift. Subsequently, due to delamination or the continuous convergence between the Qiangtang block and the Songpan-Ganzi block resulting in the shortening and thickening of the crust, the plateau continued to grow northward and rose to its present altitude around Miocene. In the Eocene, the area from the south of the southeastern Tibetan plateau to the Yunnan-Guizhou Plateau mainly showed a low altitude. It seems that it may be in the peripheral area not affected by the shortening and thickening of the upper crust during the early stage India-Eurasia plate collision or plate extrusion and escape. In addition, as proposed by the lower crustal channel flow model, the lower crust material made the low-relief upland surface extending thousands of kilometers in the region uplift gradually towards the southeast, which seems to explain the low elevation landform of the region in the early stage, but it could not explain the whole uplift process of the southeastern Tibet Plateau. Therefore, a single dynamic model may not be able to perfectly explain the Cenozoic complex uplift process of the southeastern Tibet Plateau, and its process may be controlled by various dynamic processes.
(3)According to the paleoaltitude reconstruction results, if most areas of the ancient southeastern Tibet Plateau, especially the area to the north of Jianchuan Basin, had been uplifted in a certain scale and became part of the early plateau in the early Cenozoic, and reached to the current surface altitude around Miocene, the widely rapid surface erosion in this area since Miocene probably would be a continuous lag response to the finished surface uplift process, and the lag time may correspond to the sequential response process of surface uplift, the decline of river erosion base level and the gradual enhancement of river erosion capacity. Therefore, it is not proper to regard the rapid denudation and rapid river undercutting as the starting time of plateau uplift, as proposed in the previous thermochronological study.

In this study, we described a 14km-long paleoearthquakes surface rupture across the salt flats of western Qaidam Basin, 10km south of the Xorkol segment of the central Altyn Tagh Fault, with satellite images interpretation and field investigation methods. The surface rupture strikes on average about N80°E sub-parallel to the main Altyn Tagh Fault, but is composed of several stepping segments with markedly different strike ranging from 68°N~87°E. The surface rupture is marked by pressure ridges, sub-fault strands, tension-gashes, pull-apart and faulted basins, likely caused by left-lateral strike-slip faulting. More than 30 pressure ridges can be distinguished with various rectangular, elliptical or elongated shapes. Most long axis of the ridges are oblique(90°N~140°E)to, but a few are nearly parallel to the surface rupture strike. The ridge sizes vary also, with heights from 1 to 15m, widths from several to 60m, and lengths from 10 to 100m. The overall size of these pressure ridges is similar to those found along the Altyn Tagh Fault, for instance, south of Pingding Shan or across Xorkol. Right-stepping 0.5~1m-deep gashes or sub-faults, with lengths from a few meters to several hundred meters, are distributed obliquely between ridges at an angle reaching 30°. The sub-faults are characterized with SE or NW facing 0.5~1m-high scarps. Several pull-apart and faulted basins are bounded by faults along the eastern part of the surface rupture. One large pull-apart basins are 6~7m deep and 400m wide. A faulted basin, 80m wide, 500m long and 3m deep, is bounded by 2 left-stepping left-lateral faults and 4 right-stepping normal faults. Two to three m-wide gashes are often seen on pressure ridges, and some ridges are left-laterally faulted and cut into several parts, probably owing to the occurrence of repetitive earthquakes. The OSL dating indicates that the most recent rupture might occur during Holocene.
    Southwestwards the rupture trace disappears a few hundred meters north of a south dipping thrust scarp bounding uplifted and folded Plio-Quaternary sediments to the south. Thrust scarps can be followed southwestward for another 12km and suggest a connection with the south Pingding Shan Fault, a left-lateral splay of the main Altyn Tagh Fault. To the northeast the rupture trace progressively veers to the east and is seen cross-cutting the bajada south of Datonggou Nanshan and merging with active thrusts clearly outlined by south facing cumulative scarps across the fans. The geometry of this strike-slip fault trace and the clear young seismic geomorphology typifies the present and tectonically active link between left-lateral strike-slip faulting and thrusting along the eastern termination of the Altyn Tagh Fault, a process responsible for the growth of the Tibetan plateau at its northeastern margin. The discrete relation between thrusting and strike-slip faulting suggests discontinuous transfer of strain from strike-slip faulting to thrusting and thus stepwise northeastward slip-rate decrease along the Altyn Tagh Fault after each strike-slip/thrust junction.

The generation, abandonment and preservation of terraces formed in active tectonic areas are important to the analysis of the role of the tectonics and climate along the temporal variations, so it appears significant as how to use the effective quantitative methods to extract and accurately depict these terraces. The increasingly convenient acquisition of high-precision topographic data has greatly promoted the advancement of quantitative research in geoscience, making it possible to analyze mid-micro-geomorphic features on a large scale, especially by studying the temporal and spatial evolution of tectonic deformation through accurate capture of micro-geomorphic features. Over the past decade, the rapid development of LiDAR(Light Detection and Ranging)technology has provided unprecedented opportunity to access high-precision topographic data(up to centimeter in vertical and horizontal directions). However, its relatively high cost and relatively complex data processing techniques limit its widespread application in the field of earth sciences. In recent years, with the continuous innovation and advancement of topographic measurement technology, the three-dimensional structure of motion reconstruction technology(Structure from Motion, SfM)has gradually been introduced into the field of digital topographic photogrammetry due to its rapid advantage in providing quick, convenient and cost-effective methods for obtaining high-density geospatial point data. This method thus shows great potential for providing high resolution topographic data with comparable resolution and precision. Therefore, with the acquisition of more and more high-resolution terrain data in recent years, it is an important development trend to explore automated or semi-automated quantitative geomorphological analysis methods. R language, as an excellent programming language, has not been used in the geology and geomorphology, although is widely applied in medicine and meteorology based on its powerful capability of statistician and graphic visualization. In this paper, we focus on the Yellow River multi-terraces formed to the east of the Mijia Shan, which belongs to the Jingtai-Hasi Shan segment of the Haiyuan Fault. With the analysis and visualization of the high-resolution topographic data collected from the SfM in the environment of the R language, we implement the semiautomatic classification and mapping of the Yellow River multi-terraces. The method identifies 20 terraces with different elevation. Our results also imply that the younger terraces have better continuity and elongation, and the older terraces have more deformation, which can be demonstrated from their gradually notable semi-parabolic shape. Besides this, it also suggests the diverse evolution stages of the Yellow River terraces. Our study indicates that R language is expected to become an efficient tool of statistics and visualization of the high-resolution topographic data.