River terraces constitute key geomorphic units that record regional tectonic activity, fluvial incision, and Quaternary climate change. Previous studies have generally linked terrace formation to climatic fluctuations; however, such interpretations are largely based on indirect correlations between terrace chronologies and regional paleoclimate records, with limited direct climatic evidence derived from the terrace sediments themselves. This study investigates sediments from six terrace levels of the Qingyi River, developed over the past ~300 ka in the Longmen Shan region on the eastern margin of the Tibetan Plateau. Integrated analyses of pollen assemblages and trace element geochemistry were performed to reconstruct the climatic conditions during terrace formation and their sedimentary responses. The results indicate that pollen assemblages from different terrace levels clearly reflect cold–dry and warm–humid climatic conditions and correspond well with glacial–interglacial cycles, demonstrating that terrace sediments preserve direct paleoclimatic signals. Moreover, trace element compositions of the terrace sediments are primarily controlled by climatic conditions at the time of deposition and are only weakly influenced by post-depositional weathering. In particular, rare earth elements are relatively enriched in interglacial deposits and depleted in glacial deposits. These findings suggest that river terraces in the eastern margin of the Tibetan Plateau and adjacent mountainous regions are not formed during a single climatic stage. Instead, terrace formation can occur during transitions between glacial and interglacial periods. Importantly, terrace sediments preserve identifiable pollen and geochemical signatures corresponding to both glacial and interglacial conditions. This study provides direct sedimentological and paleoenvironmental evidence for understanding the mechanisms of climate-controlled river terrace formation and offers new perspectives for reconstructing Quaternary climate and geomorphic evolution in plateau-margin regions using terrace sediment records.

River terraces are essential objects for studying Quaternary landforms and active tectonics. Previous researchers often identified river terraces formed in different eras by height and landmark strata. However, terraces are usually scattered in regions with severe erosion, making comparing terraces of the same level challenging. Some sedimentary analyses, including abrasion of gravels, hardness of gravels, and weathering rind thickness, have been applied to compare terraces but proved limited and not quantitative. In this study, we interpreted and surveyed the terraces of the Qingyi River, which runs through the Longmen Shan Mountain in the eastern edge of the Tibetan Plateau. A systematic approach was presented to quantitatively compare river terraces in regions of high precipitation and erosion. Firstly, we summarized the interfering factors on sedimentation, the method of collecting samples, and the choice of testing materials. Secondly, weathering indicators derived from major element testing were applied to compare terraces of different ages. Finally, we concluded the relationship between weathering degree, the terrace age, and the terrace height. The results indicated that, within the terrace age range of 300 ka, the sediments in the terrace of the Qingyi river show a linearly increasing weathering trend. It proved that the degree of chemical weathering indicated by major elements can be well applied to studying river terraces and reflect the weathering differences between terraces of different ages, solving the problem of quantitative terrace comparison. Moreover, by combining the analysis of paleoclimate data, we reconstructed the weathering mechanisms of the terraces, which are controlled by the alternation between glacial and interglacial stages.

On 1 June 2022, a magnitude 6.1 earthquake struck the southern segment of the Longmenshan fault zone on the eastern edge of the Tibetan Plateau, once again causing casualties and economic losses. Understanding the deep-seated dynamic mechanisms that lead to seismic events in the Lushan earthquake area and assessing the potential hazards in seismic gap areas are of significant importance. In this study, we utilized 118 magnetotelluric datasets collected from the Lushan earthquake area and employed three-dimensional electromagnetic inversion with topographic considerations to characterize the deep-seated three-dimensional resistivity structure of the Lushan earthquake area. The results reveal that the Shuangshi–Dachuan fault in the Lushan earthquake area can be divided into two relatively low-resistivity zones: a western zone dipping southeastward and an eastern zone with a steeper slightly northwestern dip. These two zones intersect at a depth of approximately 20 km, forming an extensional pattern resembling a “Y” shape. The epicenters of both the 2013 and 2022 Lushan earthquakes are primarily located in the upper constricted portion of the pocket-like low-resistivity body at depth. The distribution of seismic aftershocks is confined within the region enclosed by the high-resistivity body, following the pattern of the Y-shaped low-resistivity zone.

The northwest Yunnan rift zone develops along the western boundary of the Sichuan-Yunnan block. The N-S trending eastern foothill fault of Yulong Snow Mountain on the northern edge of the rift zone extends between the Yulong Snow Mountain and the Lijiang Basin. It is the innermost part of the western boundary of the Sichuan-Yunnan block. The formation mechanism and activity characteristics of the eastern foothill fault of Yulong Snow Mountain are not only related to the complex structural boundary issues on the western side of Sichuan and Yunnan, but also can explain the uplift process of the Yulong Mountain and the Haba Mountain. After the MS7.0 earthquake in Lijiang in 1996, the eastern foothill fault of Yulong Snow Mountain widely attracted attention. However, previous research results about the Late Quaternary activity of this fault were diverse, including normal faulting, strike-slip faulting, and thrusting. It indicates that although this fault is only 60 kilometers long, it belongs to a complex tectonic system. Understanding the activity characteristics and earthquake-generating behavior of this fault is of great significance for establishing a complex structural model in the western Sichuan-Yunnan block. This article summarizes previous research data, reinterprets the fault based on satellite images, analyzes the typical fault-related landforms and identifies clear evidence of a combination of normal faulting and sinistral strike-slip along the fault. Field investigations have further validated these interpretations. Based on the conclusions and analysis presented in this paper, we have summarized different regional tectonic models corresponding to the different activity properties of eastern foothill fault of Yulong Snow Mountain. Meanwhile, from the perspective of plateau expansion, it is believed that the complex fault combination in the western Sichuan-Yunnan block is new and is forming a new western boundary of the Sichuan-Yunnan block.

Identifying seismic CH4 anomalies via remote sensing has been verified as a legitimate method. However, there are still some problems, such as unknown reliability due to the complex characteristics of seismic anomalies. In this study, a multi-dimensional and multi-scale methane seismic anomaly extraction process for remote sensing was constructed with the Robust Satellite Technique (RST) based on the Atmospheric Infrared Sounder (AIRS) CH4 data and then applied to the 2023 Türkiye–Syria earthquake. This study obtained the two-dimensional temporal–spatial distribution of methane anomalies and temporal variation in the anomaly index. Based on this, the three-dimensional profile structure of the 8-day methane anomaly was extracted to determine the reliability of the anomaly. Finally, based on the daily methane anomaly, combined with atmospheric circulation and backward trajectory analysis as auxiliary tools, the influence of air mass migration was excluded to enhance the accuracy of CH4 anomaly determination. The results show that the three-dimensional anomalous structure is consistent with the geological characteristics of tectonic activities, and it appears as a “pyramid” or “inverted pyramid” type in a three-dimensional space. The anomalies caused by air mass migration can be eliminated by combining them with synoptic-scale circulation motion. The time series calculated at the epicenter or a certain point in a region may not accurately reflect the influence of regional or specific tectonic activity in the atmosphere. Thus, the optimal determination of the range and magnitude of atmospheric anomalies caused by tectonic activities is a difficult task for future research.

The Lijiang–Jinpingshan fault (LJF) is an important secondary boundary fault that obliquely cuts the Sichuan–Yunnan rhombic block. It is of great significance for understanding the tectonic evolution of the Sichuan–Yunnan rhombic block and even the southeastern margin of the Tibet Plateau. Based on a digital elevation model (DEM), this work combines ArcGIS with MATLAB script programs to extract geomorphic indices including slope, the relief degree of the land surface (RDLS), hypsometric integral (HI), and channel steepness index (ksn) of 593 sub–watersheds and strip terrain profiles around the LJF. By analyzing the spatial distribution characteristics of the geomorphic indices and combining the regional lithology and precipitation conditions, the spatial distribution of the geomorphic indices around the study area was analyzed to reveal the implications of the LJF’s activity. The results of this work indicate that (1) the distribution of geomorphic indices around the LJF may not be controlled by climate and lithological conditions, and the LJF is the dominant factor controlling the geomorphic evolution of the region. (2) The spatial distribution patterns of geomorphic indices and strip terrain profiles reveal that the vertical movement of the LJF resulted in a pronounced uplift on its northwest side, with tectonic activity gradually diminishing from northeast to southwest. Furthermore, based on the spatial distribution characteristics of these geomorphic indices, the activity intensity of the LJF can be categorized into four distinct segments: Jianchuan–Lijiang, Lijiang–Ninglang, Ninglang–Muli, and Muli–Shimian. (3) The activity of the LJF obtained from tectonic geomorphology is consistent with the conclusions obtained in previous geological and geodesic studies. This work provides evidence of the activity and segmentation of the LJF in tectonic geomorphology. The results provide insight for the discussion of tectonic deformation and earthquake disaster mechanisms in the southeastern margin of the Tibet Plateau.

活动断层上盘浅部的高应力异常通常被认为是强震前兆之一,而低应力一般认为不会发生地震是安全的.然而多个震例表明,低应力状态下的地震危险性具有多解性.为进一步探讨强震前的应力异常特征,本研究利用2008年汶川Ms8.0级地震和2013年芦山Ms7.0级地震前的地应力测量结果和地震活动性参数b值,在考虑深部应力对浅部应力影响强度的基础上,建立了浅部应力对深部应力的响应模式,并对强震发生前不同的应力状态与地震危险性的关系进行了讨论.结果表明:活动断层上盘低b值对应浅部高地应力为潜在地震危险区,而对应低地应力则为地震危险性不确定区,需要借助更多的手段进一步确定;2008年汶川Ms8.0级地震前的低应力状态可能反映了区域应力存在较强的调整.本研究对运用断层浅部应力状态评估断层地震危险性具有一定的启示意义.

移动摄影测量技术SfM(Structure from Motion)的发展使活动构造研究中快速获得野外中小区域内高精度DEM数据更便捷,DEM数据精度是目前活动构造与测量领域较关注的问题.本文通过对比非RTK模式无人机摄影测量并结合地面控制点(GCPs)生成的SfM DEM数据与基于RTK移动摄影测量技术获取的RTK-SfM DEM数据差异,重点分析搭载RTK模块的移动摄影测量技术获取的DEM数据在垂向上的精度.数据采集、处理与对比结果表明:在添加地面控制点后的非RTK模式无人机摄影测量生成的DEM数据中,除测量区域边缘照片较少而产生畸变外,大部分地区畸变率较小;基于移动RTK技术摄影测量获取的高程数据畸变率更小,且与非RTK模式无人机摄影结合地面控制点生成的高程数据存在约0.85 m的系统高程误差,减去该误差后,点云对比结果表明二者95％以上的点垂向误差均＜0.05 m;搭载RTK模块的移动摄影测量技术获取的DEM数据在垂向上具有更高的精度,且节省了时间与人工成本.

In the Longmenshan thrust belt, the Dayi seismic gap, an area with few earthquakes, is located between the ruptures of the 2008 Wenchuan Earthquake and the 2013 Lushan Earthquake, with a length of approximately 40–60 km. To date, however, the extent of the seismic hazard of the Dayi seismic gap and whether this gap is under high stress are still hotly debated. To further evaluate the seismic hazard of the Dayi seismic gap with regard to stress, two boreholes (1,000 and 500 m deep) were arranged to carry out hydraulic fracturing in situ stress measurement on either side of the Shuangshi-Dachuan fault zone. This zone has a high seismic hazard and the capacity to undergo surface rupture Through the analogy of this new data with stability analysis using Byerlee’s Law and existing stress measurement data collected before strong earthquakes, the results show that the area surrounding the Shuangshi-Dachuan fault zone in the Dayi seismic gap (Dachuan Town) is in a state of high in situ stress, and has the conditions necessary for friction slip, with the potential hazard of moderate to strong earthquakes. Our results are the first to reveal the in situ stress profile at a depth of 1,000 m in the Dayi seismic gap, and provide new data for comprehensive evaluation of the seismic hazard in this seismic gap, which is of great significance to explore the mechanism of earthquake occurrence and to help mitigate future disaster.

龙门山断裂带大邑地震空区位于2008年汶川地震区和2013年芦山地震区之间,是一个长约40～60km缺少地震发生的区域.关于大邑地震空区的地震危险性以及是否存在高应力仍存在争议.为进一步从应力角度评估大邑地震空区的地震危险性,在具有发生地表破裂型地震能力并且具有高地震危险性的双石-大川断裂带两侧各布置1个钻孔（深度分别为1000和500m）进行水压致裂地应力测量工作.利用这些新数据结合Byerlee定律的稳定性分析和已有强震前的应力测量资料进行类比,结果表明,大邑地震空区双石-大川断裂带（大川镇）附近处于高地应力状态,具备了摩擦滑动的必要条件,具有发生中、强震的潜在危险性.研究结果揭示了大邑地震空区内1000m深度范围内的地应力剖面,为全面评估地震空区地震危险性提供了全新数据,这对于探索地震发生的机理与减灾具有重要意义.

AbstractAs the eastern boundary of the Tibetan Plateau, Longmen Shan possesses a narrow thrust belt with steep topography but lacks matching Cenozoic foreland basin. Multiple kinetic models have been proposed to debate on the dominant mechanism of developing such range–foreland system. Crustal shortening rate is a feasible approach to test different tectonic models and estimate structural patterns. In this study, we focused on the deformation pattern and shortening rate of the complex foreland area of the southern Longmen Shan, which is comprised of the Xiongpo, Sansuchang, and Longquanshan anticlines. By the means of net-based RTK measurement and Quaternary chronology, we measured and dated the six-level terraces of the Qingyi River, which flows southeastward across this region. Excess area method was applied to calculate shortening rate. The results indicate that the Late Quaternary shortening rates of the Xiongpo anticline, Longquanshan anticline, and Sansuchang anticline are 1.01 mm/yr, 0.89 mm/yr, and 0.16 mm/yr, respectively. The total shortening rate of the foreland in southern Longmen Shan is 2.06 mm/yr. Consequently, a mechanical model was presented to show the tectonic pattern: the southern Longmen Shan is an actively expanding edge of the plateau, and the shortening is distributed to the three anticlines dominated by the foreland detachment system. This model supports that crustal shortening is the dominating force in the current orogenesis of the Longmen Shan. In addition, the along-strike variation of the Longmen Shan was further specified from the perspective of crustal shortening distribution. We propose that the southern Longmen Shan and its foreland basin are in a state of compression, while the northern Longmen Shan has both thrust and strike-slip characteristics.

The Changning M(s)6.0 earthquake and its moderate to strong aftershocks, which occurred in the axial area of Changning anticline, exhibit different features with the moderate to strong earthquakes that occurred in the southern syncline area nearby, although these two areas are only a dozen kilometers away. Whether this difference is only caused by different fault structures, or caused by local change is still a matter of debate. In order to answer this question, basing on the correction of small earthquake location and seismic velocity structure through double-difference tomography inversion, this paper determined the fine structure of the crustal stress field by using comprehensive focal mechanism solutions, and analyzed its mechanical consistency with the focal mechanism solutions of moderate to strong earthquakes. It is found that for the different subareas of Changning area, the maximum principal stress remains horizontal, and its azimuth remains almost East-West oriented although it has a small clockwise rotation from north to south; meanwhile, the stress regime exhibit a significant local change, which is thrust stress regime for the axial area of Changning anticline, against strike-slip stress regime for the southern syncline area. The stress fields in these two subareas highly accord with the focal mechanism solutions of moderate to strong earthquakes in the corresponding area, but poorly accord with, or even contradict that in the non-corresponding area, which indicates that the local stress change of stress field is the necessary mechanical basis for the complex seismicity behavior in Changning area. Additional rock mechanics analysis points out that lateral difference of Poisson's ratio of rock is probably the main cause of this local change of stress field. This paper also discusses the seismogenic fault structure of Changning M(s)6. 0 earthquake sequence, and suggests the activation of the basement fault(s) in the depth range of 6 to 9 km in the axial area of Changning anticline driven by regional stress field is the potential cause of the occurrence of Changning M(s)6. 0 earthquake sequence.

Correlating morphological surfaces, such as terraces and alluvial fans, is necessary in geomorphology researches. Gravel characteristics have been analysed to estimate the weathering degree. However, the composition of gravels was complicated and a feasible quantitative method is still need. Therefore, the objective of this study was to investigate the weathering process of an alluvial fan in western Sichuan Basin and find a practical method in correlating morphological surfaces. The Qingyi River frequently migrated since 500 ka ago and generated several paleo alluvial fans, one of which is the Dansi alluvial fan. Major and trace element samples form an uninterrupted outcrop of the Dansi fan were tested to estimate the weathering process of a single fluvial profile. Results showed that the weathering index decreased regularly with depth, meaning that the surficial sample could represent the weathering degree of the morphological surface. In addition, the sand fillings between the gravels in the river sediments were sensitive to the weathering process and were able to reflect quantitative weathering degree. Therefore, we suggested that the weathering index of the sediments closed to the surface can represent the weathering degree of morphological surfaces.

2015年金口河发生了MS 5.0级地震,为揭示地震与地应力的内在关系和动力学背景,对距震中约12km的2个钻孔的水压致裂地应力测量资料进行了分析研究,利用拜尔利准则和应力莫尔圆分析了峨边-金阳断裂带北部断层的稳定性,并结合地震活动性参数b值探讨了金口河地震发生的动力学背景.研究结果表明:在钻孔94.90～722.10 m的深度内,最大水平主应力为5.89～14.50 MPa,最小水平主应力在3.79～10.30 MPa,应力水平较低;最大水平主应力方向在N50°W～N68°W,趋于北西至北西西向,与区域构造应力场一致;YJP-1孔三向主应力的相对大小表现为有利于逆断层和走滑断层的活动,DPS-1孔三向主应力的相对大小表现为有利于正断层的活动;DPS-1孔有效应力条件下的 μm(最大剪应力与平均应力之比)平均值为0.46,已接近断层摩擦滑动临界值下限0.51,有利于正断层的滑动;峨眉-烟峰断层弯曲构造部位应力闭锁集中区,是导致钻孔附近水平构作用较弱的主要原因.研究结果对于揭示金口河MS 5.0级地震前的动力背景具有重要意义.

本文在综合解译地质图、遥感影像及数字高程模型的基础上,沿着青衣江河谷对龙门山南段多条断裂进行了详细调查.将前第四纪大规模不整合边界作为断裂的分布范围,同时通过构造地貌标志确定最新的活动断裂位置,如断错山脊、断层槽谷、河道形态变化等.解译过程中也参考了前人研究成果,如开挖探槽位置信息,浅层地震剖面资料.调查结果显示,松潘—甘孜褶皱带与龙门山接触地带发育了中岗断裂、永富断裂,晚第四纪活动特征不明显.龙门山后山、中央、前山3条主干断裂在南段依次对应耿达—陇东断裂、岩井—五龙断裂、与双石—大川断裂,与北段具有相似的断块构造.3条断裂都有断错地貌特征但断裂分支较多,其中盐井—五龙断裂有一条分支为宝兴断裂,双石—大川断裂有小关子断裂一条分支.在前陆地区,基底滑脱带延伸至浅部盖层,断坡处发育了始阳断裂、新开店断裂等浅部分支断裂.通过这些断裂分布样式、断错地貌特征、与实测地质剖面发现,龙门山南段具有纯挤压特征,最新构造活动已经开始改造前陆地区,是扩展的边界.而龙门山北段具有和逆冲相当的走滑分量,表明青藏高原在推挤龙门山的过程中,龙门山北缘向西秦岭方向发生走滑逃逸,龙门山南段由于同时受川滇块体向东推挤作用而呈现纯挤压特征.高原推挤作用集中于松潘—甘孜褶皱带东缘的小金弧形构造,控制了龙门山断裂带南北构造差异.

The June 17, 2019 Ms 6.0 Changning earthquake at a depth of 3-5 km struck the Changning anticline fold system. No active faults have been observed in the region. Some studies have attributed the earthquake to the regional shale gas exploitation. Following the earthquake, we conducted a field survey to investigate co-seismic surface deformation in the area, and observed many surface fractures and uplifted areas. Our work indicated that the deformation followed a Riedel shear pattern. The fractures and uplifted areas represent T-fractures and Sextrusions, respectively. The observed Riedel shear pattern is indicative of left-lateral strike-slip motion. To ascertain the relationship between the Riedel shear pattern and regional tectonics, we investigated the trends in layer striations and fault scratches. The results indicated that there were two stages in the evolution of the anticline. In the first stage, the principal compressive stress that dominated the original formation of the anticline trended NE-SW. In the second stage, the regional principal compressive stress shifted to the current E-W trend, generating oblique motion that included reverse and left-lateral components. We propose that the tectonic stress field in this region had a strong bearing on the focal mechanism of the mainshock and the co-seismic surface deformation. Both the eastward expansion of the Xianshuihe area and southeastward expansion of the Longmen Shan have affected the current Changning anticline fold system.

内蒙古自治区克什克腾旗维拉斯托矿区是近年新发现的大型锂锡多金属矿床.矿区深部为Sn、Zn、Rb、Nb、Ta等成矿元素为主体的强云英岩化、天河石化花岗斑岩型矿(化)体;中部为以Li元素为主、伴生Sn、Mo等成矿元素的隐爆角砾岩型矿(化)体;浅部为Sn、W、Zn、Cu、Mo、Ag等成矿元素的热液脉状矿(化)体.多金属矿化受断裂和岩浆热液蚀变双重控制.断裂蚀变分带实测剖面显示,以断裂为中心,两侧蚀变分带对称分布,依次发育硅化、云英岩化、萤石化和碳酸盐化,由此确定蚀变分带:①内带为硅化蚀变岩相带,宽度在2～5m之间,矿体硅化强度高,围岩也发育硅化,浅色矿物变多,暗色矿物减少,岩石变硬变脆,局部可见石英小细脉;②中带为云英岩化蚀变岩相带,宽度在5～10 m之间,云英岩化带发育在硅化带外侧,在矿体与围岩接触部位一般发育结晶粒度较大的云母片,其他部位的云母为细粒类型,包括锂云母、白云母、金云母、绢云母等;③外带为萤石-碳酸盐化蚀变岩相带,宽度一般在20～30 m之间,较大者可达100 m以上;萤石-碳酸盐化蚀变带距矿体较远,多数以细脉状或薄膜状填充在围岩裂隙中.通过对该矿床含矿构造变形岩相带三维空间分布特征的研究,建立起该区构造变形岩相成矿和找矿模型,为下一步地质勘查工作提供新的地质依据.

第四系是与人类生活关系密切的地层,山区地带的第四系主要由河流沉积物组成,这些沉积物的表面风化程度具有重要的环境意义.四川省雅安市地区发育了中更新统砾石层构成的古冲积扇名邛冲积扇和丹思冲积扇,现今废弃于岷江与青衣江之间,遭受了不同程度的侵蚀风化.对两个冲积扇不同位置采集样品,尝试利用主量元素分析冲积扇的风化程度.经过实验发现,主量元素分析可以很好地应用于第四系的测试,砾石间填充的基质砂能够合理反映沉积物经历的风化过程.实验结果表明,沉积物主量元素中长石矿物元素 Ca、Na大量流失,而稳定矿物元素 Si、Ti等偏高,说明冲积扇经历了长期的风化淋溶作用.A－CN－K图解体现出冲积扇经历了早期的斜长石风化,已经进入以钾长石和伊利石风化为标志的中期阶段.Pettijohn图解表明名邛冲积扇样品含有更多的石英砂岩,沉积物的成熟度较高.这些指标说明名邛冲积扇相比丹思冲积扇经历了更强的风化作用.结合冲积扇的年龄发现,风化速度随年龄的增长呈现减速的特征,体现了风化作用的阶段性

上打井斑岩型铜钼矿床发育在中晚侏罗世中细粒斑状二长花岗岩为主要岩性的斑杂岩基中心部位,最大矿化深度800 m;矿石呈细脉浸染状、条带状和块状构造;铜钼矿石中金属矿物有黄铁矿、辉钼矿、黄铁矿、闪锌矿、方铅矿、钛铁矿;从岩体中心向外,热液蚀变类型依次为:钾化、云英岩化、泥化、绿化;其中钾化、云英岩化与铜钼矿化关系密切,铅锌银矿化普遍发育.上打井斑岩型钼矿各成矿阶段的石英细脉中发育丰富的流体包裹体,上打井钼矿的成矿流体为以高温、高盐度、高氧逸度、含CO2为特征的典型岩浆热液型流体.综合研究表明,上打井矿床属典型的斑岩型铜钼矿床,找矿潜力巨大,该矿床成因研究为区域找矿提供可借鉴的范例.