A new era of flood control strategies from the perspective of managing the 2020 Yangtze River flood

Flood control of the Yangtze River is an important part of China’s national water security.In July 2020,due to continuous heavy rainfall,the water levels along the middle-lower reaches of the Yangtze River and major lakes constantly exceeded the warning levels,in which Taihu Lake exceeded its highest safety water level and some stations of Poyang Lake reached their highest water levels in its history.In August 2020,another huge flood occurred in the Minjiang River and the Jialing River in the upper Yangtze River,and some areas of Chongqing Municipality and other cities along the rivers were inundated,resulting in great pressure on flood control and high disaster losses.The 2020 Yangtze River flood has received extensive media coverage and raised concerns on the roles of the Three Gorges Dam and other large reservoirs in flood control.Here we analyze the changes in the pattern of the Yangtze River flood control by comparing the strategies to tackle the three heavy floods occurring in 1954,1998,and 2020.We propose that the overall strategy of the Yangtze River flood control in the new era should adhere to the principle of"Integration of storage and drainage over the entire Yangtze River Basin,with draining floods downstream as the first priority"by using both engineering and non-engineering measures.On the basis of embankments,the engineering measures should use the Three Gorges Dam and other large reservoirs as the major regulatory means,promote the construction of key flood detention areas,keep the floodways clear,and maintain the ecosystem services of wetlands and shoals.In terms of non-engineering measures,we should strengthen adaptive flood risk management under climate change,standardize the use of lands in flood detention areas,give space to floods,and promote the implementation of flood risk maps and flood insurance policies.The ultimate goal of this new flood control system is to enhance the adaptability to frequent floods and increase the resilience to extreme flood disasters.     

The soil Microbial Carbon Pump as a new concept for terrestrial carbon sequestration

Soil is a huge terrestrial carbon pool, which has higher carbon storage than the sum of atmospheric and terrestrial vegetation carbon. Small fluctuations in soil carbon pool can affect regional carbon flux and global climate change. As soil organic carbon plays key roles in soil carbon storage and sequestration, studying its composition, sources and stability mechanism is a key to deeply understand the functions of terrestrial ecosystem and how it will respond to climate changes. The recently-proposed concept of soil Microbial Carbon Pump(MCP) emphasizes the importance of soil microbial anabolism and its contributions to soil carbon formation and stabilization, which can be applied for elucidating the source, formation and sequestration of soil organic carbon. This article elaborates MCP-mediated soil carbon sequestration mechanism and its influencing factors, as well as representative scientific questions we may explore with the soil MCP conceptual framework.     

Geophysical evidence for thrusting of crustal materials from orogenic belts over both sides of the Yangtze Block and its geological significance

Based on deep geophysical detections, we have reconstructed the crustal structure from the eastern margin of the Tibetan Plateau to the Jiangnan-Xuefeng orogenic belt. The results suggest that the Yangtze Block was overthrusted by crustal materials in its NW direction from the eastern Tibetan Plateau but in its SE direction from the Jiangnan orogen. These overthrusting effects control the crustal structure from the western Sichuan to the western area of the Jiangnan orogen-Xuefeng orogenic belt. The eastward extruded materials from the eastern Tibetan Plateau were blocked by the rigid basement in the Sichuan Basin, where upper-middle crust was overthrusted whereas the lower crust was underthrusted beneath the Sichuan Basin. The underthrusted unit was absorbed by crustal folding, shortening and thickening in the Yangtze Block, forming the Xiongpo and Longquan Mountains tectonic belts and resulting in the NW-directed thrusting of the Pujiang-Chengdu-Deyang fault, and the western hillsiden fault in the Longquan Mountain. These results provide resolution to the controversy where the eastward extrusion material from the Qinghai-Tibet Plateau had gone. Overall, that Yangtze Block was subjected to thrusting of the crustal materials from the orogenic belts over its both sides. This finding has implications for the study of the intracontinental orogenic mechanism in South China, the reconstruction of tectonic evolutionary history and the kinematics processes during the lateral extrusion of the Tibet Plateau.     

Variations of widespread extreme cold and warm days in winter over China and their possible causes

The two leading modes of winter surface air temperature(SAT) over China during 1961–2017 are a spatially consistent pattern and a north-south dipole pattern. Based on the two leading modes, the characteristics of the extreme cold and warm days in the two patterns, defined by the standard deviation larger than 1.28 or smaller than-1.28 in the time series of the two leading modes, are analyzed. With the increase of winter SAT during 1961–2017, the number of spatially consistent extreme cold days decreased and their occurrence was restricted to late December to early January, whereas the number of spatially consistent extreme warm days increased significantly in January and February. Global warming is associated with an increase in the spatially consistent extreme warm days and a decrease in spatially consistent extreme cold days, but has little relation to the sum of extreme cold and warm days of either the spatially consistent or north-south dipole pattern. The Siberian High(SH) is the main factor controlling the sum of spatially consistent extreme warm and cold days. The strong(weak) SH before(after) the1990 s corresponds to an increase(decrease) in the sum of the spatially consistent extreme warm and cold days. The occurrences of extreme south-cold-north-warm and extreme south-warm-north-cold days are related to the north-south difference of the SH.When the center of the SH is in mid-high latitudes, the extreme south-warm-north-cold(south-cold-north-warm) days occur more(less) often. During the winters of 1961–2017, the total number of extreme cold and warm days of the north-south dipole pattern changes negligibly. The North Atlantic meridional overturning circulation(AMOC) may be the main factor affecting the sum of the extreme cold and warm days of the two types of SAT pattern in China.     

Detailed mapping of the surface rupture of the 12 February 2014 Yutian Ms7.3 earthquake,Altyn Tagh fault,Xinjiang, China

Large-scale detailed mapping plays a key role in revealing the rupture characteristics and mechanisms of strong earthquakes.Relatively few studies have been performed on the surface ruptures of large earthquakes in central and western Tibet due to its remote nature and high elevation.Based on high-resolution unmanned aerial vehicle(UAV)photography,we mapped the coseismic surface rupture of the 2014 Yutian M_s7.3 earthquake.Along the western Altyn Tagh fault system,the earthquake produced~37 km of surface rupture along the South Xor Kol fault(southern section S1),Xor Kol fault(central section S2)and Ashikule fault(northern section S3).Section S1 has a 16-km-long surface rupture with an average sinistral offset of 52±25 cm and a maximum offset of~90 cm,while section S3 has a 14.2-km-long surface rupture with an average sinistral offset of 36±21 cm and a maximum offset of~84 cm.A compilation of 5308 cracks yields an average crack width along the southern section of 85±71 cm and a maximum width of~700 cm;the average width along the central section is 39±21 cm,and the maximum width is 243 cm;and the average width along the northern section is 61±44 cm with a maximum of~340 cm.In addition,the average cumulative opening across rupture zone is 3.4±2.9 m along the southern section,with a maximum of~17 m;4.3±3.6 m along the central section,with a maximum of~13 m;and 1.7±1.6 m along the northern section,with a maximum of~6 m.Evidently,the average crack width and cumulative opening decrease towards bends and steps along the fault.A global synthesis of surface rupture distributions corresponding to strike-slip earthquakes indicates that the rupture zone is wider near the complex parts of fault geometries(such as bends,steps and fault bifurcations)than along straight sections,suggesting that the fault geometry has an obvious control on the surface rupture width.The widespread cracks at the intersection between the Xor Kol and South Xor Kol faults may indicate that an extensional regime is more likely to produce distributed offfault deformation,which provides an observational constraint for the numerical simulation of dynamic rupture on a fault.In addition to coseismic surface rupture,the Yutian earthquake also produced a large number of gravity-driven slides on alluvial fans with gentle slopes.The friction efficiency of the water-bearing salt layer beneath fans could decrease the sliding threshold and trigger instability under surface shaking.These distributed deformations and gravity-driven slides reflect the coupling between the rupture propagation and fault geometry and indicate that the rupture may have propagated in two directions along the Ashikule fault after passing through a step.Therefore,the investigation of coseismic surface rupture provides important observational constraints on the dynamic rupture process.     

Coupled and splitting bedload sediment transport models based on a modified flux-wave approach

Numerical modeling of free-surface flow over a mobile bed with predominantly bedload sediment transport can be done by solving the shallow water and Exner equations using coupled and splitting approaches.The coupled method uses a coupling of the governing equations at the same time step leading to a non-conservative solution.The splitting method solves the Exner and the shallow water equations in a separate manner,and is only capable of modeling weak free-surface and bedload interactions.In the current study,an extended version of a Godunov-type wave propagation algorithm is presented for modeling of morphodynamic systems using both coupled and splitting approaches.In the introduced coupled method the entire morphodynamic system is solved in the form of a conservation law.For the splitting technique,a new wave Riemann decomposition is defined which enables the scheme to be utilized for mild and strong interactions.To consider the bedload sediment discharge within the Exner equation,the Smart and Meyer-Peter&Müller formulae are used.It was found that the coupled solution gives accurate predictions for all investigated flow regimes including propagation over a dry-state using a Courant-Friedrichs-Lewy(CFL)number equal to 0.6.Furthermore,the splitting method was able to model all flow regimes with a lower CFL number of 0.3.     

Numerical simulations of shake-table experiment for dynamic soil-pile-structure interaction in liquefiable soils

A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements.     

Existence,morphology and structure of the Yellow Sea Warm Current Branch approaching waters offshore Qingdao,China

In this study, we focused on full-region cruise survey data, near-bottom continuous mooring observations and sea surface wind products from the western South Yellow Sea in winter; after ensuring the data reliability and accuracy, we processed and analyzed the data. Image resolution experiments were carried out to determine the lowest recognition resolutions for all image types, which represent the resolution characteristics of the data. The existence of a warm water tongue originating from the Yellow Sea Warm Current(YSWC) that approached waters offshore Qingdao was confirmed. For the first time, a high salinity water tongue, corresponding to the warm water tongue, was described and found to be more representative of the YSWC branch path. This warm tongue is a sign of the branch originating from the YSWC, which we defined as the Yellow Sea Warm Current Branch approaching waters offshore Qingdao(YSWC-QDB). The pattern of the warm and salty water tongues showed remarkable rear, branching middle, shrinking neck and expanding top regions. These patterns showed a temporal feature of the tongues, and were the result of multi-temporal branches in front of the YSWC main section as well as the YSWC-QDB crossing the southwestward path of the extension of the North Shandong Coastal Current flowing along the southeast coast of the Shandong Peninsula(NSCC-SESE). Analysis using mooring data at a sensitive and representative station also showed the existence of the YSWC-QDB. It is a probabilistic event that manifests as a northwestward flow that decreases gradually from the bottom to the surface in the early cold air transit stage and consistent in the whole water column profile in the later stage. It varies quasi-periodically with weather processes. It also transports some of the YSWC water stored in the entrance area of the Bohai and Yellow seas under winter wind conditions to the western South Yellow Sea as a compensatory current. This current, caused by northerly winds, especially northwest winds and obstruction of the NSCC-SESE, was present, and strong water reduction and compensation caused significant residual sea level oscillations. The compensatory current, if caused by strong northwest wind,began to appear when its direction was opposite to the wind direction. In addition, confirmation of the YSWC-QDB provides an oceanographic basis for the short cooling time and rapid warming in the Qingdao area in winter. This research provides a basis for further studies of the YSWC-QDB at high spatial and temporal resolutions using large sea surface datasets. For monsoon basin dynamics, this study can also be extended to the whole Bohai and Yellow seas and closed or semi-closed basins on the continental margin.     

Review of Mercury's dynamic magnetosphere:Post-MESSENGER era and comparative magnetospheres

This review paper summarizes the research of Mercury’s magnetosphere in the Post-MESSENGER era and compares its dynamics to those in other planetary magnetospheres,especially to those in Earth’s magnetosphere.This review starts by introducing the planet Mercury,including its interplanetary environment,magnetosphere,exosphere,and conducting core.The frequent and intense magnetic reconnection on the dayside magnetopause,which is represented by the flux transfer event"shower",is reviewed on how they depend on magnetosheath plasma β and magnetic shear angle across the magnetopause,followed by how it contributes to the flux circulation and magnetosphere-surface-exosphere coupling.In the next,Mercury’s magnetosphere under extreme solar events,including the core induction and the reconnection erosion on the dayside magnetosphere,as well as the responses of the nightside magnetosphere,are reviewed.Then,the dawn-dusk properties of the plasma sheet,including the features of the ions,the structure of the current sheet,and the dynamics of magnetic reconnection,are summarized.The last topic is devoted to the particle energization in Mercury’s magnetosphere,which includes the energization of the Kelvin-Helmholtz waves on the magnetopause boundaries,reconnection-generated magnetic structures,and the cross-tail electric field.In each chapter,the last section discusses the open questions related to each topic,which can be considered by the simulations and the future spacecraft mission.We end this paper by summarizing the future Bepi Colombo opportunities,which is a joint mission of ESA and JAXA and is en route to Mercury.     

地震日常分析会商数据库管理软件

介绍了地震日常分析会商数据库管理软件研制的思路.该软件构建了最优的数据库表结构和Excel模板,实现了会商登记卡、震情监视报告、首都圈地区震情短临跟踪动态等信息的浏览、新添、删除、修改、保存、打印,具有首都圈地区各学科异常频次自动统计、绘图等功能.     

晚第四纪以来安宁河断裂的构造活动与演化

在进行１：５万地质填图过程中,通过对安宁河断裂区域内晚更新世 一新世地层岩性,岩极及组成的各级地貌特征并结合地层的对年龄测定较为实际的研究与划分了断裂的活动期,次,并据此进一步研究了断裂活动的性质,方式与演化简史。     

渭河盆地东南缘铲形正断层上盘活动特征

本文根据野外和力学分析，认为渭河盆地东南缘铲形正断层上盘块体沿凹曲的断层面向下滑动和旋转作用，在山前冲洪积平原区产生了同向断层、反向断层和上盘横断层。这些构造的差异活动及其在地表的表现特征，可作为铲形正断层分段的重要标志。     

新疆库尔勒活动断裂和断层破裂段探讨

新疆南疆重镇库尔勒市及附近地区，至少分布着９条颇具规模的活动断裂。尤其斜切库尔勒市区北部的库尔勒断裂，新活动十分强烈。库尔勒断裂东段与兴地断裂西段很可能是连通的一条地震破裂段，两者均存在着丰富的多期次古地震事件的遗迹，为较稳定的断层“破裂单元”。该破裂段上现代地震活动异常平静，但发现了明显的蠕滑错开形迹。这种地震的发生与断层滑动不协调现象，说明断层运动受到了抑制，能量在某处得以积累，有酿成大震的条件和危险。     

朝鲜北西部地质构造特征及主要断裂活动性

着重论述了朝鲜北西部五条主要断裂的活动性、简要地叙述了这些断裂的概略特征,认为北东向的鸭绿江东支断裂、清川江断裂为中、晚更新世有活动,早更新世有明显活动的断裂;北西向的载宁江断裂为中更新世有活动,早更新世有明显活动的断裂;在北西西向断裂中,长林断裂为早更新世—上新世活动断裂,南江断裂活动时代不详。其活动性最明显的为鸭绿江东支断裂和载宁江断裂,次为清川江断裂和长林断裂,再是南江断裂。最后,还讨论了这些断裂的形成与演化。     

安宁河断裂带晚第四纪运动特征及模式的讨论

安宁河断裂带是中国西南地区一条重要的地震活动断层， 地方志记载公元1536年曾发生过震级大于7级的破坏性地震. 详细的断裂地貌航片解译和野外调查表明， 安宁河断裂带除具有主要的左旋走滑断层活动外，还兼有重要的逆冲运动分量. 根据冲沟和阶地面的位错量及其热释光测年结果估计，该断裂带晚更新世以来平均左旋走滑速率为3~7 mm/a. 根据滑移方向与断层走向的关系，推测跨安宁河断裂带东西向由于逆冲断层运动造成的挤压缩短速率约为1.7~4.0 mm/a； 简单分解鲜水河断裂带上的滑动速率，估计分配在大凉山断裂带上的滑动速率与安宁河断裂带上的大致相当，约为3~7 mm/a. 此外，根据野外调查结果，并结合最近青藏高原构造动力学研究的新认识， 建立了安宁河断裂带的动力学模型，认为安宁河断裂带是一条逆冲走滑断裂带. 其下盘（西盘）主动向南东方向下插，造成了上盘（东盘）向北西方向的上冲运动.      

土壤氡对郯庐断裂宿迁段F5断裂探测和活动性的研究

郯庐断裂带宿迁段多年来一直被列为江苏地震重点关注区域。在该区域展开了多期活断层探测和工程地震安全性评价工作,地震监测已经建成了测震、形变、电磁、流体等多种手段。用气体地球化学方法开展相关研究,探索活动断层运动和地震发生之间的相互关系,是对该地区地震科学研究的一种补充,其有着十分重要的意义。沿郯庐断裂带宿迁段F₅断裂布设土壤氡测线并获得相关数据,结合地质勘察、浅层人工地震等资料进行综合分析,结果表明该区域内土壤氡探测结果对断裂带的位置、断层类型和特征、断层活动性具有较好的指示性。土壤氡探测展示F₅断裂两条分支断裂F_5-1、F_5-2的位置,氡浓度异常形态与断层特征存在一定的对应关系,并利用土壤氡浓度强度为指标,初步判断郯庐断裂带宿迁段F₅断裂2条分支断裂的相对活动性。     

滇西南地区汉母坝-澜沧断裂晚第四纪构造活动的地质地貌证据

通过对汗母坝-澜沧断裂晚第四纪地质、地貌实地调查与测量,并结合前人研究成果,讨论了该断裂晚第四纪最新构造活动特征。综合分析认为,汗母坝-澜沧断裂为一条以右旋走滑为主的全新世活动断裂,长约120 km,整体走向NNW。该断裂活动习性具有明显的分段特征,北段称为汗母坝断裂,是1988年耿马7.2级地震的发震断裂;南段称为澜沧断裂,是1988年澜沧7.6级地震的发震断裂之一。晚第四纪以来其新活动形成了丰富的断错地貌现象,如冲沟和山脊右旋位错、断层沟槽、断层垭口、断层陡坎、断陷凹坑等。根据断裂断错地貌特征的相应资料估计,该断裂晚第四纪右旋走滑速率约为(4.7±0.5) mm/a。     

Faulting on the Anninghe fault zone, Southwest China in Late Quaternary and its movement model

The Anninghe fault is one of the significant earthquake-generating fault zones in the Southwest China. Local his-torical record shows that a M≥7 strong earthquake occurred in the year of 1536. On the basis of the detailed air-photographic interpretation and field investigation, we have acquired the following knowledge: 1 The average sinistral strike-slip rate since the Late Pleistocene is about 3~7 mm/a; 2 There is important reverse faulting along the fault zone besides the main left-lateral strike-slip motion, and the shortening rate across the Anninghe fault zone due to the reverse faulting is about 1.7~4.0 mm/a. If the Xianshuihe fault zone is simply partitioned into the Anninghe and Daliangshan faults, we can also get a slip rate of 3~7 mm/a along the Daliangshan fault zone, which is the same as that on the Anninghe fault zone. Moreover, on the basis of our field investigation and the latest knowledge concerning the active tectonics of Tibetan crust, we create a dynamic model for the Anninghe fault zone.     

Analysis of Geological Background of Seismic Activity in the Chengdu Plain from Data of Seismic Prospecting for Oil

Summarizing the existing data of seismological and geological investigations and of strong and intermediate-strong earthquakes in‘ the Sichuan basin and its adjacent areas accumulated by the seismological and petroleum organizations in Sichuan and of the results of seismic prospecting and detailed exploration in Chengdu depression during the last 20 years permitted us to studythe types and distribution of hidden structures in Chengdu depression and its adjacent areas, in particular, to identify in, detail the “hidden faults” in the Chenngdu-Deyang area on the one hand; The obtained data indicate that the NE-trending Xinjin fault ruus northward and dies out in the south of Penzhen town of Shuangliu County; Meanwhile, we studied genetic relations of seismic activity to active faults and their corresponding movernent charaeteristics on the other hand, Moreover, the Surface faults and deep-seated faults are clearly defined and outlined,and 5 types of seismogenic faults suggestd. The knowledge thus obtained enables us to delimit the focal zones for potential strong earthquakes in Chengdu depression. The study suggests that a zone of 40 km wide and more than 100 km long on sides along the Chengu Deyang lim bas a stable seismogeological background and good engineering-seismological conditions.     

Crustal deformation of seismogenic fault and its surrounding area after the Tangshane arthquake

ＣｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｏｆｓｅｉｓｍｏｇｅｎｉｃｆａｕｌｔａｎｄｉｔｓｓｕｒｏｕｎｄｉｎｇａｒｅａａｆｔｅｒｔｈｅＴａｎｇｓｈａｎｅａｒｔｈｑｕａｋｅＪＵＥＭＩＮＸＩＥ（谢觉民）ＲＵＯＢＡＩＷＡＮＧ（王若柏）ＷＡＮＧＪＵＢＯ（...