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.     

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.     

Recent progress of seismic research on tall buildings in China Mainland

To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.     

Evaluation of vertical impact factor coefficients for continuous and integral railway bridges under high-speed moving loads

In the railway bridge analysis and design method,dynamic train loads are regarded as static loads enhanced by an impact factor(IF).The IF coefficients for various railway bridges have been reported as a function of span length or frequency of the bridges in Eurocode(2003).However,these IF coefficient values neglect the effects of very high speeds(>200 km/h)and soil-structure interaction(SSI).In this work,a comprehensive study to assess the impact factor coefficients of mid-span vertical displacements for continuous and integral railway bridges subjected to high-speed moving loads is reported.Three different configurations,each for the three-dimensional(3D)continuous and integral bridge,are considered.Also,single-track(1-T)and two-track(2-T)“real train”loading cases for both these bridge types are considered.Subsequently,finite element analysis of the full-scale 3D bridge models,to identify their IF values,considering the effects of SSI for three different soil conditions,is conducted.The IF values obtained from the study for both bridge types are comparable and are greater than the values recommended by Eurocode(2003).The results reveal that with a loss of soil stiffness,the IF value reduces;thus,it confirms the importance of SSI analysis.     

The intrinsic nonlinear multiscale interactions among the mean flow,low frequency variability and mesoscale eddies in the Kuroshio region

Using a new functional analysis tool, multiscale window transform(MWT), and the MWT-based localized multiscale energetics analysis and canonical transfer theory, this study reconstructs the Kuroshio system on three scale windows, namely,the mean flow window, the interannual-scale(low-frequency) window, and the transient eddy window, and investigates the climatological characteristics of the intricate nonlinear interactions among these windows. Significant upscale energy transfer is observed east of Taiwan, where the mean Kuroshio current extracts kinetic energy from both the interannual and eddy windows.It is found that the canonical transfer from the interannual variability is an intrinsic source that drives the eddy activities in this region. The multiscale variabilities of the Kuroshio in the East China Sea(ECS) are mainly controlled by the interaction between the mean flow and the eddies.The mean flow undergoes mixed instabilities(i.e., both barotropic and baroclinic instabilities) in the southern ECS, while it is barotropically stable but baroclinically unstable to the north. The multiscale interactions are found to be most intense south of Japan, where strong mixed instabilities occur; both the canonical transfers from the mean flow and the interannual scale are important mechanisms to fuel the eddies. It is also found that the interannual-scale energy mainly comes from the barotropically unstable jet, rather than the upscale energy transfer from the high frequency eddies.     

Geological and surfacial processes and major disaster effects in the Yellow River Basin

The Yellow River Basin(YRB) is characterized by active geological and tectonic processes, rapid geomorphological evolution, and distinct climatic diversity. Correspondingly, major disasters in the YRB are characterized by varied types,extensive distributions, and sudden occurrences. In addition, major disasters in the YRB usually evolve into disaster chains that cause severe consequences. Therefore, major disasters in the YRB destroy ecologies and environments and influence geological and ecological safety in the basin. This paper systematically reviews research on geological and surface processes, major disaster effects, and risk mitigation in the YRB, discusses the trends and challenges of relevant research, analyzes the key scientific problems that need to be solved, and suggests prospects for future research based on the earth system science concept. Themes of research that should be focused on include geological, surface and climatic processes in the YRB and their interlinking disaster gestation mechanisms;formation mechanisms and disaster chain evolutions of giant landslides in the upper reach of the YRB;mechanisms and disaster chain effects of loess water-soil disasters in the middle reach of the YRB;occurrence patterns and amplifying effects of giant flood chains in the lower reach of the YRB;and risk mitigations of major disasters in the YRB. Key scientific problems that need to be solved are as follows: how to reveal the geological, surface and climatic processes that are coupled and interlinked with gestation mechanisms of major disasters;how to clarify the mutual feedback effects between major disasters and ecology;and how to develop a human-environmental harmony-based integrated risk mitigation system for major disasters. Prospects for future studies that follow the earth system science concept include the following: highlighting interdisciplinary research to reveal the interlinked disaster gestation mechanisms of the geology, surface and climate in the YRB in the past, present, and future;forming theories to clarify the regional patterns, dynamic mechanisms, and mutual-feedback effects between disaster chains and ecology in the YRB on land and in rivers in the region;solving technological bottlenecks to develop assessment models and mitigation theories for integrated risks in the YRB by following the human-environment harmony concept;and finally, establishing a demonstratable application pattern characterized by "whole-basin coverage" and "zonal controls", thereby guaranteeing ecological and geological safety in the basin and providing scientific support for ecological conservation and high-quality development of the YRB.     

Distribution and structural characteristics of the Xi'an Section of the Weihe Fault

The results of seismic deep reflection,high resolution refraction and shallow artificial seismic exploration indicate that the fault on the northern bank of the Weihe river is composed of two faults,one is the Yaodian-Zhangjiawan fault and the other is the Chuanzhang-Zuitou fault.The 22 km long Yaodian-Zhangjiawan fault of EW-striking starts from Chenjiagou via Yaodian town,Qianpai village,Bili village,Wujia town and Zhangjiawan to Jiajiatan.The 15 km long Chuanzhang-Zuitou fault striking near EW starts from Chuanzhang via Mabei to Zuitou.The Weihe fault offset the basement and upper crust,the reflecting layers of TQ,TN,TE and Tg are ruptured at depth of about 15 km.In the deep part,the Weihe fault and the secondary fault form a Y-shaped structure or a synthetic low angle intersection.The Weihe fault is a listric normal fault.The fault has obvious structural characteristics of a reversed-drag normal fault and a normal drag normal fault with the depth of 1 000 m,and also has the characteris-tics of syngenetic sediment.The Weihe fault is one of the faults which control the basin sediment,and it is the boundary fault of Xi’an depression and Xianyang salient.The depth of the fault decreases from the west to east gradually,the deep part intersects with the Lintong-Chang’an fault at the intersection part of Weihe River,Jinghe River and Bahe River and the shallow part connects with the Weinan-Jingyang fault.The seismic exploration re-sults indicate that no fault exists on southern bank of the Weihe River.     

Prestack reverse-time depth migration of arbitrarily wide-angle wave equations

Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques,a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is applicable of dip angle reflector imaging.     

Evaluation of the fishbone model in simulating the seismic response of multistory reinforced concrete moment-resisting frames

The fishbone model is a simplified numerical model for moment-resisting frames that is capable of modelling the effects of column-beam strength and stiffness ratios. The applicability of the fishbone model in simulating the seismic responses of reinforced concrete moment-resisting frames of different sets of column-beam strength and stiffness ratios are evaluated through nonlinear static, dynamic and incremental dynamic analysis on six prototype buildings of 4-, 8-and 12-stories. The results show that the fishbone model is practically accurate enough for reinforced concrete frames, although the assumption of equal joint rotation does not hold in all cases. In addition to the ground motion characteristics and the number of stories in the structures, the accuracy of the model also varies with the column-beam stiffness and strength ratios. The model performs better for strong column-weak beam frames, in which the lateral drift patterns are better controlled by the continuous stiffness provided by the strong columns. When the inelastic deformation is large, the accuracy of the model may be subjected to large record-to-record variability. This is especially the case for frames of weak columns.     

Causes and underlying dynamic processes of the mid-winter suppression in the North Pacific storm track

Baroclinic wave activity in the North Pacific exhibit peaks in late fall and early spring, and a local minimum in midwinter, when by linear baroclinic instability theory it should attain its maximum. This counterintuitive phenomenon, or"midwinter suppression"(MWM) as called, is investigated with a functional analysis apparatus, multiscale window transform(MWT), and the MWT-based theory of canonical transfer and localized multi-scale energetics analysis, together with a feature tracking technique, using the data from the European Centre for Medium-Range Weather Forecasts ReAnalysis(ERA-40). It is found that the MWM results from a variety of different physical processes, including baroclinic canonical transfer, diabatic effect, energy flux divergence, and frictional dissipation. On one hand, baroclinic canonical transfer and diabatic effect achieve their respective maxima in late fall. More transient available potential energy is produced and then converted to transient kinetic energy, resulting in a stronger storm track in late fall than in midwinter. On the other hand, in early spring, although baroclinic instability and buoyancy conversion are weak, energy flux convergences are substantially strengthened, leading to a net energy inflow into the storm track. Meanwhile, frictional dissipation is greatly reduced in spring; as a result, less transient energy is dissipated in early spring than in midwinter. It is further found that the weakening of baroclinic canonical transfer in midwinter(compared to late fall) is due to the far distance between the storm and the jet stream(located at its southernmost point), which suppresses the interaction between them. Regarding the increase in energy flux convergence in early spring, it appears to originate from the increase(enhancement) in the number(strength) of storms from the upstream into the Pacific.     

澜沧—耿马地震前地震熵异常研究

本文将地震系统作为开放系统进行研究,认为系统和外界有物质和能量的交流,导致孕震区滑向不稳定的非平衡态,然后在各种涨落扰动下发生地震。本文研究1988年澜沧——耿马地震、1976年龙陵、宁蒗地震、1974年昭通地震、1970年通海地震孕震区,得到大震孕育调整模型,大震前地震开放系统熵值曲线变化特征,可作为大震预报指标应用于日常监测工作中。     

震群活动和地震预报综述

研究震群和大地震的关系、用前兆震群预报未来地震的发生,是世界范围内比较活跃的课题之一。文章例举了震群的一些指标以说明前兆性震群的预报意义,并从大范围的众多震群活动阐述大震前震群活动的一些特征。根据震群的分布可确定未来大震的发生地点,并解释不同类型震群的力学成因。     

海城地震前震系列与震群——兼论前震系列在地震预报中的一种功能

对比了海城前震系列与其周围同期震群的异同.两者的震源空间分布都比较集中,一般只有几公里的尺度.发震机制都比较稳定.但有些震群在其主要地震发生后,机制变化较显著,借此有可能识别一部份震群.但也有些震群其机制的稳定性始终不比海城前震系列差,因之借此无法识别前震系列.频次的分布两者也有非常相似的震例.总的印象是有些震群在晚期有可能识别,但未发现有确认前震(系列)的肯定判据.这一初步的结论仅仅是由于我们分辨技术的局限,抑是具有成因上的深刻含义是很值得思考的.最后引入了震级序列的缺震特征,借此可以判断系列的高潮是否已经渡过.这对(从其他证据认识到的)具有大震危险的地区,利用前震系列来改善大震临震时刻的机率性判断是有用的.注意到频次分布中有相隔12小时的低值点,对比就地的固体潮具有较好的同步性,说明固体潮可能对前震系列以及震群具有触发作用.      

地震集群分析法研究及其在海河断裂中的应用

对地震震中资料进行集群分析,确定线状构造,可以查明活断层。本文对天津—渤海地区的地震资料进行处理,勾画出地震线,从而提供了天津蓬莱断裂（海河断裂）是ＮＷＷ向规模宏大的活动断裂的一个证据。     

减轻地震灾害://c

回顾了过去4年来中国在减轻地震灾害方面的研究进展．地震灾害定量化的研究结果表明，随着社会经济的发展和人口城市化的加快，地震造成的灾害将越来越严重．减轻地震灾害的研究，出现了一些新的趋势:从研究地震危险性向研究地震危害性的过渡；从研究工程灾害向研究社会灾害的过渡；以及发展了以社区为中心的减灾体系．      

张北6.2级地震的防震减灾问题讨论

通过对张北地震未能作出短临界预报的反思,建议在地震危险区和重点监视区加强对全民的地震知识宣传与普及,提高全民的防震减灾意识;加强宏观监测,在恢复和重建家园工作中重视抗震设施的问题。     

1975年海城7.3级地震应急工作述评

地震应急对减轻地震灾害有重要作用,我国的地震应急始于1966年邢台地震,辽宁省的地震应急是从1975年海城7.3级地震以前开始的。本文全面介绍了1975年海城7.3级地震的应急工作,并对这次工作的效果和存在的不足作了评述。文章认为,海城地震应急工作是一次有成效的地震应急实践。它为辽宁省地震应急救援提供了经验,也为地震应急救援体系的建设奠定了坚实的基础。     

海丰震群发震构造型式的讨论

海丰震区发育着规模宏大的 NE 向海丰——梅陇断裂及一系列与其平行的次级断裂.同时,还存在与其共轭的断续分布的 NW 向断裂.震群中的三个子群的主震的震源机制解非常类似,其中一节面为 NE,另一节面为 NW.从余震的空间分布及极震区的长轴方向来看,2月26日 ML3.3和4月9日 MLL,4.2地震的断层面为 NE 向;而3月14日 ML,3.4地震,其断层面应取 NW 向.又据137个小震的四个台的 P 波初动符号的组合特征,可划分为八个类型并作出相应的迭加震源机制解.综上所述,本区破裂过程,主震及Ⅰ、Ⅳ 类地震是岩块沿NE 及 NW 向共轭构造的粘滑;Ⅱ——Ⅴ、Ⅶ、Ⅷ 类地震是岩块在粘滑过程中对前后邻接岩块引起平行滑动方向的挤压(前)和引张(后)的转换应力场所产生的剪切破裂.      

1850年西昌地震地表破裂带

着重从 1850年西昌地震的地表破裂带调查入手 ,通过对地表破裂的分布特征、几何特征以及与各次级断层的关系的研究 ,对这次地震的震级、震中位置和震源深度进行讨论。     

1850年西昌地震地表破裂带

着重从1850年西昌地震的地表破裂带调查入手,通过对地表破裂的分布特征、几何特征以及与各次级断层的关系的研究,对这次地震的震级、震中位置和震源深度进行讨论。