Three-dimensional velocity structure and tectonic characteristics of earthquake area in Yibin

In this study,on the basis of absolute first-arrival times of 84756 P-and S-waves from 6085 earthquakes recorded at 56 fixed stations in Yibin and surrounding areas in China from January 2009 to January 2019,focal parameters and three-dimensional(3 D)body-wave high-resolution velocity structures at depths of 0–30 km were retrieved by double-difference tomography.Results show that there is a good correspondence between the spatial distribution of the relocated earthquakes and velocity structures,which were concentrated mainly in the high-velocity-anomaly region or edge of high-velocity region.Velocity structure of P-and S-waves in the Yibin area clearly shows lateral inhomogeneity.The distribution characteristics of the P-and S-waves near the surface are closely related to the geomorphology and geologic structure.The low-velocity anomaly appears at the depth of 15–25 km,which is affected by the lower crust current.The Junlian–Gongxian and Gongxian–Changning earthquake areas,which are the two most earthquake-prone areas in the Yibin region,clearly differ in earthquake distribution and tectonic characteristics.We analyzed the structural characteristics of the Junlian–Gongxian and Gongxian–Changning earthquake areas on the basis of the 3 D bodywave velocity structures in the Yibin region.We found that although most seismicity in the Yibin area is caused by fluid injection,the spatial position of seismicity is controlled by the velocity structures of the middle and upper crust and local geologic structure.Fine-scale 3 D velocity structures in the Yibin area provide important local reference information for further understanding the crustal medium,seismogenic structure,and seismicity.

Application of Characteristics of Seismogenic Structures in the Determination of Parameter of Potential Seismic Source Areas

The characteristics of seismogenic structures are an important basis for delineating the potential seismic source areas and determining the annual occurrence rate of earthquakes. The potential seismic source area does not only have the intension that “this area has the possibility for destructive earthquakes to occur in the future" but also means that earthquakes of high magnitude interval have the characteristics of similar recurrence. When determining the seismic activity parameters of a statistical unit, some active tectonic blocks in the unit may have different background earthquakes. In order to better reflect the heterogeneity in space of seismic activities, it is necessary to divide the potential seismic source areas into three orders. By analyzing the recurrence characteristics of earthquakes of high magnitude interval in the potential source area and calculating the occurrence probability of earthquakes of high magnitude interval in the potential seismic source area in the time window for prediction, the average annual occurrence rate of earthquakes can be obtained by the method of probability equivalent conversion in the time window for prediction. This would be helpful for considering the recurrence characteristics of strong earthquakes in potential source areas within the framework of seismic risk analysis of China. Besides, the insufficient frequency of characteristic earthquakes of the next high magnitude interval in the potential source area and the heterogeneity of strong earthquakes on seismogenic structures are analyzed to see their application in seismic risk analysis.

Spatial-temporal Heterogeneity of Industrial Structure Transformation and Carbon Emission Effects in Xuzhou Metropolitan Area

Employing decoupling index and industrial structure characteristic bias index methods, this study analyzed the spatial-temporal characteristics of industrial structure transformations and their resulting carbon emissions in the Xuzhou Metropolitan Area from 2000 to 2014, with a focus on their relationships and driving factors. Our research indicates that carbon emission intensity from industrial structures in the Xuzhou Metropolitan Area at first showed an increasing trend, which then decreased. Furthermore, the relationship between emissions and industrial economic growth has been trending toward absolute decoupling. From the perspective of the center-periphery, the Xuzhou Metropolitan Area formed a concentric pattern, where both progress towards low emissions and the level of technological advancement gradually diminished from the center to the periphery. In terms of variation across provinces, the ISCB index in the eastern Henan has decreased the slowest, followed by the southern Shandong and the northern Anhui, with the northern Jiangsu ranking last. During this period, resource-and labor-intensive industries were the primary growth industries in the northern Anhui and the eastern Henan, while labor-intensive industries dominated the southern Shandong and capital-intensive industries dominated the northern Jiangsu. In terms of city types, the spatial pattern for industrial structure indicates that recession resource-based cities had higher carbon emission intensities than mature resource-based cities, followed by non-resource-based cities and regenerative resource-based cities. Generally, the industrial structure in the Xuzhou Metropolitan Area has transformed from being resource-intensive to capital-intensive, and has been trending toward technology-intensive as resource availability has been exploited to exhaustion and then been regenerated. Industrial structure has been the leading factor causing heterogeneity of carbon emission intensities between metropolitan cities. Therefore, the key to optimizing the industrial structure and layout of metropolitan areas is to promote industrial structure transformation and improve the system controlling collaborative industrial development between cities.

COMPARISON OF THE STRUCTURAL CHARACTERISTICS OF DEVELOPED VERSUS UNDEVELOPED MID-LEVEL VORTEXES

Using the NCEP 1°×1°reanalysis data,several obvious differences of the structural characteristics of developed versus undeveloped mid-level vortexes are studied.First,the central vorticity of the developed mid-level vortex increases towards higher levels while the undeveloped one decreases.The low-level convergence structure maintains well in the developed mid-level vortex whereas the undeveloped one does badly.Second,on the one hand,according to the symmetric analysis,the horizontal wind field and wind vertical section of the developed mid-level vortex are well symmetric while those of the undeveloped one are less symmetric.Meanwhile,weak wind vertical shear help the developed mid-level vortex to establish a warm core in upper-and mid-levels of the troposphere.On the other hand,according to the balance analysis,better balance between wind and pressure is shown in the mid-and lower-levels of the troposphere of the developed mid-level vortex than in those of the undeveloped vortex.Third,positive anomaly of potential vorticity is enhanced and developed in the vertical direction of the developed vortex.However,the undeveloped vortex weakens with a weak positive anomaly.

Emergency road network structure and planning optimization in mountainous regions in Southwest China under earthquake scenarios

Emergency road networks(ERNs),an important part of local disaster prevention systems,can provide security to residents and their property.Exploring the ERNs structure is of great significance in terms of promoting disaster prevention and establishing road safety in dangerous mountainous areas.This study considered the ERNs of the Kangding section of the Dadu River Basin as the area for a case study.Complex Network Analysis was used to examine the relationship between the four characteristic indicators of mountain roads and the degree of earthquake impacts under the Lushan,Wenchuan,and Kangding Earthquake scenarios.Based on the analysis results,the southwest mountain road network was evaluated;then,computer simulations were used to evaluate the structural changes in the road network after index changes.The network was optimized,and the corresponding emergency avoidance network was proposed to provide a reference for the establishment of the mountainous ERN.The results show that the overall completeness of the mountainous ERNs in Southwest China is poor and prone to traffic accidents.Moreover,the local stability is poor,and the network is susceptible to natural hazards.The overall structure of the road network is balanced,but that of certain road sections is not.Road sections with different attributes present a“gathering-scattering”spatial distribution,i.e,some sections are clustered together while others are far apart.Accordingly,a planning optimization strategy is proposed to better understand the complexity and systematic nature of the mountainous ERN as a whole and to provide a reference for disaster prevention and mitigation planning in mountainous regions in Southwest China.

Hydrodynamic Characteristics of the Biplane-Type Otter Board with the Canvas Through Flume−Tank Experiment

Hydrodynamic characteristics of a biplane-type otter board,equipped with nylon canvas of 2 mm in thickness was investigated through flume-tank experiment in this study.A series of predesigned structures with different gap-chord ratios G/c(0.75,0.90,1.05),stagger anglesθ(30°,45°,60°),and proportions of flexible area relative to the whole wing areaƒr(0,55%,65%,75%),at an aspect ratio of 2.0 and a camber ratio of 15%,were experimentally carried out.The results showed the solution referring to the usage of flexible canvas replacing part of rigid structure for the biplane-type otter board was efficient for the trawling in the middle or shallow water area.The improvement of lift and stability for the biplane-type otter board was concluded,and drag of the structure was reduced by 1.9%atƒr=55%.In addition,the coefficient of variation of the lift and drag coefficient at different current velocities were 2.69%and 2.28%,respectively,which was smaller than those at relatively large proportion of the flexible area.Compared with the other tested structures,the frame-type flexible structure with the gap-chord ratio of 0.9 and a stagger angle of 45°and the proportion of the flexible area of 55%,performed best,and its drag was reduced by 5.72%and lift increased by 4.8%,compared with the rigid biplane-type otter board at the angles of attack from 18°to 28°.

Immigrant Urban Housing and Socio-spatial Structure and Its Formation Mechanism:A Case Study of Shenzhen

Urban housing and socio-spatial attribute indicators are selected to identify housing and socio-spatial structure and its formation mechanism of Shenzhen.The following are the main conclusions.①Principal factors influencing the social area of Shenzhen include housing facilities,highly educated immigrants,migrant population,family structure,housing area and economic income level.②The socio-spatial structure which composed by six types of social areas shows obvious differentiation based on population mobility,housing,educational level and economic income level,forming a typical dual pattern of "urban society_-migrant worker society".③The formation of socio-spatial structure in Shenzhen results from natural conditions,economic development and institutional factors like the establishment of special economic zone,land system reform and urban planning.

鄂尔多斯盆地吴起地区延长组长6段储层特征研究

为深入研究吴起地区延长组长6段储层地质特征,通过开展各类分析测试,对研究区储层孔隙结构特征和流体可动性进行了定量表征,系统分析了不同成岩作用强度与物性之间的关系。结果表明:研究区长6段储层岩石类型为长石砂岩,填隙物以铁方解石和绿泥石为主,储层物性较差,孔隙类型以残余粒间孔为主。储层孔隙结构可分为Ⅰ类、Ⅱ类和Ⅲ类,对应的孔喉大小、孔喉连通性和可动流体饱和度依次变差。研究区长6段储层压实作用中等偏强,压实作用主要是减小储层的孔隙空间,但对储层渗流能力影响较小;碳酸盐矿物和黏土矿物胶结均降低了储层物性,但绿泥石膜的存在可以有效保存储集空间;而溶蚀作用对储层物性的改善作用较小。以上成果对鄂尔多斯盆地吴起地区延长组储层综合评价和开发方案制定具有一定理论指导价值。

交汇区水流结构对水温分布特征的影响机理

为分析交汇区复杂的水温分布规律及其受水流结构影响的机理,采用Fluent数值模拟软件,通过改变汇流角和汇流比,模拟了不同条件下交汇区的时均流场、紊动特性和水温分布,分析了各工况下交汇区水平面及断面水温分布特征(水温非均匀性指数)和水流结构特征参量(紊动能和涡量)间的关系,探究了不同水流结构对水温分布的影响机理。结果表明:水流剪切影响热掺混层的位置,二次环流影响热掺混层的形态;汇流角或汇流比越大,断面非均匀指数越小,水温掺混越快,热掺混层随剪切层位置的改变越靠近外岸壁(交汇口对侧壁面),热掺混层弯曲程度随二次环流强度增大而增大;紊动能及涡量与断面非均匀指数之间呈现良好的线性关系。

X波段双偏振雷达物理量时间—高度剖面的重构方法改进及应用研究

如何利用现有雷达体扫数据重构反射率或其它物理量的时间—高度剖面,提高雷达体扫垂直分辨率并使其适用于云微物理结构的分析,是近几年来雷达气象学的重点研究内容之一。本文基于分辨率更高的X波段双偏振雷达体扫数据,对目前最新的柱垂直廓线(Columnar Vertical Profile,简称CVP)重构算法从目标区范围的选取方面进行改进,使其能够应用于水平尺度较小的局地降水云以及发展演变迅速的对流云。结果显示:对于高原地区局地降水云个例,目标区选取5 km(径向范围)×10°(方位角范围)组成的较小扇形区域,与云雷达的对比显示,改进的CVP方法重构的基本反射率(ZH)垂直廓线体现了回波的垂直结构,尤其是中高层对流泡的结构特点,相应的时间—高度序列能够较好地反映回波顶高的变化以及中高层强度逐渐减弱、低层强度逐渐增加的特点;对于华北地区发展旺盛且局地水平不均匀的对流云个例,本文改进了原始的CVP重构目标区选取方法,对高、低仰角层采用变化的径向范围并调整插值参数,改进后重构的ZH垂直廓线有效避免了低层回波水平分布相对不均匀导致的重构分层结构,显示出高、低层回波特征以及不同阶段目标区云结构的转变。进一步对比改进前后CVP方法重构建立的各偏振量时间—高度序列,改进后准确显示了个例云系微物理特征及其随时间的变化,揭示了高原地区局地降水云中对流泡的形成及其播撒作用机制,华北地区对流云成熟阶段的各偏振量垂直分布特征及其演变。

宁夏东部杨柴生态修复区短期水氮添加对草本植物群落的影响

为研究短期水氮添加对杨柴生态修复区草本植物群落数量特征及其多样性的影响,在宁夏白芨滩国家级自然保护区杨柴生态修复区进行水氮添加试验,采用随机区组设计试验,每个区组设置4个水添加梯度(W0:未添加水分;W1:添加多年平均降水量的33%;W2:添加多年平均降水量的66%;W3:添加多年平均降水量的100%)和4个氮添加梯度(氮添加量分别为N0:未添加氮素;N1:5 g·m^(-2)·a^(-1);N2:10 g·m^(-2)·a^(-1);N3:20 g·m^(-2)·a^(-1))两两随机组合的16个水氮添加处理,共4个区组。结果表明:(1)不同水氮添加使植物群落结构发生了显著变化,与对照(W0N0)相比,草本层优势种狗尾草的重要值在中氮不施水(W0N2)、低水耦合高氮(W1N3)、中水不施氮(W2N0)、中水耦合中氮(W2N2)几种处理下达到最大值,其峰值为0.46,狗尾草集群分布明显,表明在中度水平的单一水、氮或中度水平的水氮耦合措施下群落聚集效应明显。(2)在不同水氮添加处理下,从不施氮(N0)到高氮水平(N3),草本植物群落物种丰富度、Shannon-Wiener多样性指数、Simpson优势度指数以及Pielou均匀度指数均随着氮水平的增加呈先增大后减小的趋势,且都在中水耦合低氮(W2N1)处理下有最大值。(3)氮添加对于生态修复区植物的物种丰富度、Simpson优势度指数以及Shannon-Wiener多样性指数均有显著影响(P<0.05)。综上,适量的水和氮添加更有利于生态修复区植被恢复,W2N1处理能够最好地改善杨柴生态修复区草本层植物群落物种多样性,从而有效地促进了沙漠化逆转进程。

鄂尔多斯盆地城华地区长3段储层微观孔隙结构及渗流特征

为了更加高效开发鄂尔多斯盆地城华地区长3段低渗油藏,利用铸体薄片观察、物性分析、高压压汞和油水相对渗透等实验分析,系统研究城华地区长3段储层微观孔隙结构差异及其对油水渗流特征的影响。结果表明:长3段储层岩性以长石砂岩为主,岩屑长石砂岩次之,填隙物以含铁碳酸盐岩及绿泥石为主;主要发育粒间孔和长石溶孔,面孔率低;颗粒间的接触关系主要为点-线接触和线-凹凸接触;喉道类型以片状、弯片状为主。根据孔隙度、渗透率、排驱压力及最大进汞饱和度等参数,将长3段储层孔喉类型由优到劣划分为三类。油水相渗特征也分为Ⅰ、Ⅱ、Ⅲ三类,其中Ⅰ类相对渗透率曲线交叉点较高,油相相对渗透率较高,储层渗流能力强;Ⅲ类相对渗透率曲线交叉点较低,油相相对渗透率也较低,储层渗流能力相对较弱;Ⅱ类介于两者之间,通过分析整合自吸法湿润性实验和油水两相渗流曲线,得出城华地区长3段储层一般在弱亲油性和亲水性之间。储层孔隙结构及储层润湿性是影响相渗特征的主要因素,且与相渗特征呈正相关。

城市绿地不同林分结构特征对土壤物理性质的影响

科学调整林分结构是解决城市绿地人工林土壤退化的重要途径。研究旨在为城市绿地合理经营提供理论依据。在山西省太原市森林公园中选取油松、榆树和刺槐人工纯林,分别设置20 m×20 m样地并以5 m间距均匀采集土壤样品,基于立木定位和每木检尺计算距土壤采样点不同半径处的林木株数、邻近木平均胸径等林分结构参数,采用Pearson相关和偏最小二乘回归分析法探讨林分结构因子对土壤物理性质的影响。结果表明,不同林分土壤物理性质存在一定差异,榆树林下土壤容重显著低于油松林和刺槐林,而土壤含水量、毛管持水量、毛管孔隙度、饱和持水量高于油松林和刺槐林。林分结构因子与土壤物理性质的相关系数在与立木冠幅均值大小近似的尺度上呈现最大值。通过Pearson相关性分析和偏最小二乘回归分析双重验证得出,榆树林的树高与土壤饱和持水量、毛管持水量、含水量存在极高的正相关性,相较于其他2个树种对改善土壤物理性质表现较优。

半干旱区复垦煤矿不同土地利用类型对土壤结构和水力学特性的影响

为探究半干旱区复垦煤矿土壤的水分特征,使复垦矿区土地得到更好的利用,选取复垦矿区还田、还草、还林、自然恢复等4种土地利用方式后的耕地、草地、林地、裸地等4种土地利用类型的土地,对土壤基本物理性质、水分特征曲线、非饱和导水率、水分扩散率进行研究。结果表明:复垦矿区内土壤为砂壤,林地孔隙度、含水量最高,容重和黏粒含量最低,耕地有机质含量最高,裸地有机质含量最低。裸地砂粒含量相对较高,耕地、草地、林地粉粒含量较高,可见通过还田、还草、还林这3种土地利用方式能改善矿区土壤的机械组成。Van-Genuchten(V-G)模型能够较好地拟合矿区土壤水分特征曲线,决定系数R2均大于0.99,土壤毛管重力水随水吸力增加显著下降,在2.5 kPa之前的吸力段持水能力呈现为耕地>草地>裸地>林地,随吸力增大,林地持水能力表现优于其他地类;释水过程主要出现在0~4.8 kPa吸力段,耕地释水能力最好,林地最差。土壤孔隙度与非饱和导水率呈现显著正相关,4种地类非饱和导水率林地>裸地>耕地>草地,林地的土壤结构性最好。土壤体积含水率与水分扩散率均符合D(θ)=Aexp(Bθ)的经验公式并呈指数曲线变化(A为当含水量为零时的土壤水分扩散能力;B为水分扩散率随含水量的变化速率),水分扩散率D(θ)随土壤体积含水率θ呈指数递增,决定系数R2均大于0.92,林地潜在传输水分的能力最好,裸地水分扩散率随含水率变化最快。研究结果可为半干旱区复垦煤矿的土地利用和生态修复提供理论及数据支持。

风沙区高等级公路设施与路基高度耦合对气流动力学和蚀积特征的影响

[目的]揭示风沙地区不同高度高等级公路附属设施对过境风沙流的扰动效应,分析不同高度与公路设施影响下的公路路面积沙程度,为公路工程设计和穿沙公路防护措施的制定提供理论依据。[方法]采用了计算流体力学(CFD)数值模拟方法,将普通公路作为对照,对比分析不同路基高度和公路设施组合对近地表过境气流的影响,并通过野外实测数据进行验证。[结果]公路设施显著影响了路基过境气流,导致公路形成减速区,不同高度路基产生多样性的水平气流速度变化。当路基高度在1~2 m之间时,气流扰动较弱,有助于断面输沙;当路基高度在3 m高度时,气流扰动较强,不利于断面输沙。气流穿过护栏和中央隔离带时,气流从护栏下方经过,风速增加,护栏背风侧最大风速的距离随着路基高度的增加呈现先增加再减小的变化趋势,路基高度在0,1,2,3 m时,最大风速距离分别为10,20,25,20 cm。随后在护栏背风侧与上层气流合并,尾流持续扩散,形成减速区,过境气流在该区域发生衰减,沙粒颗粒产生沉积,最高积沙高度11.5 cm,积沙宽度4~4.5 m。[结论]路基高度和公路附属设施是影响公路沿线沙害的主要因素。路基高度对气流到达路基上方的风速产生显著影响,而护栏和防眩网的存在可能在背风侧形成弱风区,从而导致公路上的沙堆积,存在潜在危险。

广西罗城地区某锡矿床矿石组构特征

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