ENVIRONMENTAL RESPONSE OF THE PERMIAN VOLCANISM IN LUCAOGOU FORMATION IN JIMSAR SAG,JUNGGAR BASIN,NORTHWEST CHINA

The lithological features, the types of organic matter and its occurrence and carbon and oxygen isotopic value were clarified by combining core observation, thin slice authentication, X ray diffraction analysis, kerogen type identification and carbon and oxygen isotope analysis. The characteristic of strata, the distribution of volcanoes of Junggar Basin were also taken into consideration. A comprehensive analysis was conducted to evaluate environmental response of volcanism in Lucaogou formation in Jimsar sag. The results show that rocks is a mixed sedimentation of effusive rock and carbonate rocks, volcanic materials is widely developed in Lucaogou formation and origins from the edge of sag or distant source volcano activity. Organic matter is predominantly unstructural algae and asphaltene. The carbon isotopic value of carbonates ranges between 6.8‰ and 9.7‰ with an average of 8.3‰, featured in high positive excursions, while oxygen isotopic value varies from -11.9‰ to -4.3‰ with an average of -6.2‰. During the period of volcanic activity, the volcanic material released high amounts of nutrient to the lake basin, which is beneficial to the algae and other organic organisms. In the poor oxygen and calm water environments, the organic matter is distributed in the laminar algal and the carbon isotope value is high positive drift. During the intermittent period of volcanic activity, the lake level decreased and the lake bottom water changed to the oxygen-enriched environments. The organic matter is locally enriched or dispersed in local layers, and the carbon isotope values decreased slightly. The frequent volcanic activity promoted the organism boom, which lead carbon isotope value to have high positive characteristics and change trends.     

能谱CT在急性肺栓塞诊断及肺血流灌注变化评估中的应用

目的：探讨能谱CT对急性肺栓塞诊断及肺血流灌注变化评估的应用价值。方法：回顾性分析2017年11月至2019年7月43例怀疑急性肺栓塞的影像资料,所有疑似急性肺栓塞患者行能谱增强扫描,原始数据图像在工作站重建肺动脉血管图像及碘基物质图。观察并记录肺动脉栓子的位置、数目;分析碘基物质图中肺内血流灌注降低区的位置及数目,并测量肺内血流灌注降低区的碘基值及CT值,同时测量同层面或邻近层面正常肺实质的碘基值及CT值。混合能量图像与最佳单能量图像对栓子检出的数量比较采用卡方检验,血流灌注减低区与正常区域碘基值、CT值比较采用两样本秩和检验。结果：明确诊断肺动脉栓塞12例,采用混合能量图像观察发现栓子256个,其中中心型栓子（肺动脉主干、肺叶栓子）22个,外周型（肺段、肺亚段栓子）234个;完全闭塞型栓子58个,非完全闭塞型栓子198个。采用最佳单能量图像观察发现栓子273个,其中中心型栓子（肺动脉主干、肺叶栓子）22个,外周型（肺段、肺亚段栓子）251个;完全闭塞型栓子74个,非完全闭塞型栓子199个。最佳单能量图像在诊断外周型及完全闭塞型栓子较混合能量图像能增加检出数量,但两组比较差异无统计学意义（P>0.05）。肺内血流灌注减低区42处,血流灌注减低区（（2.70±1.81）100μg/mm³、（-829±45.94）HU）与正常区域肺野（（17.78±3.29）100μg/mm³、（-741±34.34）HU）碘基值、CT值比较,差异有统计学意（P<0.05）。结论：能谱CT对肺栓塞能进行定性和定位诊断,碘基物质图能够评价肺血流灌注变化,为评估肺栓塞病情提供信息。     

回填土不确定性对场地地震反应的影响

选取某核电场地控制性钻孔的厚度、剪切波速、密度等实际勘探数据,通过改变回填土剪切波速,分析了回填土不确定性对场地地震动参数的影响。研究结果表明:在回填土层厚度不变和模型总厚度不变的情况下,地表的水平向峰值加速度随着回填土剪切波速的增大而减小,但水平向峰值加速度增幅逐渐减小;回填土剪切波速到达一定的波速就不再影响地表水平峰值加速度;随着回填土剪切波速的增加,整个反应谱的谱值都普遍减小。     

近场地震下竖向刚度不同的混合结构动力性能分析

近场地震的动力特性明显不同于远场地震,因此有必要对结构在近场地震作用下的动力性能展开研究。以上部钢结构-下部混凝土结构这类竖向刚度不同的加层混合结构为研究对象,对其在近场脉冲型地震、近场无脉冲型地震及远场地震作用下的动力响应进行研究。结果表明:在多遇、设防、罕遇地震作用下,近场脉冲型地震会使结构的层间位移角、层间剪力、加速度等动力响应均放大并出现超限的情况,而且都比罕遇地震作用下结构的响应增大更明显;在进行近场区加层混合框架结构的设计和建设时,近场脉冲效应会使结构存在不满足规范的情况,有必要对竖向刚度不同的加层混合结构在近场区的适用性进行深入研究。     

Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface

Changes in streamflow and water table elevation influence oxidation–reduction (redox) conditions near river–aquifer interfaces, with potentially important consequences for solute fluxes and biogeochemical reaction rates. Although continuous measurements of groundwater chemistry can be arduous, in situ sensors reveal chemistry dynamics across a wide range of timescales. We monitored redox potential in an aquifer adjacent to a tidal river and used spectral and wavelet analyses to link redox responses to hydrologic perturbations within the bed and banks. Storms perturb redox potential within both the bed and banks over timescales of days to weeks. Tides drive semidiurnal oscillations in redox potential within the streambed that are absent in the banks. Wavelet analysis shows that tidal redox oscillations in the bed are greatest during late summer (wavelet magnitude of 5.62 mV) when river stage fluctuations are on the order of 70 cm and microbial activity is relatively high. Tidal redox oscillations diminish during the winter (wavelet magnitude of 2.73 mV) when river stage fluctuations are smaller (on the order of 50 cm) and microbial activity is presumably low. Although traditional geochemical observations are often limited to summer baseflow conditions, in situ redox sensing provides continuous, high‐resolution chemical characterization of the subsurface, revealing transport and reaction processes across spatial and temporal scales in aquifers.     

山西地区远震P波到时残差分布

收集2008—2016年山西地震台网记录的震中距30°—90°范围内1 253个远震事件波形,拾取7 600余条高质量P波初至到时,使用IASP91模型计算相对到时残差,分析残差水平分布特征,结果显示:①以山西地区中部的山西断裂带为界,西部地震台站记录的P波初至主要表现为早到时,东部位于大同火山区的地震台站记录则主要表现为晚到时;②位于山西断裂带内部的地震台站记录的P波初至主要表现为早到时,残差水平显著低于西部地震台站;③研究区P波到时整体呈现自西向东逐渐由早到晚的分布特征。推测山西断裂带西部地区下方可能存在高速异常结构,山西断裂带内部及大同火山区下方可能存在低速异常结构。     

Analytical solution of seismic response of base-isolated structure with supplemental inerter

Closed-form solutions are derived for the modal characteristics and seismic response of a base-isolated structure equipped with additional inerters. By simplifying the structure-isolator-inerter system in terms of the two-degree-of-freedom (2DOF) model, the modal frequencies, mode shapes, damping ratios, and participation factors of the system are derived. Consequently, analytical seismic response solutions are formulated by the modal superposition method. Utilizing these analytical solutions, an extensive parametric study has been carried out to investigate the effect of supplement inerters on both the modal characteristics and seismic response of the structure-isolator-inerter system. There is a critical inertance leading to the zero second modal participation factor (ie, the disappearance of the second modal response). The associated critical inertance ratio is derived in closed form as well. Moreover, it is observed that the reduction of deformation of isolators by increasing the inertance may be offset by the increase in relative displacements of the superstructure. To circumvent this adverse effect, an optimal range of inertance is identified whereby both the deformation of isolators and the relative displacement of the superstructure are mitigated concurrently.     

Conditional spectrum bidirectional record selection for risk assessment of 3D structures using scalar and vector IMs

Several proposals are explored for the hazard and intensity measure (IM) consistent selection of bidirectional ground motions to assess the performance of 3D structural models. Recent studies have shown the necessity of selecting records that thoroughly represent the seismicity at the site of interest, as well as the usefulness of efficient IMs capable of estimating the response of buildings with low scatter. However, the advances realized are mostly geared towards the structural analysis of 2D models. Few are the combined record, and IM selection approaches suggested expressly for nonlinear dynamic analysis of 3D structural models, especially when plan asymmetry and torsion sensitivity come into play. Conditional spectrum selection is leveraged and expanded here to offer a suite of approaches based on both scalar and vector IMs that convey information from two orthogonal horizontal components of the ground motion. Applications on multiple 3D building models highlight the importance of (a) employing the same IM for both record selection and response assessment and (b) maintaining hazard consistency in both horizontal components, when using either a scalar or a vector IM. All tested approaches that respect these conditions can be viable, yet the one based on the geometric mean of multiple spectral ordinates from both components over a period range seems to hold the most promise for general use.     

安徽地区震源参数的相关性研究

基于安徽数字地震台网2010年1月至2017年12月记录到的ML2.5~5.0级地震,根据中小地震震源参数测定原理,利用多台多地震联合反演Atkinson方法和Moya方法分别计算了安徽地区地壳平均非弹性衰减因子Q值和安徽24个省属专业地震的台站场地。在此基础上,运用遗传算法求得安徽地区96个地震事件的震源谱参数,进而根据Brune中小地震圆盘模型计算其拐角频率、地震矩、应力降、矩震级、震源尺度等震源参数,并分析其特征及相互之间的关系。研究结果表明:安徽地区中小地震的ML震级与其他震源参数之间存在一定相关关系,而地震矩M0与应力降Δσ、震源尺度r和拐角频率fc之间并未表现出明显的相关关系。