The concentration and isotopic composition of carbon in basaltic glasses from the Juan de Fuca Ridge, Pacific Ocean

The abundance and 13C/12C ratios of carbon were analyzed in basaltic glass from twenty locations along the Juan de Fuca Ridge using a 3-step combustion/extraction technique. Carbon released during the first two combustion steps at 400-500 degrees C and 600-650 degrees C is interpreted to be secondary, and only the carbon recovered during a final combustion step at approximately 1200 degrees C is thought to be indigenous to the samples. For carbon released at approximately 1200 degrees C, glasses analyzed as 1-2 mm chips contained 23-146 ppm C with delta 13C values of -4.8 to -9.3%, whereas samples crushed to 38-63 microns or 63-90 microns yielded 56-103 ppm C with delta 13C values of -6.1 to -9.2%. The concentrations and isotopic compositions of the primary carbon dissolved in the glasses and present in the vesicles are similar to those previously reported for other ocean-ridge basalts. The Juan de Fuca basaltic magmas were not in equilibrium with respect to carbon when they erupted and quenched on the sea floor. Evidence of disequilibrium includes (1) a large range of carbon contents among glasses collected at similar depths, (2) a highly variable calculated carbon isotopic fractionation between melt and vapor determined by comparing crushed and uncrushed splits of the same sample, and (3) a lack of correlation between vesicle abundance, carbon concentration, and depth of eruption. Variations in carbon concentration and delta 13C ratios along the ridge do not correlate with major element chemistry. The observed relationship between carbon concentrations and delta 13C values may be explained by late-stage, variable degrees of open-system (Rayleigh-like) degassing.     

Species sensitivity distributions: data and model choice

Species sensitivity distributions (SSDs) are increasingly incorporated into ecological risk assessment procedures. Although these new techniques offer a more transparent approach to risk assessment they demand more and superior quality data. Issues of data quantity and quality are especially important for marine datasets that tend to be smaller (and have fewer standard test methods) when compared with freshwater data. An additional source of uncertainty when using SSDs is appropriate selection from the range of methods used in their construction. We show through examples the influence of data quantity, data quality, and choice of model. We then show how regulatory decisions may be affected by these factors.     

GPS在我国地震研究中的应用现状与展望

GPS应用已成为现代地震研究领域中的一个重要组成部分,已经深入到我国地震研究领域中的各个学科.本文介绍了GPS在形变、测震、电磁、地震预警和地震观测仪器授时中的应用现状,并对GPS在地震研究中应用的发展趋势进行了展望.     

2022年1月8日青海门源6.9级地震短临异常跟踪分析

2022年1月8日青海门源县发生6.9级地震,此次地震前青海地区出现了大量地球物理观测异常。2021年10月下旬青海地区出现地磁垂直强度极化高值异常,10月27日异常台站最多,并在门源-祁连至兴海地区形成一个面积约为6.6×10⁴km²的高值异常区;此外,2021年7—11月青海地区8项地下流体观测数据出现准同步异常变化。结合青海及周边地区历史震例的分析结果,认为2021年11月23日至2022年1月23日,青海西北部地磁垂直强度极化高值区内可能发生5.6～6.4级地震。门源6.9级地震发生在地磁垂直强度极化异常出现后的73天,震中位于预测区的边缘,地震的发生时间和地点与预测意见一致,但震级超出预测意见上限值0.5级。此次地震前基于地球物理观测地震预测指标体系开展的短临异常跟踪分析过程,对中国大陆西部地震预报工作具有一定的参考意义。     

自然风景区雷电灾害风险评估方法研究

雷电灾害已日益成为影响人类经济社会发展的严重灾害之一。基于信息扩散理论建立雷电灾害风险评估模型,对江苏省2008—2019年雷电灾害事故进行分析计算。结果表明：江苏省雷电灾害事故多集中于320次·a^-1内,约1.9 a一遇,而发生880次·a^-1以上的概率较小,约38.2 a一次;人身伤亡风险主要集中在12人·a^-1内,约1.8 a一遇,大于30人·a^-1的伤亡次数则约14.1 a发生一次;经济损失风险值为650万元·a^-1的累积发生概率为58.62%,而2 250万元·a^-1的发生概率极低,仅为1.84%。定量化的计算分析数据可使人们对雷电灾害事故有更深入的了解,并为相关政府部门制定防灾减灾决策提供一定的科学依据。

     

基于航测的珠三角气溶胶垂直分布及活化特性

2017年9月14—27日在珠江三角洲地区开展了6个架次飞机观测试验。利用飞行获取的气溶胶、云凝结核、云滴及常规气象探头观测资料,结合天气形势、气象条件及气团后向轨迹分析,研究了珠江三角洲地区深圳气溶胶数浓度及其谱的垂直分布特征,配合不同过饱和度条件下云凝结核浓度观测,分析了气溶胶活化特性。结果表明：在不同天气条件下,深圳低层气溶胶数浓度变化范围为500~9000 cm-3;边界层内气溶胶分布相对均匀,谱型随高度变化与气象条件相关。将6个架次气溶胶观测资料根据数浓度及谱型分为3种类型：类型Ⅰ为海洋型气溶胶,数浓度小,粒子尺度大,谱型呈双峰分布;类型Ⅲ为大陆型气溶胶,数浓度高,粒子尺度小,谱宽较宽且呈三峰分布;类型Ⅱ为海洋大陆影响型气溶胶,即受海洋和大陆共同影响,数浓度低于类型Ⅲ高于类型Ⅰ,谱型为双峰分布。拟合了包含海洋型及大陆型气溶胶的3个架次近地面云凝结核活化谱,计算了气溶胶在不同过饱和度条件下的活化效率。     

胶东半岛及两侧海域尾波Q值分析

根据单次散射（Aki）模型,利用2003年至今山东台网记录的26次2．9级以上地震的数字化地震波,研究并探讨了胶东半岛及两侧海域平均尾波Q值,在1～18Hz的频率域范围内,Q值与频率的依赖关系为：胶东北部海域Qc=（313士42）,f^（0.653±0.145）,胶东内陆Qc=（319±88）f^（0.649±0.145）,黄海海域Qc=（259±60）f^（0.757±0.277）,与国内其他区域尾波Q值研究结果相比,本区域Qc为高值、对频率低依赖性区域。可能与本研究区内构造活动弱、地震活动水平低有关。     

面向复杂山地的机载LiDAR与无人机影像融合应用

本文针对LiDAR点云与无人机影像数据特征的优缺点,利用LiDAR点云与无人机DOM影像融合,将影像数据光谱信息赋给LiDAR点云数据,使其不仅具备精准的空问结构信息,还能得到清晰的纹理信息.为验证融合数据应用的可行性与数据提取的准确性,对融合前后的点云数据进行地面点提取与DEM构建.试验表明:将无人机影像的光谱信息赋...