科里奥利力对断层作用的统计研究

首先给出了分解到已知断层面法向和切向上的断层错动科里奥利应力(简称为科里奥利法向应力和切向应力)表达式,然后从哈佛大学矩心矩张量目录中选取主余震资料进行分析,按断层分类研究了科里奥利法向应力和主震震级与其最大余震震级差及主震地震矩与余震地震矩总和之差的折合矩震级间的关系.研究结果显示:地震断层错动过程中虽然产生了使断层两盘相互拉离(或挤压)的科里奥利法向应力,它降低(或增加)了断层错动时断层面上的摩擦阻力,但是应力量值太小(科里奥利法向应力估计最大不到0.1MPa,即不到一个大气压),不足以对断层错动及主震能量释放产生影响,从而影响余震的最大震级和总体水平.     

Pattern of abrupt climatic fluctuation in the East Asian Monsoon during the Last Glacial: Evidence from Chinese loess records

Records of two loess sections located in mid-eastern and western margins of the East Asian Monsoon area captured 20 Dansgaard-Oescher events and six Heinrich events. All these suggested that the climate in the East Asian Monsoon area fluctuated rapidly on millennial to century timescales during the whole Last Glacial. We found that these loess-based events of rapid climate fluctuations were generally synchronous with those of GRIP records, but that there were differences between the Shagou loess section in the west and the Wangguan loess section in the east: the former was more sensitive to climate change than the latter. Compared with earlier studies on loess records covering the Last Glacial from neighboring areas, we discovered that the magnitude of Dansgaard-Oeschger cycles decreased gradually from west to east and we suggest that it resulted from the combined effect of the Westerlies and the East Asian Monsoon.     

祁漫塔格东段晚三叠世花岗岩与流纹岩岩浆同源性:年代学、地球化学及Nd、Pb同位素制约

祁漫塔格位于东昆仑西段,对该地区晚三叠世火成岩的研究不仅有助于认识东昆仑造山带印支期构造—岩浆演化历史,而且为古特提斯洋俯冲时限及洋盆闭合时限提供约束。本次在克停哈尔南的二长花岗岩中获得了219.8±0.5 Ma的锆石U-Pb年龄,结合以往获得的年龄数据,可以确定该期火成岩为晚三叠世岩浆活动的产物。全岩地球化学分析结果显示,祁漫塔格东段晚三叠世火成岩为准铝到弱过铝质岩石,属高钾钙碱性系列,富集轻稀土和Rb、Th、K等大离子亲石元素,不同程度亏损Nb、Ta、P、Ti等高场强元素,具有明显的铕负异常,显示板块俯冲阶段的特征。花岗岩与流纹岩具有相似的Nd、Pb同位素组成,花岗岩ε_(Nd)(t)值介于-4.66～-4.53之间,亏损地幔模式年龄T_(DM2)为1363～1375 Ma,流纹岩ε_(Nd)(t)值为-4.63,T_(DM2)=1368 Ma。在n(~(143)Nd)/n(~(144)Nd)—n(~(206)Pb)/n(~(204)Pb)图解和Pb同位素组成图解中投影点均位于上地壳和EMII地幔端元附近。祁漫塔格东段晚三叠世花岗岩与流纹岩空间分布关系密切,形成时间相近,主、微量元素和Nd、Pb同位素特征方面都具有相似性或一致性,因此,笔者认为它们为同一时期、同一构造环境下的同源岩浆产物。结合区域资料和本文研究,初步分析认为东昆仑地区该时期处于板块俯冲阶段的活动大陆边缘弧环境,古特提斯洋尚未完全闭合。     

ScCO2-H2O作用下不同煤级煤化学结构变化的实验研究

超临界二氧化碳（ScCO₂）–H₂O–煤地球化学反应可造成煤物理结构和化学结构的改变,对煤层注CO₂增采甲烷的有效性尤为关键。为了探讨ScCO₂-H₂O-煤反应对不同变质程度煤化学结构的影响,选择3个不同煤化程度煤样,在自主研制的ScCO₂-H₂O-煤地球化学反应模拟实验装置中模拟1000m埋深条件下煤样与ScCO₂和去离子水反应240h,并对反应前后的煤样分别进行了X射线衍射和拉曼光谱实验,对比分析了反应前后煤样晶体结构和碳有序度的变化特征。测试结果表明：ScCO₂-H₂O反应破坏了煤的晶体完整性和碳有序度,改变了煤的大分子结构,且对低阶煤和中–高阶煤具有不同的影响,反应提高了低阶煤的平行定向程度,使其结构更加紧凑,减小了面网间距,而使中–高阶煤中无序单元增加,面网间距增大。该研究结果为CO₂-ECBM项目实施中ScCO₂-H₂O作用对煤储层吸附解吸特征和孔渗特征影响的研究奠定了微观尺度基础。     

21世纪中国主要粮食产区的空间格局特征

Grain production is an important issue for the national economy and the livelihood of the Chinese people. It serves as the foundation of national development and social stability. China is a major grain producer as well as a major grain consumer. The grai…     

Quantifying the impacts of climate change and land use on hydrological processes: A comparison between mountain and lowland agricultural watersheds

Mountain and lowland watersheds are two distinct geographical units with considerably different hydrological processes. Understanding their hydrological processes in the context of future climate change and land use scenarios is important for water resource management. This study investigated hydrological processes and their driving factors and eco-hydrological impacts for these two geographical units in the Xitiaoxi watershed, East China, and quantified their differences through hydrological modelling. Hydrological processes in 24 mountain watersheds and 143 lowland watersheds were simulated based on a raster-based Xin'anjiang model and a Nitrogen Dynamic Polder (NDP) model, respectively. These two models were calibrated and validated with an acceptable performance (Nash-Sutcliffe efficiency coefficients of 0.81 and 0.50, respectively) for simulating discharge for mountain watersheds and water level for lowland watersheds. Then, an Indicators of Hydrological Alteration (IHA) model was used to help quantify the alterations to the hydrological process and their resulting eco-hydrological impacts. Based on the validated models, scenario analysis was conducted to evaluate the impacts of climate and land use changes on the hydrological processes. The simulation results revealed that (a) climate change would cause a larger increase in annual runoff than that under land use scenario in the mountain watersheds, with variations of 19.9 and 10.5% for the 2050s, respectively. (b) Land use change was more responsible for the streamflow increment than climate change in the lowland watersheds, causing an annual runoff to increase by 27.4 and 16.2% for the 2050s, respectively. (c) Land use can enhance the response of streamflow to the climatic variation. (d) The above-mentioned hydrological variations were notable in flood and dry season in the mountain watersheds, and they were significant in rice season in the lowland watersheds. (e) Their resulting degradation of ecological diversity was more susceptible to future climate change in the two watersheds. This study demonstrated that mountain and lowland watersheds showed distinct differences in hydrological processes and their responses to climate and land use changes.     

2022年四川泸定MS6.8地震前地震活动与地球物理观测异常回顾与讨论

2022年9月5日四川泸定M_S6.8地震发生在2022年度全国地震重点危险区内,且震前作了较好的短期预测。本文回顾了中期(年度)和短期阶段地震活动和地球物理观测异常。①2022年度危险区确定的核心依据有川滇藏交界4级地震空区、危险区附近M_L≥3.5地震空区、跨断层形变趋势异常和重力场异常等,其中,川滇藏交界4级地震空区被2022年1月2日云南宁蒗M_S5.5地震打破具有中短期预测意义。②短期阶段,川滇藏交界4级地震空区经历了“打破—增强—平静”的演化过程,与1973年四川炉霍M_S7.6地震前高度相似,这可能与其发震构造相同、震源机制解一致和深部孕震环境相似有关。此外,还存在川滇地区震群和多个余震区准同步活动、巴塘显著震群等异常。地球物理观测方面,在2022年6月1日芦山M_S6.1和6月10日马尔康M_S6.0地震后,四川前兆异常无明显减少,而在7—8月显著增多,这可以作为强震后短期仍有可能再次发生强震的判定依据。新增异常主要分布在以三岔口(鲜水河断裂带、安宁河断裂带和龙门山断裂带交汇区,呈“Y”字形分布)为中心的300km范围内,这是震前短期地点预测的主要依据之一。③6.8级地震前形变中短期大幅度异常突出,且异常点均位于远场(距离6.8级地震震中130～300km范围内)。除礼州测距外,其余异常点均位于M_L3.5地震空区外围。形变异常出现的时间与M_L3.5地震空区打破后空区内部及边缘地震活动显著增强大体一致。④泸定6.8级地震发生在三岔口地区,该区及附近2015—2021年连续多年被确定为全国地震重点危险区,但均未发生预测地震,由此表明当前有效的强震年度(中期)时间预测依据少。     

赤峰撰山子花岗岩年代学、地球化学特征及其成岩动力学背景

撰山子角闪二长花岗岩位于华北克拉通与兴蒙造山带结合部位的中生代构造岩浆活动带,对其开展了主量元素、稀土和微量元素分析以及LA-ICP-MS锆石U-Pb定年等工作,目的在于精确厘定岩体的形成时代和研究其形成的动力学背景。结果表明：花岗岩的LA-ICP-MS锆石U-Pb谐和年龄为（245.8±3.1）Ma（MSWD=3.7,n=17）,属早三叠世。岩石地球化学成分特征显示为,其具有高硅（w（SiO₂）=71.68%~72.85%）、富碱（w（Na₂O+K₂O）=8.98%~9.20%）、高铝（w（Al₂O₃）=13.45%~13.77%）、低钙（w（CaO）=0.81%~0.99%）及低TFeO/MgO值（平均值为6.55）的特征,属高钾钙碱性、高分异I型弱铝质花岗岩;稀土配分曲线呈现向右倾斜的配分模式,Eu具有明显的亏损（δEu=0.66~0.68）,表明斜长石发生了明显的分离结晶作用;在微量元素原始地幔标准化图谱上呈现清晰的Th、U、La、P富集,Ba、Nb、Ti、Sr、Ta等相对亏损的特征。综合分析认为,撰山子角闪二长花岗岩主要形成于下地壳部分熔融作用,可能有少量的地幔组分加入,其形成于华北板块和西伯利亚板块最终拼合后的后碰撞/后造山伸展作用构造环境。     

华北北部中元古界洪水庄组物源和沉积环境分析

为探讨华北地区中元古界洪水庄组黑色泥页岩物源和沉积环境,采集了燕辽地区清河剖面洪水庄组样品,进行元素地球化学测试和分析.结果表明:洪水庄组沉积物来源不仅有陆源碎屑物质,还有海水沉积物贡献.Y/Ho和ΣREE交会图版分析认为海水沉积物来源占比为10％～20％.此外,稀土元素分布模式以及Ce和Eu异常表明沉积物来源有火山热...     

川东北元坝西部须家河组二段优质储层展布特征研究

川东北元坝地区须家河组二段致密砂岩气资源潜力巨大,但储量探明率低、测试效果差异大,主要原因之一是致密砂岩储层非均质性强、优质储层分布规律不清。本文充分利用测录井、岩心及相关分析化验等资料,在分砂组刻画沉积微相展布的基础上,开展了须二段沉积演化过程、储层特征及其分布研究。结果表明：（1）元坝西部须二段经历了辫状河三角洲-滨浅湖-辫状河三角洲演化过程,沉积控制了砂体规模、粒度和矿物成分的空间变化;（2）须二段砂岩类型多样,整体致密,为低孔、低渗储层;储层物性与砂岩粒度,长石、石英和方解石胶结物含量等因素密切相关,这些因素主要受沉积和后期成岩作用控制;（3）须二段发育块状中粒长石岩屑砂岩和交错层理中粒石英砂岩两类有利岩石相,前者自西北向东南逐渐减薄、呈条带状展布,后者呈不连续土豆状,主体分布于西南部地区。