2022—2023年四川泸定MS6.8、MS5.0和MS5.6地震序列的发震构造及成因

四川泸定2022年9月5日发生MS6.8强震, 随后10月22日和2023年1月26日又分别发生MS5.0和MS5.6强余震, 主震和两次强余震的震中相距仅几公里却有着截然不同的震源机制解, 因此, 探究三者的发震构造、联系及成因至关重要. 本研究利用国家地震台网记录到的这三次地震序列的连续波形数据及震相资料进行双差重定位, 并进一步采取CAP波形反演方法和P波初动极性反演方法获得研究区ML2.5+的79个余震震源机制解. 结果显示, 主破裂沿鲜水河断裂磨西段, 破裂彻底, 余震活动性不高. 沿主断裂分布的余震具有明显的分段特征, 断层近直立且西北浅东南深. 主震及磨西段大部分余震均为走滑机制, 是典型的印度—欧亚板块挤压旋转造成鲜水河走滑断裂带应力失稳触发的强震活动. 发生在贡嘎山地区的余震是MS6.8主震触发的震群活动, 震级水平不高, 分布弥散, 并没有触发与主断裂共轭的燕子沟、海螺沟和磨子沟次级断裂, 而是触发了与主断裂近平行的次级隐伏断裂——贡嘎山断裂. MS5.0和MS5.6两次强余震均发生在该次级隐伏断裂上, 断层倾角40°~50°且震源深度较浅. 贡嘎山地区拉张型地震活动明显不同于走滑型为主的鲜水河断裂带, 可能是印度—欧亚板块挤压旋转作用下贡嘎山快速隆升而地表快速剥离导致局部因重力卸载而垮塌造成的, MS6.8主震有明显的触发作用. 三次泸定强震的发生, 释放了磨西段及西侧贡嘎山地区部分应力, 但并未改变"Y"字形交汇区强震发生的可能性.     

亚洲高山区积雪物候时空动态及其对气候变化的响应

以亚洲高山区为研究区,在对2000—2020年逐日MODIS积雪产品进行去云处理的基础上提取了每一水文年的积雪日数（snow-covered days, SCD）、积雪开始日期（snow onset date, SOD）、积雪结束日期（snow end date, SED）和积雪持续日数（snow duration days, SDD）等积雪物候参数,并分析了积雪物候时空动态特征及其与气候变化的响应关系。结果表明：亚洲高山区积雪物候空间差异较大,并呈现出主要受海拔影响的垂直地带性分布规律。研究区SED主要集中在3—6月,在低海拔区SED出现在3月份及以前,而高海拔山区则推迟到6月份及以后;SOD主要集中在9—12月,高海拔山脉及高纬度地区的SOD出现较早,而低海拔区的SOD多出现在11月及以后。近20年,研究区SDD主要呈缩短趋势,在13.5%的区域呈显著缩短,而仅7.4%的区域为显著延长;SED主要呈提前趋势,在15.8%的区域显著提前,而仅8.8%的区域为显著推迟;SOD主要呈推迟趋势,在11.4%的区域表现为显著推迟,在8.2%的区域为显著提前。亚洲高山区积雪物候年际变化对气候变化的响应关系明显,积雪累积期气温是影响SOD年际变化的主导因子,而融雪期气温是影响SED年际变化的主导因子;气温的上升,导致了SOD的推迟、SED的提前和SDD的缩短。     

山西五台山和冀东迁安地区条带状铁矿的岩石化学特征及其地质意义

详细报道了五台山地区白峪里、柏枝岩和峨口(又名山羊坪铁矿)3个新太古代条带状铁矿床和冀东迁安地区条带状铁矿样品的岩石学和岩石化学特征,并与辽宁鞍山和山东韩旺以及国外同类矿床进行了对比。五台山地区和冀东迁安地区条带状铁矿的微量元素和稀土元素的含量和配分特征与国内外同类矿床十分一致:4个地区条带状铁矿样品均富集Th、U、La、Ce、P、Sm等元素,亏损K、Nb、Sr、Hf、Er、Ti等元素;稀土元素总量均较低,是太古宙海洋沉积特征之一,轻稀土元素轻微亏损,重稀土元素稍富集,具有明显的Eu的正异常,部分具有Y正异常。Y的异常通常代表了海水的特征,Eu的正异常指示了高温海底热液的特征,由此可判断铁硅质建造形成于热海水环境。五台山地区与条带状铁矿伴生的黄铁矿的δ34S值在零附近,表明其来源于地幔。由此可知所研究条带状铁矿床是幔源的火山喷发或火山喷气带来的硅铁质溶于海水后在特定条件下经化学沉积而成。     

NUMERICAL PREDICTION EXPERIMENT OF AN ADVECTION FOG IN NANLING MOUNTAIN AREA*

Now more comprehensive cloud microphysical processes have been included in advanced three-dimensional mesoscale meteorological model such as PSU/NCAR MM5 model,so the model can be used in the prediction of fog.In this paper,MM5 was utilized to simulate an advection fog occurring in Nanling Mountain area.The simulated results were compared with the facts obtained by detailed observation experiment.The results showed that the simulation was successful in the following aspects:(1)the formation and development of the fog;(2)the temporal variation of the maximum liquid water content;(3)the diffusion of the cold air,especially the temporal variation of the ground temperature;and (4)the uplift of the air and the formation and development of the low-lever inversion.Besides,we did some sensitivity numerical experiments and discussed the effects of the radiation,the release of condensation latent heat and the change of soil moisture and temperature on the formation and development of fog.The success of numerical simulation experiment of fog has proved that the numerical forecasting of fog is promising.     

五台山西南麓“龙泉关群”地层、构造特征及有关问题的讨论

根据造山带地层学地层划分原则,“龙泉关群”可划分为两个性质截然不同的地层单元:其一是“龙泉关构造岩层”,为构造地层单元;其二是“跑泉厂变沉积岩组”,属经典地层单元。前者经历了至少两期变形、变质作用,保留着走向近SN和近EW两组矿物拉伸线理以及角闪岩相和角闪岩相→绿片岩相退变质特征;后者仅发育有一组走向近SN矿物拉伸线理和一期绿片岩相变质作用。这表明:(1)“龙泉关群”实际上包含着两个世代不同的地层单元,应予解体。其中,“龙泉关构造岩层”形成于晚太古代末期,属于“阜平古陆块”刚性基底一部分;“跑泉厂变沉积岩组”的地层层位相当于“五台群”,是“阜平古陆块”西北陆缘带沉积,时代归属早元古代早、中期。(2)“龙泉关群”不是由一个统一的应力场同时形成的一套构造岩,因而不应将其作为一个大型韧性剪切带。(3)“龙泉关群”构成五台碰撞造山带前陆地区的活化基底和活化盖层两个大地构造相。“龙泉关群”的解体及其地层时代的重新厘定支持“板峪口组应归属滹沱群一部分”和“铁堡运动即为五台运动”的看法。     

ON THE DIVISION OF NORTH BOUNDARY OF SUBTROPICAL ZONE ACCORDING TO THE COMPOSITIONS AND PROPERTIES OF SOIL HUMUS

In this paper predecessorsˊ achievements about the division between subtropical zone and warm temperate zone on the south slope of Funiu Mountain are firstly summarized,and the cause why these viewpoints about the division are different also has been presented.Seven soil profiles at different heights above sea level are dug along the south slope of Funiu Mountain.Many compositions and properties of soil humus have been analyzed in laboratory.A comprehensive study has been made about the division according to the compositions and properties of soil humus with mathematical method.During the analysis process eitht indexes have been used,such as altitude,organic carbon,humic acid(HA),fulvic acid(FA),the ratio of humic acid and fulvic acid(HA/FA),two extinction coefficients(E4,E6), and their ratio (E4/E6).The result indicates that the boundary is at about 1000 meters above sea level.     

昆仑山口西8. 1级地震的地震活动特征

在回顾昆仑山口西8. 1级地震前的长期、中期的不同阶段不同程度的预测意见基础上,对该次地震前的地震活动进行了分析。结果表明, 该次巨大地震前存在地震条带、地震空区、地震活动增强区、象限性等空间异常及地震活动参数异常, 这些特征对巨大地震的研究与预测具有重要的参考作用。     

Intercomparison and validation of MODIS and GLASS leaf area index (LAI) products over mountain areas: A case study in southwestern China

The validation study of leaf area index (LAI) products over rugged surfaces not only gives additional insights into data quality of LAI products, but deepens understanding of uncertainties regarding land surface process models depended on LAI data over complex terrain. This study evaluated the performance of MODIS and GLASS LAI products using the intercomparison and direct validation methods over southwestern China. The spatio-temporal consistencies, such as the spatial distributions of LAI products and their statistical relationship as a function of topographic indices, time, and vegetation types, respectively, were investigated through intercomparison between MODIS and GLASS products during the period 2011–2013. The accuracies and change ranges of these two products were evaluated against available LAI reference maps over 10 sampling regions which standed for typical vegetation types and topographic gradients in southwestern China.The results show that GLASS LAI exhibits higher percentage of good quality data (i.e. successful retrievals) and smoother temporal profiles than MODIS LAI. The percentage of successful retrievals for MODIS and GLASS is vulnerable to topographic indices, especially to relief amplitude. Besides, the two products do not capture seasonal dynamics of crop, especially in spring over heterogeneously hilly regions. The yearly mean LAI differences between MODIS and GLASS are within ±0.5 for 64.70% of the total retrieval pixels over southwestern China. The spatial distribution of mean differences and temporal profiles of these two products are inclined to be dominated by vegetation types other than topographic indices. The spatial and temporal consistency of these two products is good over most area of grasses/cereal crops; however, it is poor for evergreen broadleaf forest. MODIS presents more reliable change range of LAI than GLASS through comparison with fine resolution reference maps over most of sampling regions. The accuracies of direct validation are obtained for GLASS LAI (r = 0.35, RMSE = 1.72, mean bias = −0.71) and MODIS LAI (r = 0.49, RMSE = 1.75, mean bias = −0.67). GLASS performs similarly to MODIS, but may be marginally inferior to MODIS based on our direct validation results. The validation experience demonstrates the necessity and importance of topographic consideration for LAI estimation over mountain areas. Considerable attention will be paid to the improvements of surface reflectance, retrieval algorithm and land cover types so as to enhance the quality of LAI products in topographically complex terrain.     

山西云顶山亚高山草甸群落生态分析

应用双向指示种分析法 (TWINSPAN )和除趋势对应分析 (DCA )等数量分析方法,对山西云顶山亚高山草甸生态关系进行了研究,将该草甸划分为5个群落类型,分别位于不同的海拔高度。分类结果很好地反映了植物群落类型及优势种的分布与环境因子之间的关系,并在DCA二维排序图上得到了较好的验证。DCA排序轴反映了海拔高度、放牧强度和群落土壤湿度的梯度变化,表明海拔高度和水热条件是影响植物群落变化的主要环境因子,物种多样性在群落类型分化中有重要作用,同时放牧对亚高山草甸演替过程的干扰明显。     

青海祁连山冻土区天然气水合物资源量的估算方法——以钻探区为例

祁连山冻土区天然气水合物DK-1、DK-2、DK-3、DK-4号钻孔揭示,该区天然气水合物及其异常主要产出于破碎岩层裂隙中和砂岩孔隙中,根据不同的赋存类型分别赋予具体地质含义,并运用体积法建立了2种产状天然气水合物资源量的计算方法。基于野外地质观测统计数据和室内分析测试结果,在钻探区约40×104m2的范围内,计算得到砂岩孔隙中的天然气水合物资源量约为6.24×104m3天然气,破碎岩层裂隙中的天然气水合物资源量约为88×104m3天然气,总的资源量约为94.2×104m3天然气。可以看出,钻探区中产于破碎岩层裂隙中的天然气水合物资源量是主体,这与钻探中肉眼观察的结果一致。