3-D velocity structure of P wave in the upper mantle beneath southwestern China and its adjacent areas

3-D velocity structure of P wave in the upper mantle beneath southwestern China and its adjacent areas (10°N [similar to] 36°N, 70°E [similar to] 110°E) down to the depth of 400 km has been studied by using 80 974 P-wave first arrival times recorded at 165 stations from 7 053 events both within the studying areas, selected from the ISC bulletin and the Bulletin of China and NEIC fundamental seismic network. With a resolution of grid spacing of 2°×2°, the velocity heterogeneity on the horizontal profile is obvious though it attenuates with the depth increasing. On the vertical profiles of velocity along the latitude of 16°N and 24°N, the collision and extrusion of India plate to Eurasia plate is displayed, and a remarkable velocity difference between India plate and Eurasia plate is shown. In the vertical profile along the longitude of 90°E, the subducting of India plate northward beneath Eurasia plate (Tibet plateau) is also obvious. On the horizontal profile at the depth of 90 km, a slow velocity stripe from Myitkyina, Myanmar to Donghai, Vietnam seems to be related to Honghe fault belt. An illustration method of describing the resolution more directly and exactly has been proposed and utilized in this paper.

Influence of lithospheric thickness distribution on oil and gas basins,China seas and adjacent areas

The distribution of oil and gas resources is intricately connected to the underlying structure of the lithosphere.Therefore,investigating the characteristics of lithospheric thickness and its correlation with oil and gas basins is highly important.This research utilizes recently enhanced geological–geophysical data,including topographic,geoid,rock layer thickness,variable rock layer density,and interface depth data.Employing the principles of lithospheric isostasy and heat conduction,we compute the laterally varying lithospheric thickness in the China seas and adjacent areas.From these results,two pivotal parameters for different types of oil and gas basins were statistically analyzed:the minimum lithospheric thickness and the relative fluctuation in lithospheric thickness.A semiquantitative analysis was used to explore the connection between these parameters and the hydrocarbon abundance within the oil and gas basins.This study unveils distinct variations in lithospheric thickness among basins,with oil and gas rich basins exhibiting a thicker lithosphere in the superimposed basins of central China and a thinner lithosphere in the rift basins of eastern China.Notably,the relative fluctuations in lithospheric thickness in basins demonstrate significant disparities:basins rich in oil and gas often exhibit greater thickness fluctuations.Additionally,in the offshore basins of China,a conspicuous negative linear correlation is observed between the minimum lithospheric thickness and the relative fluctuation in lithospheric thickness.This study posits that deep-seated thermal upwelling results in lithospheric undulations and extensional thinning in oil and gas basins.Concurrently,sustained deep-seated heat influences sedimentary materials in basins,creating favorable conditions for oil and gas generation.The insights derived from this study contribute to a quantitative understanding of the intricate relationships between deep lithospheric structures and oil and gas basins.These findings provide valuable guidance for future oil and gas exploration in the studied areas.

Influence of the Moho surface distribution on the oil and gas basins in China seas and adjacent areas

Owing to the strategic significance of national oil and gas resources,their exploration and production must be prioritized in China.Oil and gas resources are closely related to deep crustal structures,and Moho characteristics influence oil and gas distribution.Therefore,it is important to study the relationship between the variation of the Moho surface depth undulation and hydrocarbon basins for the future prediction of their locations.The Moho depth in the study area can be inverted using the Moho depth control information,the Moho gravity anomaly,and the variable density distribution calculated by the infinite plate.Based on these results,the influences of Moho characteristics on petroleum basins were studied.We found that the Moho surface depth undulation deviation and crustal thickness undulation deviation in the hydrocarbon-rich basins are large,and the horizontal gradient deviation of the Moho surface shows a positive linear relationship with oil and gas resources in the basin.The oil-bearing mechanism of the Moho basin is further discussed herein.The Moho uplift area and the slope zone correspond to the distribution of oil and gas fields.The tensile stress produced by the Moho uplift can form tensile fractures or cause tensile fractures on the surface,further developing into a fault or depression basin that receives deposits.The organic matter can become oil and natural gas under suitable chemical and structural conditions.Under the action of groundwater or other dynamic forces,oil and natural gas are gradually transported to the uplift or the buried hill in the depression zone,and oil and gas fields are formed under the condition of good caprock.The research results can provide new insights into the relationship between deep structures and oil and gas basins as well as assist in the strategic planning of oil and gas exploration activities.

Discussion on the dextral movement and its effect in continental China and adjacent areas since Cenozoic

Continental China has moved dextral Eastward since Cenozoic time,driven by the collision of the Indian with the Eurasian plate.Evidence for this comes from landscape evolution,the distribution of earthquake epicenters,Cenozoic sedimentary and volcanic rocks,and the measurement of GPS velocity vectors,the distribntion of crustal stress,paleomagnetic data,and deep mantle structure,among others.This movement commenced around 40 Ma,coupled with thickened lithosphere and widespread stress release along strikeslip faults that bound the continental Chinese block.Because of continued Northward subduction of the Indian plate,manifestation of the dextral movement has intensified since 25 Ma.Far-reaching effects include extensive strike-slip movement on the Tan-Lu fault in Eastern China,formation of the Dabie ultrahigh pressure metamorphic terrane,extensive thrust faults in East China,delamination and thickening of the lithosphere of South China,a possible tectonic doubling of the Middle-Lower Yangtze Valley metallogenic belt,and the formation of the Japan,Huanghai (East China),and South China Sea.

A POSSIBLE IMPACT OF EL NINO MODOKI ON SEA SURFACE TEMPERATURE OF CHINA'S OFFSHORE AND ITS ADJACENT REGIONS

El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field.

The Mesozoic Basin-Mountain Coupling Process of the Southern East China Sea Shelf Basin and its Adjacent Land Area

Basin-mountain coupling is a key issue for basin formation and evolution. The analysis of basin-mountain coupling process, as well as quantitative or semiquantitative restoration of prototype basin and the evolution of continental margin, can be used to interpret the geological process of basin-range conversion and reconstruct early prototype basins, which is a difficult and leadin~ scientific oroblem of basin research.

Geological Characteristics of Epithermal Ore Concentrated Areas and Epithermal Ore Deposits in China

The epithermal ore concentrated area is located in Southwestern China. We systematically study the regional geological characteristics such as the basement of Proterozoic, the capping bed, Moho, geothermal feature and tectonics, and discuss the relationship between distributed characteristics of the epithermal ore deposits and ore control factors in this paper. It is concluded that the conditions, under which the epithermal ore deposits form, are huge thick basement of Proterozoic, long time and wide scope developed capping bed and weak magmatic activity. The basement of Proterozoic that enriches volcanic matters and carbon and the carbonaceous bearing and paleo pool bearing capping bed provides main ore source. The large and deep faults and paleopool accordance with gravity anomaly gradient control the distribution of epithermal ore deposits. The lithologic assembles of microclastic rocks and carbonate rocks in the capping bed provide spaces of ore precipitation and create conditions of ore precipitation. The coincidence of many geological factors above forms the epithermal ore concentrated area.

DECOLLEMENT STRUCTURE AND METALLOGENIC PROGNOSIS FOR BURIED URANIUM DEPOSITS OF EAST HUNAN AND ITS ADJACENT AREA,CHINA

East Hunan and its adjacent area is defined as an intraplate orogenic zone with help of new theory of geology and multi-discipline research. The evolutionary stages, deep structrue, geological feature, rotation strain and metallogeny of NW-striking transfer fault zone are also discussed. NE-trending strike-slip fault zone, as a whole, entered action during Pacific movement and underwent 3 stages: the strike-slip shear, the pull-apart extension and the’ compressive thrust. The aurthors studied macro-and microscopic features of strike-slip fault and its control of uranium mineralization at Jinguangchung deposit by means of modern structure analysis, micro-submicroscopic investigation and geophysical measurement.

Effects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China

The effects of selected land management practices （cross-sloping tillage, ridge culture, organic manure, and straw mulch） on soil water conservation in a southwestern mountainous area, China, were studied during November 2002 to November 2004. The experimental field is divided into three parts based on soil layer depths, 0-60 cm （part Ⅰ）, 0-40 cm （part Ⅱ）, and 0- 20 cm （part Ⅲ）, and they all had the same slope azimuth （SE）, slope （10°）, and slope type （linear）. The experimental plots were subjected to the following treatments： cross-sloping tillage （CST）; cross-sloping tillage with organic manure （CST/ OM）; cross-sloping tillage with straw mulch （CST/SM）; contour ridge culture （CRC）; contour ridge culture with organic manure （CRC/OM）; and contour ridge culture with straw mulch （CRC/SM）, to identify the effects of management practices on soil water. Water contents were determined for soil samples collected, using a 2.2 cm diameter manual probe. Soil water was monitored once every five days from Nov. 20, 2002 to Nov. 20, 2004. The results indicated that, in the study stages, an integration of rainfall, evaporative losses, and crop transcription controlled the basic tendencies of profile （mean） soil water, while land management practices, to a certain extent, only modified its amount, distribution, and routing. Moreover, these modifications also mainly focused on the first 20 cm depth of topsoil layer. When each management practice was compared with control treatment, season changes of profile （mean） soil water were pronounced, while interannual changes among them were not significant. More comparisons indicated that, in the study stages, contour ridge culture had better effects than cross-sloping tillage. And under the same tillage, the combination of organic manure could achieve more than straw mulch. These management practices should be recommended considering the effectiveness of soil and water management techniques in the southwestern mountainous area, China.

A study on zooplankton distribution patterns and indicator species in Kuroshio upstream area and adjacent East China Sea

On the basis of the data of zooplankton biomass and three major taxa—— Copepoda, Chaetognatha andSiphonophora of May-June 1986, July-August and December 1987, the distributional patterns and the indicator species of zooplankton in the Kuroshio and adjacent waters of the East China Sea are preliminarily studied. The results are as follows:The horizontal distribution of zooplankton biomass and the abundance of copepods, chaetognaths and siphonophores arecurred in the continent area northwest of Taiwan and the south-centre section of the East China Sea continent, which are the mix front of different waters. Zooplankton in the water area inside of Ryukyu Islands presented low abundance and high diversity. There are clear seasonal variations in zooplankton biomass and abundance in the study area. The strength or weakness of different water masses and fronts is the basic reason for the variations of zooplankton biomass and abundance.The species composition of zooplankton in the study area is complex and varies, however, the tropic oceanic species predominates overwhelmingly. The distribution of different ecotype species evidences the distribution of different water masses and the state of mixture. The indicator species of each water mass are listed in the paper so as to provide grounds for the variation of currents in the Kuroshio area.The temperature and salinity of sea water are important factors affecting zooplankton distribution, composition and diversity , however the role of salinity is major. With the replacement of one season by another, the correlative levels of temperature and salinity to various zooplankton taxa are more or less significant.

Study of radioactive status in the Zhujiang Estuary and adjacent sea area in South China Sea (SCS)

Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. radioactivity, total β radioactivity, artificial radioactive 90Srand 157Cs, and factors inflencing the distribution and the content of U in seawater are studied.The mainly radioactive pollution substances and their sources in the sea area are studied by γ spectra obtained from sediment in the sea area. The results show that the main radioactivity substances are natural radioactivity U,Th series and 40K. which were produced by the modern industry and transported into the sea through the main current of the Zhujiang River.

THE PERMIAN SYSTEM OF THE NUJIANG—LANCANGJIANG—JINSHAJIANG AREA, SOUTHWESTERN CHINA

Permian system is one of the best developed systems in Sanjiang area. In Yidun\|Zhongdian and in Zhiso\|Muli, The Lower Permian is clastics\|carbonates\|volcanics with interbeds of siliceous sediments, Whereas the Upper Permian is composed of lower part of basic volcanics and upper part of clastics\|carbonates with a total thickness of 1000～4000 meters .In Zhongzha (Batang)\|Jingping region, It is mainly carbonates of 217～1320 meters thick, But in Jingping proper, there occur about 5000 meters thick basalts of early late Permian . From Batang to Benzinan along the Jinshajiang river , the lower Permian is clastics\|volcanics\|carbonates formation with interbeds of siliceous sediments and spilite formation; Whereas the Upper Permian is clastics with volcanic interbeds; The total thickness being 3700 to 7100 meters. In Jiangda—Mangco (Mangkang), It is clastic\|carbonate\|volcanic formation of 1100 to 2400 meters . In Tuoba (Qamdo)—Haitong (Mankang)—Ximi (Mujiang ), It is mainly clastics\|carbonates formation , the Upper Permian being coal\|bearing clastics sequence and the total thickness being 700～2500 meters ,In Zhado—Zhasuosuo (Mangkang)—Deqing—Qinggu—Qinghong, It is clastic\|carbonate\|volcanic formation, locally with coal\|bearing clastics of Upper Permian and the total thickness of mainly carbonate formation and clastic formation with coal\|bearing clastic formation of Uppermian, is 800 to 2000 meters. In the whole area , the Permian strata were slightly metamorphosed, locally more intensively metamorphosed up to amphibolite facies. The fossils found belong to fusulinids, coral, brachiopods,ammonite,bivalve, gastropods, bryozoa,foraminifera, trilobite, algae ,porifera (sponge), and continental plant . Besides the Gondwana cold\|water type components of brachiopods found in Baoshan, the fossils belong mainly to Cathaysian biota, especially to South China type. In some places such as Mangkang, Guxue (Dewong), to South China type. In some places such as Mangkang, Guxue (Dewong), and Wachang (Muli), the resedimented Late Carboniferous fusulinid fossils can be found in the clastic limestone of Lower Permian, and the Early Permian or even Middle to Late Carboniferous fusulinid fossils found in Upper Permian classic limestone. All these suggest the resedimentation of biolimestone blocks or fragments related to fault\|volcanism .On the section of Tongba (Muli), the permian is continuous graded upwards into the Triassic, with a transitional zone of fossil.

A New Discovery of Deep-Water Benthic Organisms from the Southwestern Dongsha Area,South China Sea

Dongsha waters are poorly studied for gas hydrates. Previous multi-channel seismic reflection and Chirp sub- bottom profiles show that numerous submarine mounds stand up to 100 m high above the seafloor over the continental slope of the SW Dongsha Island in northern margin of the South China Sea （SCS）. These mounds are characterized by hardened seabed, seafloor gas venting and folded structures, which implies the existence of active mud volcanoes. This work aims to confirm this speculation by seafloor sample dredging and to explore the potential of gas hydrates.

山坝结构与族际共生:历史时期西南边疆民族交往交流交融的文化生态学考察

历史上西南边疆地区不同的经济文化类型和民族分布格局,反映了山坝结构形态下多元民族互嵌共生的社会结构特点。在山坝结构的空间单位中,各民族既发展出适应各自生境的经济文化类型,又通过不同群体的交流互动形成既相互区别又相互联系的社会文化系统。以山坝结构为研究对象,不仅能够较为清晰地呈现“人地关系”下西南边疆各民族交往互动的空间特征,而且还可以从民族共生的整体逻辑来认识西南边疆民族社会历史发展的多样性以及边疆各民族交往交流交融历史演进的区域特性。在认识论层面,相关研究或许能够在传统认知基础上,为当下中华民族共同体形成路径等议题提供一种新的观察视角。

东北及邻区过去两万年来有机碳同位素记录特征

末次冰盛期(LGM)距今大约21ka,两万年来气候演化是过去气候变化研究的重要内容,也是预测未来气候变化的关键。基于湖泊、泥炭长链正构烷烃单体碳同位素(δ^(13)C)和土壤有机质碳同位素(δ^(13)CSOM)记录,重建了LGM以来东北及邻区区碳同位素时间演化序列。结果表明,从LGM至早全新世δ^(13)C值增加至最大值(-23‰),中全新世下降后趋于稳定。对比古气候记录,揭示LGM以来有效湿度可能是东北及邻区δ^(13)C值变化的主导因素。

西南喀斯特地区生物防火阻隔带建设初探——以贵州省毕节市为例

在现有森林防火建设基础上,毕节市紧紧结合国家政策导向、支持方向、资金投向,实施生物防火阻隔带建设,进一步提升和完善林火阻隔系统,补齐当前森林草原防火重要基础设施存在的突出短板,有效制止林火蔓延,减少森林火灾所造成的影响和损失,对西南喀斯特地区生物阻隔带建设,推进森林防火治理建设和发展具有重要作用。

西南地区水平向地震动设计谱参数特征分析

设计反应谱是抗震设计的重要依据,控制设计谱取值的特征参数受到统计的地震动数据的影响,而地震动具有区域性差异,因此设计谱特征参数确定时应考虑区域地震动的特征。基于我国西南地区276次地震的3084条地震动记录,应用高稳定性的GLDE算法和设计谱四阶段模型,对西南地区的设计谱参数进行标定,并对结果进行了比较和验证。将标定结果与我国规范谱的特征参数进行对比,分析了基于地震分组的西南地区设计谱特征参数:放大系数最大值(β_(max))、第一拐点(T_(0))、特征周期(T_(g))、第三拐点(T_(d))和下降段衰减指数(γ)的计算结果。结果表明:对于西南地区,第一拐点略大于现行规范谱的值,特征周期与现行值均有不同,第三拐点、放大系数的最大值和长周期段衰减指数均大于现行值。研究结果可为区域性设计谱的建立提供参考。

Tectonic implications of Late Paleozoic stratigraphic distribution in Northeast China and adjacent region

An analysis of the distribution of the Late Paleozoic strata on Northeast China and adjacent region reveals a zonal pattern of the distribution around the core of the Jiamusi-Mongolia Block. The main part of Late Paleozoic marine strata in this area is co

代际责任视角下农村早婚形成机制及脆弱性研究——基于黔东农村的田野调查

我国主流婚姻模式虽然已转型为晚婚,但是在部分农村地区仍然持续存在早婚现象。基于黔东农村的实证研究发现,父代的低度代际责任是当地农村青年早婚不断涌现的主要原因,它在婚恋方式、生育观念和婚姻决策等方面都影响着早婚的产生。养育责任中的底线逻辑导致家庭规训的缺位,从而助长了青年自由恋爱的过早发生。教育责任中顺其自然的观念延缓了生育观念的现代转型,早孕倒逼结婚成为地方性知识。婚姻责任中的有限资源支持削弱了父代对子代婚姻的经济宰制,进一步强化婚姻决策的自主性。值得警惕的是,由于缺乏联结家庭生活的强整合与牢固的家庭情感,大部分早婚家庭难以长久维持下去,最后往往以成婚不成家而宣告结束。

华北板块南缘及邻区地震活动性与构造模式演化的关系

在进行区域地震活动性分析时,空间范围选取不同,研究结果也将存在差异。在我国省级地震会商中,目标空间范围多由人工划分,若该研究区间包含多个构造背景不同的区域,地震危险性参数扫描结果的准确性将有待验证。采用机器学习方法,按照地震空间分布密度区进行空间聚类,将华北板块南缘及邻区划分为3个区域,结合研究区域地质构造的作用特征,分析3个区域内b值、响应比及频度在不同构造模式作用下的物理意义。结果表明:①在做小区域范围地震活动性分析时,按照与同一构造模式的空间分布选取研究范围和地震震级更为合适;②研究区域地震学指标频繁的同步变化与其复杂的断裂系较为吻合;③地处区域3的南襄盆地和区域2的江汉盆地为同一时期的2个大的断陷盆地,由于盆地处于整体坳陷阶段,因此断裂在地震活动性和对盆地沉积的控制方面均明显较弱,但2个区域近年来地震活动呈增强趋势。因此,按照构造演化模式划分空间研究范围,地震活动性的物理意义更明确,且在同一区域内,地震活动性对同一断裂系上远大震应力传递作用的影响反映比较明显。