Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen-tral-western China

采用中国中西部地区(2l°～36°N，98°～112°E)193个地震台在1992～1999年间记录到的9988次地震的Pg和Sg震相走时的读数资料，用Roecker的SPHYPIT90程序，反演了该地区三维地壳P波速度结构，并用SPHREL3D90程序进行了地震的重新定位．反演结果揭示了中国中西部地区地震P波速度结构明显的横向不均匀性，这些不同深度上波速的横向变化多以该地区的活动断裂为分界线．可以看出活动断裂两侧存在明显的速度反差．通过重新定位，得到了6459次地震的震源参数，这些精确定位的地震震中明显沿该区活动断裂呈现条带状分布，其范围和尺度清晰地表示了这一地区地震活动与活动断裂的紧密关系．其中，82％重新精确定位的事件的震源深度在20km以内．这一结果与笔者用双差地震定位法得到的重新定位的震源深度分布相一致．

The Crustal Structure and Assembly of Terranes in the Qaidam-Qilian-Beishan Area, Western China

Abstract: Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect constitutes a long geotransect which runs across the western Chinese continent.

The winter western boundary current of the South China Sea:physical structure and volume transport in December 1998

The unique survey in December 1998 mapped the entire western boundary area of the South China Sea（SCS）,which reveals the three-dimensional structure and huge volume transport of the swift and narrow winter western boundary current of the SCS（SCSwwbc） in full scale. The current is found to flow all the way from the shelf edge off Hong Kong to the Sunda Shelf with a width around 100 km and a vertical scale of about 400 m. It appears to be the strongest off the Indo-China Peninsula, where its volume transport reached over 20×10~6 m^3/s. The current is weaker upstream in the northern SCS to the west of Hong Kong. A Kuroshio loop or detached eddy intruded through the Luzon Strait is observed farther east where the SCSwwbc no more exists. The results suggest that during the survey the SCSwwbc was fed primarily by the interior recirculation of the SCS rather than by the＂branching＂ of the Kuroshio from the Luzon Strait as indicated by surface drifters, which is likely a near-surface phenomenon and only contributes a minor part to the total transport of the SCSwwbc. Several topics related to the SCSwwbc are also discussed.

Crustal density structures and isostasy beneath the Western North China craton,Trans-North China Orogen,and surrounding regions

To determine the lateral and vertical variations in crustal structure and their influence on the seismicity of the Western North China Craton,the Trans-North China Orogen,and the surrounding regions,the wavelet multi-scale structures,Moho depth,crustal density structures,and isostatic state are modelled using Bouguer gravity anomaly data,topography,and earthquake focal mechanisms.We obtained homogeneous crustal densities and deviations of<1 km between the crustal thicknesses estimated from the isostatic model and those inverted from the Bouguer gravity anomalies in the Ordos Block,the Inner Mongolia Suture Zone,the Sichuan Basin,and the Jizhong Depression.These results provide new evidence for relatively simple and stable continental crustal structures,and indicate that these regions will remain stable in both the vertical and lateral directions.The Hetao Graben,Yinchuan Graben,Weihe Basin,and Shanxi graben system have heterogeneous crustal densities and are isostatically over-compensated.In contrast,the crust beneath the Yinshan Uplift,Lvliang Uplift,and northern and central Taihang Uplift is thin and under-compensated.The heterogeneous crustal densities and non-isostatic state beneath the Tibetan Plateau and Qinling Central China Orogen indicate that these two blocks are unstable in the vertical and lateral directions.Although Cenozoic deformation of the North China Craton is thought to be driven by lithospheric stresses related to the India-Eurasia collision and Pacific slab retreat in South East Asia,we suggest that gravitational potential energy created by the heterogeneous crustal structure modulates these first-order forces.The results of this study could constrain the causes of seismicity in systems surrounding the Ordos Block.

Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in central-western China

A simultaneous inversion of earthquake relocation and three-dimensional crustal structure of P-wave velocity in central-western China (21癗~36癗, 98癊~112癊) were performed in this paper. The crustal P-wave velocity model and earthquake relocation for this region are obtained using Pg and Sg phase readings of 9 988 earthquakes from 1992 to 1999 recorded at 193 seismic stations within central-western China by SPHYPIT90 and SPHREL3D90 programs. A lateral inhomogeneous structure of P-wave velocity in this region was obtained. Ob-vious contrast of P-wave velocities was revealed on both sides of active fault zones. Relocated epicenters of 6 459 events show clear lineation along active faults, which indicated a close correlation between seismicity and the active faults in this region. Focal depths of 82% relocated events ranged from 0 to 20 km, which is in good agreement with that from double-difference earthquake location algorithm.

Agricultural Structure in Western China by Comparing with before and after CFFG Based on Shift-share Method

Based on shift-share method,this article employs regional share,structural shift and competitive shift to analyze the structural benefit and competitive position of agricultural structure in western China by comparing with agriculture,foresting,stockbreeding and fishing before and after Conversion of Farmland to Forest and Grassland(CFFG) .Then authors draw following conclusion:while CFFG program has been put in practice,the agricultural structure in western China has some typical characteristics,such as growth faster,structural predominance obvious and more competitive.But the contributiveness from the competition is not too much yet,and the structural benefit of forest estate and stockbreeding are restrained.

The Key Influence of Fluid in the Preserves, Mineral Assemblages, Compositionsand Structures: Study from High-Pressure Eclogite and Its Amphibolization in the Western Dabie Mountains,Central China

Pseudosection modeling for the garnet amphibolite samples from the Western Dabie Mountains show they have experienced similar HP metamorphic evolution with that of the adjected eclogites.The common assemblage of

The Key Influence of Fluid in Metamorphic Rock Preserves, Mineral Assemblages, Compositions and Structures: Study from High-Pressure Eclogite and Its Amphibolization in the Western Dabie Mountains,Central China

The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should

Thermal Structure and Rheology of the Upper Mantle Derived from Mantle Xenoliths from Gansu Province, Western China

Mantle xenoliths brought up by Cenozoic volcanic rocks onto the earth’s surface may provide direct information about the upper mantle beneath the volcanic region. This paper presents the study on mantle xenoliths collected from Haoti village, Dangchang County, Gansu Province, western China. The main purpose of the study is to gain an insight into the thermal structure and rheology of the upper mantle beneath the region. The results show that the upper mantle of the region is composed mainly of spinel lherzolite at shallower depth (52～75km), and garnet lherzolite at greater depth (greater than 75km), instead of harzburgite and dunite as proposed by some previous studies. The upper mantle geotherm derived from the equilibrium temperatures and pressures of xenoliths from the region is lower than that of North China, and is somewhat closer to the Oceanic geotherm. The crust-mantle boundary is determined from the geotherm to be at about 52km, and the Moho seems to be the transition zone of lower crust material with spinel lherzolite. If we take 1280℃ as the temperature of the top of asthenosphere, then the lithosphere-asthenosphere boundary should be at about 120km depth. The differential stress of the upper mantle is determined by using recrystallized grain size piezometry, while the strain rate and equivalent viscosity are determined by using the high temperature flow law of peridotite. The differential stress, strain rate and viscosity profiles constructed on the basis of the obtained values indicate that asthenospheric diapir occurred in this region during the Cenozoic time, resulting in the corresponding thinning of the lithosphere. However, the scale and intensity of the diapir was significantly less than that occurring in the North China region. Moreover, numerous small-scale shear zones with localized deformation might occur in the lithospheric mantle, as evidenced by the extensive occurrence of xenoliths with tabular equigranular texture.

Response of Phytoplankton Community Structure and Size- Fractionated Chlorophyll a in an Upwelling Simulation Experiment in the Western South China Sea

The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a(Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.

Pygostyle-like Structure from Beipiaosaurus(Theropoda,Therizinosauroidea)from the Lower Cretaceous Yixian Formation of Liaoning,China

Pygostyle was previously considered as a unique structure of ornithothoracine birds, used to maneuver tail feathers. A similar structure from an oviraptorosaurian dinosaur was considered functionally associated with the rectrices as in birds. We report a pygostyle-like structure from a therizinosauroid dinosaur. The presence of filamentous integuments, but absence of rectrices, on the tail of this therizinosauroid, combined with other lines of evidence, suggests that the initial function of the pygostyle was not related to the rectrices.

Structural Styles of Fronts of Thrust-Detachment Faults in Petroleum-bearing Areas of Western China

The front of a thrust-detachment fault may have various styles such as decoupling, fold, forethrust and backthrust ones because of differences in magnitude, direction and time of the forces exerted on the fault and the inhomogeneity of rock mechanical properties. They have different characteristics and are usually associated with gravity structure, inverse structure and diapir structure. These structures exist together in the same thrust-detachment fault and can influence, compensate for and convert into each other. They provide important grounds not only for the study of the dynamic state, propagation mode, evolutionary process and formation mechanism but also for the analysis of the petroleum generation, migration, accumulation and preservation and arrangement of drill holes in foreland basins.

Large-scale gas accumulation mechanisms and reservoir-forming geological effects in sandstones of Central and Western China

Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects.Based on the geological theory and method of natural gas reservoir formation,this study examined the regional geological and structural background,formation burial evolution,basic characteristics of gas reservoirs,and fluid geology and geochemistry of typical petroliferous basins.The results show that the geological processes such as structural pumping,mudstone water absorption,water-soluble gas degasification and fluid sequestration caused by uplift and denudation since Himalayan stage all can form large-scale gas accumulation and different geological effects of gas accumulation.For example,the large-scale structural pumping effect and fluid sequestration effect are conducive to the occurrence of regional ultra-high pressure fluid and the formation of large-scale ultra-high pressure gas field;mudstone water absorption effect in the formation with low thickness ratio of sandstone to formation is conducive to the development of regional low-pressure and water free gas reservoir;the water-soluble gas degasification effect in large-scale thick sandstone can not only form large-scale natural gas accumulation;moreover,the degasification of water-soluble gas produced by the lateral migration of formation water will produce regional and regular isotopic fractionation effect of natural gas,that is,the farther the migration distance of water-soluble gas is,the heavier the carbon isotopic composition of methane formed by the accumulation.

Urbanization in Western China

China has experienced considerable urbanization in the past 60 years,especially since the implementation of the Economic Reform and Opening-up Policy in 1978.In 1949,there were only 132 cities with an urban population of 27.4 million,while in 2008 China had 652 cities with a total urban population of 606 million.Such urbanization is attributed to the boost in the number of cities and the urban population.Urban expansion enhanced geographic inequality between the three major regions in China.Compared with the eastern and central regions,western China only has 19%of the total cities and 18%of the urban population.The urbanization rate was 37.2%for the western region in 2008,while it reached 53.3%for the eastern regions and 45.3%for central China.Using a geographic information system(GIS)and statistical analyses,this study aims at explaining the structure and spatial development of urbanization,and highlighting the current issues of urban inequality in western China during the past two decades.The paper drew following conclusions:(1)Urbanization disparities between eastern and western China have become increasingly obvious,but seem to be evolving slowly since the establishment of the government's Western Development Priority Policy in 2000.(2)Cities of various sizes were expanded in western China,and the main factors affecting the urbanization are population numbers and density,government investment and geographic conditions.(3)Current patterns of urbanization in the western region are distributed unevenly between provinces.

绿色物流与低碳经济系统协调度评价及其影响因素研究——基于西部地区面板数据的实证分析

通过构建绿色物流与低碳经济耦合协调度模型,对西部地区11个省(市、区)2011-2021年绿系统耦合协调水平进行测算,并利用Stata18软件对其影响因素进行定量分析。结果表明:(1)西部地区各省份两个系统之间的耦合关系基本呈现稳中上升的态势,整体耦合协调度稳定在0.5-0.6附近,趋于初级协调阶段。(2)经济发展水平、产业结构、技术创新水平、政府支持程度、能源结构对西部地区绿色物流与低碳经济耦合协调水平均具有显著性影响。其中,能源结构呈现显著性负向影响。依据研究结果,提出建议:加强绿色物流和低碳技术研发、加大绿色物流投入、加快实现能源资源高效转化等措施,推进西部地区绿色物流与低碳经济协同发展。

科教融汇视域下西部高等教育结构的困境检视与功能重塑

在教育强国建设进程中,优化区域高等教育结构布局,是我国西部高等教育实现高质量发展的重要举措。科教融汇新理念的提出,为新时代西部高等教育结构优化与布局调整提供了方向指引。全面振兴西部高等教育,需坚持以科教融汇为新方向,在层次结构上凸显人才梯队培养,在科类结构上服务科技产业升级,在形式结构上形塑科研生态系统,在布局结构上优化科研资源配置。然而,在实践层面,西部高等教育当前仍面临较为突出的结构性问题,在支撑引领区域科技创新、产业升级等方面的功能尚未得到充分发挥,包括人才培养层次结构重心偏低,高科技人才缺口大;高校学科专业结构适应性差,科技驱动能力不足;形式结构内部要素协同性弱,科研合作机制不畅;优质教育资源布局结构失衡,科技创新活力不足。站在新的历史起点,在普及化初级阶段,西部高等教育应在科教融汇理念指导下,遵循整体性、协调性、适应性和开放性原则,深化科教融汇育人理念,逐步上移层次结构重心;立足科技产业发展需要,动态调整学科专业结构;推动西部高校集群发展,促进形式结构协同联动;加强科技创新开放合作,完善科研设施布局结构。

西部地区城市群空间结构调整的经济增长效应:基于动态空间计量模型的检验

城市群已成为中国西部地区经济发展的重要增长极与核心区,其合理有序的空间结构是经济增长的重要源泉。文章基于西部地区八大城市群2004—2020年面板数据,利用动态空间杜宾模型检验西部地区城市群空间结构调整对经济增长的作用效果与作用机制。研究发现:西部地区城市群的人口、产业和土地利用空间结构调整主要表现为空间集聚并显著促进了城市群经济增长;进一步的检验发现,这三类空间结构集聚对经济增长的促进作用在不断增强,且由短期促进演变为短期促进与长期促进并存。在影响机制方面,西部地区城市群人口空间集聚因加重环境污染而抑制了经济增长,但抑制作用明显弱于正向促进作用;产业空间集聚通过促进技术进步推动了经济增长;土地利用空间集聚通过加快产业结构升级促进了经济增长。最后,文章提出了提升城市群中心城市人口承载能力、提高城市群第二产业和第三产业空间集聚度、提高建设用地空间集聚度等政策建议。

亚洲传播学研究的现状与未来

本文探讨了促进亚洲传播研究发展的机遇与挑战。作者认为,亚洲传播研究需要超越传统的西方理论框架,关注本土文化和语境,探索以亚洲为中心的理论或范式。亚洲传播的实践也面临着来自不同层级的结构性因素的挑战。作者指出,中国在亚洲传播研究崛起中扮演着重要角色,亚洲学者应积极参与全球话语模型中的话语范式构建,与全球传播研究进行对话。

Multi-oriented and layered structures of lithosphere in erogenic belt and their effects on Cenozoic magmatism——A case study of western Yunnan and Sichuan, China

Integrating the surface structures with the reinterpretations of 3-D velocity images, this paper puts forward a kind of multi-oriented and layered structure for those of the upper and mid-lower crust, lithospheric and asthenospheric mantle in Tethyan erogenic belt of western Yunnan and Sichuan, China (Sanjiang belt). There exists a detachment between upper and mid-lower crust. The lithospheric mantle is a rigid and competent body unable to be deformed which preserved the older tectonic framework. The asthenosphere is an imcompetent layer that is easy to be deformed, and behaves as an initiation region of deformation, and its structural patterns reflect younger tectonics. The Cenozoic intracontinental magmatism of this region is controlled by: (i) sub-meridional and NNE trending asthenospheric upwelling around the western margin of Yangtze block; (ii) crust-mantle transitional layer formed by underplating of ascending melts; and (iii) intersection or transformation of regional structures such as major faults.

密度成像技术在南海西部油田地质导向中的应用

水平井施工过程中已广泛应用随钻地质导向技术,在持续发展储层随钻测绘等新技术过程中,密度成像技术在随钻地质导向技术中的应用仍然较为普遍。针对南海西部Z油田井控程度低、构造变化大、储层横向变化快等问题,引入了密度成像工具和相应的地质导向技术。借助高分辨率密度成像成果拾取精确的地层倾角,在此基础上分析落实构造形态,判断轨迹所处的相对位置;配合地质录井确定的岩性情况,避免局部相变造成的出层;从而为实时决策提供判断依据并指导地质导向。实施过程中首次提出并使用了过井轴视倾角的概念,改进了常规利用成像数据计算地层倾角的方法并通过实际对比验证;该区块目前已完钻4口水平井,平均长度580 m,优质储层钻遇率80%。结论认为:在密度变化明显的构造+岩性油藏中使用该技术,能有效降低构造不确定性等地质风险,提高优质储层钻遇率。