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1.
Wang Xiangdong Hu Keyi Qie Wenkun Sheng Qingyi Chen Bo Lin Wei Yao Le Wang Qiulai Qi Yuping Chen Jitao Liao Zhuoting Song Junjun 《中国科学:地球科学(英文版)》2019,62(1):135-153
The Carboniferous period lasted about 60 Myr, from ~358.9 Ma to ~298.9 Ma. According to the International Commission on Stratigraphy, the Carboniferous System is subdivided into two subsystems, i.e., Mississippian and Pennsylvanian, including 6 series and 7 stages. The Global Stratotype Sections and Points(GSSPs) of three stages have been ratified, the Tournaisian, Visean, and Bashkirian stages. The GSSPs of the remaining four stages(i.e., the Serpukhovian, Moscovian,Kasimovian, and Gzhelian) have not been ratified so far. This paper outlines Carboniferous stratigraphic subdivision and correlation on the basis of detailed biostratigraphy mainly from South China, and summarizes the Carboniferous chronostratigraphic framework of China. High-resolution biostratigraphic study reveals 37 conodont zones, 24 foraminiferal(including fusulinid) zones, 13 ammonoid zones, 10 brachiopod zones, and 10 rugose coral zones in the Carboniferous of China. The biostratigraphic framework based on these biozones warrants the precise correlation of regional stratigraphy of China(including2 subsystems, 4 series, and 8 stages) to that of the other regions globally. Meanwhile, the Carboniferous chemo-, sequence-,cyclo-, and event-stratigraphy of China have been intensively studied and can also be correlated worldwide. Future studies on the Carboniferous in China should focus on(1) the correlation between shallow-and deep-water facies and between marine and continental facies,(2) high-resolution astronomical cyclostratigraphy, and(3) paleoenvironment and paleoclimate analysis based on geochemical proxies such as strontium and oxygen isotopes, as well as stomatal indices of fossil plants. 相似文献
2.
代表性人口空间分布数据集的精度评价——以2010年广东省为例 总被引:1,自引:0,他引:1
以人口密度差异显著的广东省为研究区,比较Worldpop、GPW v4和2种中国公里网格人口分布数据集的空间分布一致性,并以第六次全国人口普查数据为真值,按人口密度分为高、中、低3组,从误差的数值分布和空间分布两方面定量评价4种数据集的精度,最后讨论估算误差的可能来源及数据适用性。结果表明,4种网格人口数据集中Worldpop整体精度最高,且在人口密集区的精度也是最高;GPW v4在低人口密度和中人口密度区域精度略高于Worldpop,但对镇街内人口分布细节刻画不够详细;2种中国公里网格人口分布数据集精度较前两者低,主要受空间化方法和模型变量的选择所限制。Worldpop适合用于人口密度中等及人口密度高区域的精细化研究,GPW v4适合用于长时序、最小研究单元大于镇街的研究,第一种中国公里网格人口分布数据集适合用于需要考虑镇街内人口分布和空间异质性的研究,第二种中国公里网格人口分布数据集适用于需要考虑人口分布细节和空间格局变化的长时序研究。 相似文献
3.
Journal of Geographical Sciences - In recent years, flows of many rivers and lakes have become reduced in arid and semi-arid regions around the world. The most typical examples of this phenomenon... 相似文献
4.
Li Nan Li Baolin Chen Dong Wang Enyuan Tan Yuyang Qian Jiawei Jia Haishan 《Natural Resources Research》2020,29(6):3653-3674
Natural Resources Research - Some industrial activities, such as underground mining, hydraulic fracturing (HF), can cause microearthquakes and even damaging earthquakes. In recent years, with the... 相似文献
5.
Deepwater sediments are prone to loss circulation in drilling due to a low overburden gradient. How to predict the magnitude of leak-off pressure more accurately is an important issue in the protection of drilling safety and the reduction of drilling cost in deep water. Starting from the mechanical properties of a shallow formation and based on the basic theory of rock-soil mechanics, the stress distribution around a borehole was analyzed. It was found that the rock or soil on a borehole is in the plastic yield state before the effective tensile stress is generated, and the effective tangential and vertical stresses increase as the drilling fluid density increases; thus, tensile failure will not occur on the borehole wall. Based on the results of stress calculation, two mechanisms and leak-off pressure prediction models for shallow sediments in deepwater drilling were put forward, and the calculated values of these models were compared with the measured value of shallow leak-off pressure in actual drilling. The results show that the MHPS (minimum horizontal principle stress) model and the FIF (fracturing in formation) model can predict the lower and upper limits of leak-off pressure. The PLC (permeable lost circulation) model can comprehensively analyze the factors influencing permeable leakage and provide a theoretical basis for leak-off prevention and plugging in deepwater drilling. 相似文献
6.
7.
Full moment tensor inversion constrained by double-couple focal mechanism for induced seismicity* 下载免费PDF全文
In this study, we propose a new method to determine full moment tensor solution for induced seismicity. This method generalizes the full waveform matching algorithm we have developed to determine the double-couple (DC) focal mechanism based on the neighbourhood algorithm. One major difference between the new method and the former one is that we adopt a new misfit function to constrain the candidate moment tensor solutions with respect to a reference DC solution in addition to other misfit terms characterizing the waveform matching. Through synthetic tests using a real passive seismic survey geometry, the results show the new constraint can help better recover the DC components of inverted moment tensors. We further investigate how errors in the velocity model and source location affect the moment tensor solution. The synthetic test results indicate that the constrained inversion is robust in recovering both the DC and non-DC components. We also test the proposed method on several real induced events in an oil/gas field in Oman using the same observation system as synthetic tests. While it is found that the full moment tensor solutions without using the DC constraints have much larger non-DC components than solutions with the DC constraints, both solutions are able to fit the observed waveforms at similar levels. The synthetic and real test results suggest the proposed DC constrained inversion method can reliably retrieve full moment tensor solutions for the induced seismicity. 相似文献
8.
Natural Hazards - Using the observed daily precipitation data across East China, this paper analyzes spatiotemporal changes of annual and seasonal extreme precipitation indices during... 相似文献
9.
卡里马塔海峡水体交换的季节变化 总被引:2,自引:0,他引:2
Four trawl-resistant bottom mounts, with acoustic Doppler current profilers(ADCPs) embedded, were deployed in the Karimata Strait from November 2008 to June 2015 as part of the South China Sea-Indonesian Seas Transport/Exchange and Impact on Seasonal Fish Migration(SITE) Program, to estimate the volume and property transport between the South China Sea and Indonesian seas via the strait. The observed current data reveal that the volume transport through the Karimata Strait exhibits significant seasonal variation. The winteraveraged(from December to February) transport is –1.99 Sv(1 Sv=1×10~6 m~3/s), while in the boreal summer(from June to August), the average transport is 0.69 Sv. Moreover, the average transport from January 2009 to December2014 is –0.74 Sv(the positive/negative value indicates northward/southward transport). May and September are the transition period. In May, the currents in the Karimata Strait turn northward, consistent with the local monsoon. In September, the southeasterly trade wind is still present over the strait, driving surface water northward, whereas the bottom flow reverses direction, possibly because of the pressure gradient across the strait from north to south. 相似文献
10.
Modelling the transverse behaviour of circular tunnels in structured clayey soils during earthquakes
Acta Geotechnica - The paper presents novel results from advanced numerical simulations of the transverse behaviour of shallow circular tunnels in natural clays accounting for soil structure... 相似文献