2017 Vol. 23, No. 1

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REVIEWS ON THE RESSEARCH OF LATE CENOZOIC GEOLOGY AND ENVIRONMENT OF THE YANGTZE RIVER DELTA AREA
ZHAO Xi-tao, HU Dao-gong, WU Zhong-hai, YANG Xiao-dong
2017, 23(1): 1-64.
Abstract (180) HTML (56) PDF (39021KB)(71)
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The Yangtze River is the longest river in China and one of the most main rivers in the world. The Yangtze River delta area is one of the most densely populated and economically developed areas in China. Therefore, studying characteristics and changes of Late Cenozoic geology and environment of the area is of very important significance for national welfare and the people's livelihood there. This kind of studies has had a whole century of history. With the development of economy and the progress of science and technology, some major progress has been made in this studies. In this paper we reviewed progress made on basis of data of such aspects as the modern development of the Yangtze River delta, incision and filling of the Yangtze River valleys during the latest pleniglacial age, changes of sedimentary facies during the post-glacial period, the distribution, characteristics and origin of buried hard earth layers, Late Quaternary transgressive sequences and Neogene and Early-Middle Quaternary stratigraphic units and sedimentary environments in the Yangtze River delta area, sedimentary compositions and geochemical analyses of delta sediments, and age spectrums of detrital zircon and monazite from borehole samples. Among the progress is the time of the Yangtze River breaking through the Three Gorges as an obstacle. At the same time some open questions were also pointed out in this paper. Then according to the reviews, we put forward several suggestions for the coming research to call researchers' attention to produce the effect of throwing away a brick in order to get a gem.
GLOBAL CLIMATE CHANGE AND GEOLOGICAL DISASTER RESPONSE ANALYSIS
GAO Yang, LI Bin, FENG Zhen, ZUO Xiao
2017, 23(1): 65-77.
Abstract (371) HTML (123) PDF (1898KB)(33)
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Since the industrial revolution, due to the global climate change, the world is experiencing global warming in recent decades. The impact of global climate change on extreme weather events (extreme rainfall, high temperatures, strong winds and floods) is particularly strong, and increases the risk of geological disasters. Water cycle and temperature change are the direct factors incuring geological disasters. The rise of temperature leads to the increase of water content in the atmosphere, the glacier permafrost degradation, sea-level rise, and evaporation enhancement. The change of water cycle will lead to changes in the frequency of rainfall, the cycle of precipitation, and the intensity of precipitation. Increasing extreme weather and soil interact lead to the occurrence of different types of geological disasters, which are serious threats to human life. In this paper, the response to geological disasters under global climate change, especially landslide and debris flow disasters, and the mutual relations are reviewed.
STUDY ON CONTROL MEASURES OF COUNTER-TILT ROCK LANDSLIDE IN THREE GORGES RESERVOIR REGION
TAN Weijia, DAI Zhenwei, CHEN Yunxia,
2017, 23(1): 78-87.
Abstract (192) HTML (106) PDF (4114KB)(17)
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In this paper, Maocaopo in the Wu Gorge section, a typical anti-dip rock landslide, was taken as the research object to describe the phased design process of prevention and control measures for this type of landslide (principle, idea and method):First, the deformation failure process and the current deformation stage of the bank slope were analyzed on the basis of existing geological survey data and the characteristics of bank slope deformation failure at the current stage, so as to determine the corresponding instability mode and main control factors, then propose alternative schemes for landslide prevention and control. Second, different deformation failure stages of the landslide were reasonably divided. Numerical simulation was applied to carry out whole-process evaluation of the outcome of each alternative scheme for landslide prevention and control at different deformation failure stages of the bank slope. Reasonable prevention and control measures were established through comparative analysis. Main conclusions of the research include the followings:(1) For the same bank slopes, their deformation failure mode and main control factors are not exactly the same at different deformation stages, and the same prevention and control scheme renders significantly different outcomes. (2) For the current stage of Maocaopo, the landslide is at the slope toe weakening and slipping stage of the deformation failure process. The main control factor of deformation failure at this stage is the weakening and slipping of rock mass in the hydro-fluctuation belt. The scheme of slope protection with lattice needs a lower construction cost and produces a better prevention and control effect, while the scheme of bolt anchoring needs a higher construction cost but has a poorer effect.
DISCUSSION ON THE SCALE PROBLEM IN REMOTE SENSING DATA FOR LOESS LANDSLIDE SURVEY IN BAOJI, SHAANXI PROVINCE, CHIAN
XU Gang
2017, 23(1): 88-96.
Abstract (165) HTML (55) PDF (2512KB)(9)
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The content and accuracy are determined by the scale of remote sensing(RS) data, the RS Processing molds or methods vary with Remote sensing data scale in the same region. Based on the landslide RS survey in Baoji loess area, we discuss the problems that have great relationship with RS scale, such as Mininum regional area of landslide mass in different RS data source, precision measurement of spot area, the best and maxinum mapping scale, comparative analysis of interpretation of RS geological hazards, accuracy evaluation of landslide RS interpretation and so on. The result reveals that when investgating large and medium-sized landslide in Baoji loess area, SPOT-5(2.5 m)Fused image data can be used, and the scale is 1:25000 or 1:50000. Meanwhile, QuickBird(0.61m)Fused image data is used for medium-small landslide and quantitative information calculation on the internal structure of larger landslide, and the scale is 1:5000.
LANDSLIDE SUSCEPTIBILITY ASSESSMENT IN THE THREE GORGES AREA, CHINA, ZIGUI SYNCLINAL BASIN, USING GIS TECHNOLOGY AND FREQUENCY RATIO MODEL
QI Xin, HUANG Bo-lin, LIU Guang-ning, WANG Shi-chang
2017, 23(1): 97-104.
Abstract (127) HTML (82) PDF (3496KB)(12)
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The Three Gorgesarea, China, Zigui synclinal basin is selected as a case study in this paper. Based on the field of landslide mapping, in the frequency ratio model, slope angle, lithology, rivers, roads, aspect and beeding-aspect this six assessment factors are considered to assess landslide susceptibility by overlaying analysis using GIS technology to calculate the contribution rate separately, Ultimately, landslide susceptibility area is divided into four partitions. The results shows that the vey high susceptibility area accounts for 21.39 percent and landslide area accounts for 61.44 percent. high susceptibility area accounts for 24.99 percent and landslide area accounts for 21.67 percent. Moderate susceptibility area accounts for 30.66 percent and landslide area accounts for13.19 percent. Low susceptibility area accounts for 22.93 percent and landslide area accounts for 3.69 percent. The cumulative percentage curve of landslide susceptibility area shows that the results are highly accurant and reliable, what to provide scientific support for the government about disaster prevention and reducing engineering, and provide scientific basis to landslide forecast and management.
IN-SITU DIRECT SHEARING TEST ON LANDSLIDE ACCUMULATION BODY INTENSITY OF WENCHUAN EARTHQUAKE REGION
WU Rui-an, ZHANG Yong-shuang, WANG Xian-li, YAO Xin, YANG Zhi-hua, DU Guo-liang
2017, 23(1): 105-114.
Abstract (136) HTML (47) PDF (3510KB)(8)
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In this paper, the earthquake-induced loose sediments near Xuankou, Wenchuan County, Sichuan province are selected to conduct the in-situ direct shear tests of undisturbed gravel soil and remolded soil sample direct shear tests with different situations to explore the shear properties of gravel soils under different vertical pressure, particle size composition and moisture. The study results show that (1) Gravel soils which have similar geological genesis, similar rock mass structure, different size composition and poor gradation have similar shear properties and shear strength. (2) The shear strength of undisturbed gravel soil samples is significantly higher than remolded samples with the same dry density and moisture. (3) Strain hardening strength of well-graded gravel soils is slightly higher than bad-graded gravel soil, when the content of coarse particle whose size is greater than 5 mm is more than 42.9%, friction angle increases with increment of coarse-grained contents, while cohesion decreases firstly and then increases. (4) When moisture content is more than 15.8%, there is a negative correlation between shear strength indexes and moisture content, with gradual increase of moisture, the shear strength of gravel soil will gradually reduce, among which the decrease of cohesion is more remarkable than internal friction angle. Considering others' research and experimental results, we suggest that the gravel soils having similar structure components in Wenchuan earthquake area can select the shear strength indexes c of 15±3kPa and Phi of 30°±2°.
LANDSLIDE HAZARD RAPID ASSESSMENT IN THE Ms 8.1 NEPAL EARTHQUAKE-IMPACTED AREA, BASED ON NEWMARK MODEL
YANG Zhi-hua, ZHANG Yong-shuang, GUO Chang-bao, DU Guo-liang
2017, 23(1): 115-124.
Abstract (220) HTML (101) PDF (4834KB)(27)
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April 25, 2015, an Ms8.1 earthquake occurred in Nepal with epicenter of 28.2°N, 84.7° E and focal depth of 20 km. The earthquake and induced landslides caused serious casualties and economic losses in Nepal and southwest Tibet of China. After the earthquake, the earthquake-induced landslide hazard distribution offered information to timely relief activities. Based on the detailed analysis of geomorphology, lithology, tectonics, hydrology and typical landslides, the sophisticated Newmark model and Geographic Information System were adopted to complete the rapid assessment of landslide hazard distribution in the Nepal earthquake-impacted area. The assessment results had good confidence by the verification in terms of landslide cases coming from remote sensing interpretation in partial regions and initially reflected the basic characteristics of Nepal earthquake-induced landslide hazard distribution. Then, considering the post-earthquake rainfall effect that can significantly initiate landslides, the landslide hazard rapid assessment under the combined effect of seismic motion and heavy rainfall was completed. The landslide hazard rapid assessment results can provide important references to geo-hazard prevention and mitigation during post-earthquake emergent relief activities.
ELECTROMAGNETIC DATA APPLICATION IN CARBONIFEROUS EXPLORATION OF EASTERN QAIDAM BASIN
ZENG Qingmeng, LIU Chenglin, , ZHANG Guibin, MAO Zhihui
2017, 23(1): 125-134.
Abstract (112) HTML (49) PDF (4342KB)(10)
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Carboniferous formation in the eastern Qaidam Basin belongs to a new area and new strata and lack of data on well and seismic, so processing and interpretation of electromagnetic data must be valued. New Electromagnetic data in eastern Qaidam Basin was used as the center, constrained with drilling and seismic data, and combined with other exploration data, gravity data to do comprehensive research and joint interpretation in this area. Firstly the electromagnetic data was pre-processing and inversed, mainly using the one-dimensional Bostick inversion, one-dimensional continuous medium inversion, two-dimensional conjugate gradient inversion, 2D continuous medium inversion and optimization of electric-layered inversion technique. Then the electromagnetic data and other data was comprehensively interpreted and researched, thus get some comprehensive research results such as Carboniferous thickness map, Carboniferous buried-depth map, so as to effectively predict the oil traps in eastern Qaidam Basin. At last, some conclusions and recommendations were advised in the Carboniferous exploration of Eastern Qaidam Basin.
ANISOTROPY OF MAGNETIC SUSCEPTIBILITY:THEORY AND CASE STUDIES
ZHANG Shu-wei, YANG Zhen-yu, WANG Xi-sheng, Maria T Cioppa, QIAO Yan-song, HUO Jun-jie, Edgardo Cañón-Tapia, ZHAO Yue
2017, 23(1): 135-140.
Abstract (565) HTML (351) PDF (2091KB)(87)
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Anisotropy of magnetic susceptibility (AMS) has been widely utilized to study orientation of magnetic minerals due to the paleo-flow, and direction of magnetic minerals or their recrystallization caused by tectonic stress. We presented the AMS principle and parameters, and studied AMS changes in:(1) two basalt samples (unheated and heated) that have experienced tectonic deformation, with multidomain (MD) titanomagnetite as dominant magnetic minerals, and this is from a previous study; (2) lake sediments that are majorly characterized by MD magnetite. The results show that AMS can sensitively investigate orientation of magnetic minerals.
CENOZOIC MARINE SEDIMENTATION PROBLEM OF THE TARIM BASIN
LI Jian-feng, ZHAO Yue, PEI Jun-ling, LIU Feng, ZHOU Zai-zheng, GAO Hai-long, GAO Liang, FU Zi-bo
2017, 23(1): 141-149.
Abstract (195) HTML (66) PDF (2866KB)(16)
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Based on former studies, this paper combines the problems on Cenozoic marine sedimentation of Tarim basin and discusses the times and scope of transgression, and time and cause of the Paratethys regression from Tarim basin in Cenozoic. The results suggest that Tarim basin experienced at least three marine incursions in Cenozoic, they are Late Aertashi-Early Qimugen (the Early Paleocene to Late Paleocene), Kalatar-Wulagen (the Middle Eocene) and Middle Bashibulake (the Late Eocene to Early Oligocene). Further evidence is needed for the recognition of the marine strata that existed in Tarim basin in Miocene. The maximum transgression corresponded to the Kalatar-Wulagen. Further, the seawater reached Mazhatagh, then the east of Kuala and the east of Aqike, which are northern and southern margins of Tarim basin, respectively. On the effect of global eustatic sea level change combined with tectonism in Cenozoic, the top of the Qimugen, the top of the Wulagen and, the fourth and fifth segments of the Bashibulake formed due to the Paratethys Sea regression, corresponding to Late Paleocene, Late Eocene and Early Oligocene, respectively.
LATE PALEOZOIC OCEAN-CONTINENT TRANSITION IN WEST JUNGGAR, CENTRAL ASIAN OROGENIC BELT:EVIDENCE FROM LATE CARBONIFEROUS RHYOLITES
SHI Jian-jie, CHEN Xuan-hua, DING Wei-cui, LI Bing
2017, 23(1): 150-160.
Abstract (200) HTML (123) PDF (4770KB)(14)
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The late carboniferous rhyolites with columnar joints have been found in the West Junggar, then we studyed their tectonic environment through the geochemical characteristics. The rhyolites from the West Junggar have the characteristics of high K, low Na, so they belong to high-k calc-alkaline or cala-alkaline magmatic series. According to the Ⅴ patterns of the REE distribution patterns of the rhyolites, Eu is deficited, testifying the process of the crystallization differentiation of plagioclase. The rhyolites are enrichment of elements Rb、K (LILE), and deficient of Nb、Ta(HFSE), this is same to the characteristic of subduction zone magma. The study shows that the rhyolites which belong to A2 rock type derived from post-orogenic tectonic environment. The rhyolites and granites batholith have the same magmatic source and both belong to rich alkaline magmatism in orogenic environment. Similarly to the environment of the rhyolites in the east China, the study proves the existence of sea-land transition zone during the late Paleozoic, indicating that the Junggar Oceanic Plate subducted under the Kazakhstan Plate. Ocean subduction mainly developed in Karamay-Baogutu area, where the Junggar oceanic plates subducted to the northwest under the Kazakhstan plates. The rich alkaline magmatism in the post-orogenic stretch environment which the late carboniferous rhyolites with columnar joins occured, put an end to the ocean-land transition environment.
THE SEISMOGENIC MECHANISM OF STRONG EARTHQUAKES IN DAYAO-YAOAN AREA:STRUCTURE STRENGTHENING AND ACTIVITY OF THE NW STRIKE FOLD JOINTS
CHANG Zu-feng, ZHANG Yan-feng, LI Jian-lin
2017, 23(1): 161-172.
Abstract (151) HTML (177) PDF (5019KB)(17)
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At the start of this new century, four strong earthquakes of magnitude from 6.0 to 6.5 have successively occurred in Dayao-Yaoan region of central Yunan, we analyzed the structure and its evolution, combined with the modern motion characteristics and tectonic stress field of the Sichuan-Yunnan Block, to confirm the motion model and special seismogenic model of central Yunnan tectonic area and discuss the relationship between joints generated by folds and seismic. The research revealed that all these event sequences arranged in NW direction regularly, with highly consistent mechanical rupture mechanism of dextral strike slip along the NW strike joint plane revealed by focal mechanism solution. This area had no faults, but dominated by many NW strike Mesozoic fold structures. Abundant field investigations attested that plenty of longitudinal joints and transverse joints associated with folds have been developed intensively in this area, the former were more development than the latter. These joints become concentrated belts which array in unequal space, with a width of 30m to 50m and 20m to 30m per miter. On the joint plane, there are calcites and gabbro dykes developed as well as squeezed schistosition belt, fresh striations and soft fault gouge, all these phenomenas suggest that these joints are not only related to deep crust, but also active recently. It is inferred that:under the SSE movement of central Yunan block, these earthquakes produced, with the NW strike longitudinal joints structure strengthening, liking-up and rupturing under the present NNW orientation pressed stress fields. The active joints, just like active faults and active folds, are one of the most widespread active structures on Earth. Joint structures may become structure strengthening or activity belts and then become particular seismogenic structures under particular tectonic circumstance and special tectonic stress field.
THE EVOLUTION OF SEISMIC ACTIVITY IMAGE IN THE HIMALAYA BELT BEFORE AND AFTER 2015 NEPAL M 8.1 GREAT EARTHQUAKE
LIU Jie, ZHAO Gen-mo, WU Zhong-hai
2017, 23(1): 173-181.
Abstract (188) HTML (88) PDF (4163KB)(20)
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Concerning on the future seismic risk brought by Himalaya orogenic belt after the April 25th, 2015 M8.1 Nepal earthquake, we analyze the strain energy release of Himalaya belt historical great earthquakes and study the regional seismicity images of both pre and post Nepal earthquake. The results show that Himalaya belt may has entered a new round of seismic active period. Crustal strain energy in the middle section of Himalaya belt didn't release completely in this earthquake, the earthquake activity is closely associated between the middle section of Himalaya belt and South Tibet Rift zone, there will be great earthquakes occurring in these two places. Assam gap zone and Bhutan gap zone exist on the east segment of Himalaya belt, meanwhile, Gar gap zone exists on the west, the border region of New Delhi and Tibet in western Himalaya belt and the Gar county area on the Karakorum fault have high seismic risk, Assam and Bhutan in southern Nyingchi, Shannan in eastern Himalaya belt also have high seismic risk, so these zones should be paid more attention to.