The Wenchuan Earthquake (May 12, 2008), Sichuan Province,China, and resulting geohazards

On Monday, May 12, 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan Province, China. The focal mechanism of the earthquake was successive massive rock fracturing 15 km in depth at Yingxiu. Seismic analysis confirms that the major shock occurred on the Beichuan–Yingxiu Fault and that aftershocks rapidly extended in a straight northeast–southeast direction along the Longmenshan Fault zone. Fatalities approaching a total of 15,000 occurred, with a significant number resulting from four types of seismically triggered geohazards—rock avalanches and landslides, landslide-dammed lakes (“earthquake lakes”), and debris flows. China Geological Survey has identified 4,970 potentially risky sites, 1,701 landslides, 1,844 rock avalanches, 515 debris flows, and 1,093 unstable slopes. Rock avalanches and landslides caused many fatalities directly and disrupted the transportation system, extensively disrupting rescue efforts and thereby causing additional fatalities. Landslide-dammed lakes not only flooded human habitats in upstream areas but also posed threats to potentially inundated downstream areas with large populations. Debris flows become the most remarkable geohazards featured by increasing number, high frequency, and low triggering rainfall. Earthquake-triggered geohazards sequentially induced and transformed to additional hazards. For example, debris flows occurred on rock avalanches and landslides, followed by landslide-dammed lakes, and then by additional debris flows and breakouts of the landslide-dammed lakes and downstream flooding. Earthquake-induced geohazards occurred mainly along the fault zone and decreased sharply with distance from the fault. It can be anticipated that post-earthquake geohazards, particularly for debris flows, will continue for 5–10 years and even for as long as 20 years. An integrated strategy of continuing emergency response and economic reconstruction is required. The lesson from Wenchuan Earthquake is that the resulted geohazards may appear in large number in active fault regions. A plan for geohazard prevention in the earthquake-active mountainous areas is needed in advance.     

Distribution Characteristics of Gold and Other Trace Elements in the Proterozoic Lengjiaxi Group,Northeastern Hunan Province

Systematic geochemical studies of the Proterozoic Lengjiaxi Group in northeastern Hunan Province suggest that the Lengjiaxi Group is a Au-As-Sb-W association-type Au-bearing turbidite formation.The contents of Au,As,Sb,W,Cr,Mn,Pb and Zn in the turbidite formation are more than two times as high as the average contents of trace elements in the upper continental crust.The low abundance of Ag and the close correlation between Au and As are two important characteristic features.In the Au-bearing turbidite formation the enrichment of gold is due to the extensive occurrence of Au-bearing pyrites.Higher contents of Au,W,Sb and Ag in the greywacke indicate that they also exist in the form of heavy minerals.Au,Ag,As,Sb,W and REE in the Au-bearing turbidite formation have a close genetic relation with the chemistry of the gold deposits.     

A Survey of the Spatio-Temporal Data Model

Traditional GIS(Geographic Information System)mostly can only describe the transient state data and does not have the ability to deal with the temporal dynamic data. When the data changes, new data will take the place of the old data, namely the transient state change into another, and the old data will disappear. Therefore, it is unable to make an analysis of the updating changes of the data and predict the development trend of the future. In this case, TGIS (Temporal Geographic Information System) emerges and expands the time dimension on the basis of traditional GIS. Spatio-temporal data model is the key to TGIS. Spatio-temporal data modeling is not only related to dynamic expression of spatio-temporal objects, but also gives an important support for spatio-temporal analysis and reasoning. This paper summarized the theories and applications status at home and abroad of spatio-temporal data model in detail, illustrated family tree of spatio-temporal data model for the nearly fifty years, discussed improvement and application status of Base State with Amendments Model, Event-based Spatio-temporal Data Model, Object-oriented Data Model and other spatio-temporal data models, and raised the existing problems of spatio-temporal data model. The current existing problems mainly includes: ①There are a lot of spatio-temporal data models put forward, but some of them only focus on semantic design and neglect the verified; ②Most of existing spatio-temporal data model are for vector data, only the Event-based Spatio-temporal Data Model is raster data structure; ③At present, the expression the time-space information of geographic entity is relative separated with spatio-temporal data model; ④Spatio-temporal data model is mainly used in cadastral management, land use and forestry data updating, less application in other fields. In the end, the future development direction was put forward of spatio-temporal data model. In the time of big data and “Internet plus”, it is necessary to explore the big data spatio-temporal data model that supports multiple data formats.     

水力类泥石流冲出规模模拟实验

在物源条件一定的情况下,通过实验模拟,研究水力类泥石流在不同流速、流量和纵比降组合条件下的沟道启动、揭底机理和运动特征。用Herschel-ulkley模型分析泥石流运动时的受力情况,整理实验数据获得侵蚀高度与纵比降的关系和流量与揭底距离的关系。     

Sensitivity assessment of strontium isotope as indicator of polluted groundwater for hydraulic fracturing flowback fluids produced in the Dameigou Shale of Qaidam Basin

Hydrogeochemical processes that would occur in polluted groundwater and aquifer system, may reduce the sensitivity of Sr isotope being the indicator of hydraulic fracturing flowback fluids(HFFF) in groundwater. In this paper, the Dameigou shale gas field in the northern Qaidam Basin was taken as the study area, where the hydrogeochemical processes affecting Sr isotope was analysed. Then, the model for Sr isotope in HFFF-polluted groundwater was constructed to assess the sensitivity of Sr isotope as HFFF indicator. The results show that the dissolution can release little Sr to polluted groundwater and cannot affect the εSr(the deviation of the 87 Sr/86 Sr ratio) of polluted groundwater. In the meantime, cation exchange can considerably affect Sr composition in the polluted groundwater. The Sr with low εSr is constantly released to groundwater from the solid phase of aquifer media by cation exchange with pollution of Quaternary groundwater by the HFFF and it accounts for 4.6% and 11.0% of Sr in polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater, respectively. However, the Sr from cation exchange has limited impact on Sr isotope in polluted groundwater. Addition of Sr from cation exchange would only cause a 0.2% and 1.2% decrease in εSr of the polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater, respectively. These results demonstrate that hydrogeochemical processes have little effect on the sensitivity of Sr isotope being the HFFF indicator in groundwater of the study area. For the scenario of groundwater pollution by HFFF, when the HFFF accounts for 5%(in volume percentage) of the polluted groundwater, the HFFF can result in detectable shifts of εSr(ΔεSr=0.86) in natural groundwater. Therefore, after consideration of hydrogeochemical processes occurred in aquifer with input of the HFFF, Sr isotope is still a sensitive indicator of the Quaternary groundwater pollution by the HFFF produced in the Dameigou shale of Qaidam Basin.     

北京市老城区雨洪控制与利用示范工程运行中的水质研究

以北京市老城区雨洪控制与利用示范工程为背景．对天然降雨、不同下垫面雨水径流、示范工程处理过程雨水径流以及地下水水质进行分析研究,通过示范工程对雨洪的处理利用效果,探讨雨水回灌至地下能否对地下水环境产生负面影响。     

南北地震带北段地壳微动态变化的初步研究

本文根据应力台站和水平形变的实际观测结果,研究了南北地震带北段1970—1983年间的区域地壳微动态变化特征及其与同时期中强地震活动的关系,得出1970—1983年本区地壳微动态变化与地球自转角速率的长期变化有关的初步结论。     

Temporal–spatial variability of atmospheric and hydrological natural disasters during recent 500 years in Inner Mongolia,China

Natural Hazards - Inner Mongolia, located in the northern China, is a natural disaster-prone region. This study is dedicated to making a comprehensive and quantitative analysis of the...     

Oderly accumulation theory of shale system petroleum resource and its prospecting significance- A case study of Chang 7 Member of Yanchang Formation in Ordos Basin

<正>1 Introduction Shale formations bear abundant mineral resource and*unconventional petroleum resource,and the unconventional petroleum resource that contain in the shale formation should be integrated and researched.