bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐seismic Faults and Geological Hazards and Incidence of Active Fault of Wenchuan Ms 8.0 Earthquake, Sichuan, China
Authors: MA Yinsheng , LONG Changxing , TAN Chengxuan , WANG Tao , GONG Mingquan , LIAO Chunting , WU Manlu , SHI Wei , DU Jianjun , PAN Feng 
Published: August 2010

Abstract:There are two co‐seismic faults which developed when the Wenchuan earthquake happened. One occurred along the active fault zone in the central Longmen Mts. and the other in the front of Longmen Mts. The length of which is more than 270 km and about 80 km respectively. The co‐seismic fault shows a reverse flexure belt with strike of N45°–60°E in the ground, which caused uplift at its northwest side and subsidence at the southeast. The fault face dips to the northwest with a dip angle ranging from 50° to 60°. The vertical offset of the co‐seismic fault ranges 2.5–3.0 m along the Yingxiu‐Beichuan co‐seismic fault, and 1.5–1.1 m along the Doujiangyan‐Hanwang fault. Movement of the coseismic fault presents obvious segmented features along the active fault zone in central Longmen Mts. For instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike‐slip take place. Main movement along the front Longmen Mts. shows thrust without slip and segmented features. The area of earthquake intensity more than IX degree and the distribution of secondary geological hazards occurred along the hanging wall of co‐seismic faults, and were consistent with the area of aftershock, and its width is less than 40 km from co‐seismic faults in the hanging wall. The secondary geological hazards, collapses, landslides, debris flows et al., concentrated in the hanging wall of co‐seismic fault within 0–20 km from co‐seismic fault.
Seismogenic Structure around the Epicenter of the May 12, 2008 Wenchuan Earthquake from Micro‐seismic Tomography
Authors: AN Meijian , FENG Mei , DONG Shuwen , LONG Changxing , ZHAO Yue , YANG Nong , ZHAO Wenjin , ZHANG Jizhong 
Published: August 2010

Abstract:A three‐dimensional local‐scale P‐velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event‐to‐receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of ∼2 km. The high‐resolution P‐velocity model revealed interesting structures in the seismogenic layer: (1) The Guanxian‐Anxian fault, Yingxiu‐Beichuan fault and Wenchuan‐Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; (2) The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least ∼10 km from the surface; (3) A sharp lateral velocity variation beneath the Wenchuan‐Maoxian fault may indicate that the Pengguan massif's western boundary and/or the Wenchuan‐Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu‐Beichuan and Guanxian‐Anxian faults, and vertical Wenchuan‐Maoxian fault; (4) Vicinity along the Yingxiu‐Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; (5) Two blocks of low‐velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian‐Anxian fault with a ∼7 km offset with ∼5 km vertical component.
Relationship between Crustal 3D Density Structure and the Earthquakes in the Longmenshan Range and Adjacent Areas
Authors: ZHANG Jisheng , GAO Rui , ZENG Lingsen , LI Qiusheng , GUAN Ye , HE Rizheng , WANG Haiyan , LU Zhanwu 
Published: August 2010

Abstract:This paper presents the 3D density structure of crust in the Longmenshan range and adjacent areas, with constraints from seismic and density data. The density structure of crust shows that the immense boundary plane of density distribution in relation to the Longmeshan fault belt is extended downward to ∼80 km deep. This density boundary plane dips towards the northwest and crosses the Moho. With the proximity to the Longmenshan fault belt, it has a larger magnitude of undulation in the upper and middle crust levels. Density changes abruptly across Longmeshan fault belt. Seismic data show that most of the earthquakes in the Longmenshan area after the 2008 Ms8.0 Wenchuan Earthquake occurred within the upper to middle crust. These earthquakes are clearly distributed in the uplifted region of the basement. A few of them occurs in the transitional zone between the uplifted and subsided areas. But most of the earthquakes distributes in transitional zone from subsided to uplifted areas in the upper and middle crust where relatively large density changes occurr The 3D density structure of crust in the Longmenshan and adjacent areas can thus help us to understand the pattern of overthrusting from the standpoint of deep crust and where the earthquakes occurred.
Preliminary Results of In‐situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan Ms 8.0 Earthquake
Authors: WU Manlu , ZHANG Yueqiao , LIAO Chunting , CHEN Qunce , MA Yinsheng , WU Jinsheng , YAN Junfeng , QU Mingyi 
Published: August 2010

Abstract:Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In‐situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (∼20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake.
Process Analysis of In‐situ Strain during the Ms8.0 Wenchuan Earthquake—Data from the Stress Monitoring Station at Shandan
Authors: PENG Hua , MA Xiumin , JIANG Jingjie 
Published: August 2010

Abstract:There were huge life and property losses during the Ms8.0 Wenchuan earthquake on May 12, 2008. Strain fluctuation curves were completely recorded at stress observatory stations in the Qinghai‐Tibet plateau and its surroundings in the process of the earthquake. This paper introduces the geological background of the Wenchuan earthquake and the profile of in‐situ stress monitoring stations. In particular, data of 174 earthquakes (Ms4.0–Ms8.5) were processed and analyzed with various methods, which were recorded at the Shandan station from August 2007 to December 2008. The results were compared with other seismic data, and further analyses were done for the recoded strain seismic waves, co‐seismic strain stepovers, pre‐earthquake strain valleys, Earth's free oscillations before and after the earthquake and their physical implications. During the Wenchuan earthquake, the strainmeter recorded a huge extensional strain of 70 seconds, which shows that the Wenchuan earthquake is a rupture process predominated by thrusting. Significant precursory strain anomalies were detected 48 hours, 30 hours, 8 hours and 37 minutes before the earthquake. The anomalies are very high and their forms are very similar to that of the main shock. Similar anomalies can also be found in strain curves of other shocks greater than Ms7.0, indicating that such anomalies are prevalent before a great earthquake. In this paper, it is shown that medium aftershocks (Ms5.5–6.0) can also cause Earth's free oscillations. Study of free oscillations is of great significance to understand the internal structure of the Earth and focal mechanisms of earthquakes and to recognize slow shocks, thus providing a scientific basis for the prevention and treatment of geological disasters and the prediction of future earthquakes.
A Framework of Massively Parallel Analysis of Regional Earthquake Activities
Authors: ZHANG Huai , SHI Yaolin , WU Zhongliang 
Published: August 2010

Abstract:Recent rapid progress in cyberinfrastructure in geosciences is providing seismologists an enormous boost for addressing multi‐physical phenomena of regional seismic activities. The inherent nature of their multi‐scale properties, from temporal to spatial spaces, makes it inevitably to be solved using large‐scale computations and distributed parallel data processing schemes. Under such circumstance, using the advanced numerical algorithms and unstructured mesh generation technologies become the obstacles for modern seismologists. The main objective of this paper is to present a framework, which includes a parallel finite element simulation and distributed data infrastructure, to address the novel algorithms, state‐of‐the‐art modeling and their implementation in regional seismicgenic systems. We also discuss and implement this framework to analyze the strong earthquake evolution processes in the Sichuan‐Yunnan region. This study is the key to long‐term seismic risk by estimates, providing a platform for predictive large‐scale numerical simulation modeling of regional earthquake activities.
Assessment of Geological Security and Integrated Assessment Geo‐environmental Suitability in Worst‐hit Areas in Wenchuan Quake
Authors: LI Wenpeng , WEN Dongguang , ZHOU Aiguo , SUN Xiaoming , MENG Hui , SHI Jusong , CHEN Zongyu , ZHANG Liqin , FENG Xiaoming , LIU Changli , ZHOU Jianwei 
Published: August 2010

Abstract:The Wenchuan earthquake in 2008 and geo‐hazards triggered by the earthquake caused large injuries and deaths as well as destructive damage for infrastructures like construction, traffic and electricity. It is urgent to select relatively secure areas for townships and cities constructed in high mountainous regions with high magnitude earthquakes. This paper presents the basic thoughts, evaluation indices and evaluation methods of geological security evaluation, water and land resources security demonstration and integrated assessments of geo‐environmental suitability for reconstruction in alp and ravine with high magnitude earthquakes, which are applied in the worst‐hit areas (12 counties). The integrated assessment shows that: (1) located in the Longmenshan fault zone, the evaluated area is of poor regional crust stability, in which the unstable and second unstable areas account for 79% of the total; (2) the geo‐hazards susceptibility is high in the evaluation area. The spots of geo‐hazards triggered by earthquake are mainly distributed along the active fault zone with higher distribution in the moderate and high mountains area, in which the areas of high and moderate susceptibility zoning accounts for 40.1% of the total; (3) geological security is poor in the evaluated area, in which the area of the unsuitable construction occupies 73.1%, whereas in the suitable construction area, the areas of geological security, second security and insecurity zoning account for 8.3%, 9.3% and 9.3% of the evaluated area respectively; (4) geo‐environmental suitability is poor in the evaluated area, in which the areas of suitability and basic suitability zoning account for 3.5% and 7.3% of the whole evaluation area.
Characteristics of Abnormal Pressure Systems and Their Responses of Fluid in Huatugou Oil Field, Qaidam Basin
Authors: CHEN Xiaozhi , XU Hao , TANG Dazhen , ZHANG Junfeng , HU Xiaolan , TAO Shu , CAI Yidong 
Published: August 2010

Abstract:Based on the comprehensive study of core samples, well testing data, and reservoir fluid properties, the construction and the distribution of the abnormal pressure systems of the Huatugou oil field in Qaidam Basin are discussed. The correlation between the pressure systems and hydrocarbon accumulation is addressed by analyzing the corresponding fluid characteristics. The results show that the Huatugou oil field as a whole has low formation pressure and low fluid energy; therefore, the hydrocarbons are hard to migrate, which facilitates the forming of primary reservoirs. The study reservoirs, located at the Xiayoushashan Formation (N21) and the Shangganchaigou Formation (N1) are relatively shallow and have medium porosity and low permeability. They are abnormal low‐pressure reservoirs with an average formation pressure coefficient of 0.61 and 0.72 respectively. According to the pressure coefficient and geothermal anomaly, the N1 and N21 Formations belong to two independent temperature‐pressure systems, and the former has slightly higher energy. The low‐pressure compartments consist of a distal bar as the main body, prodelta mud as the top boundary, and shore and shallow lake mud or algal mound as the bottom boundary. They are vertically overlapped and horizontally paralleled. The formation water is abundant in the Cl− ion and can be categorized as CaCl2 type with high salinity, which indicates that the abnormal low‐pressure compartments are in good sealing condition and beneficial for oil and gas accumulation and preservation.
Permeability Heterogeneity in a Fractured Sandstone–Mudstone Rock Mass in Xiaolangdi Dam Site, Central China
Authors: JIANG Xiaowei , WAN Li , WANG Xusheng , KANG Aibin , HUANG Jun , HUANG Guoxing 
Published: August 2010

Abstract:Heterogeneity of permeability in fractured media is a hot research topic in hydrogeology. Numerous approaches have been proposed to characterize heterogeneity in the last several decades. However, little attention has been paid to correlate permeability heterogeneity with geological information. In the present study, several causes of permeability heterogeneity, that is, lithology, tectonism, and depth, are identified. The unit absorption values (denoted as ω), which are results obtained from the packer test, are employed to represent permeability. The variability of permeability in sandstone–mudstone is so significant that the value of unit absorptions span 3–4 orders of magnitude at any depth with several test sections. By declustering, it has been found that under a similar tectonic history, the means of permeability differ greatly at different formations as a result of different mudrock contents. It has also been found that in the same formation, permeability can be significantly increased as a result of faulting. The well‐known phenomenon, the decrease in permeability with depth, is found to be caused by the fractures in the rock mass, and the relationship between permeability and depth can be established in the form of logω–logd. After subtracting the trend of ω with absolute depth, the mean of the residual value at each relative depth can be well correlated with the distribution of mudstone. The methods proposed in this paper can be utilized to research in similar study areas.
Major Elements in Lake Muhazi, Rwanda, East Africa
Authors: MUPENZI Jean de la Paix , GE Jiwen , HABIYAREMYE Gabriel 
Published: August 2010

Abstract:The aim of this study undertaken at Lake Muhazi in Rwanda was to determine and analyze the major elements present in water. The presence of many major elements (Al, As, Ba, C, Ca, Cu, Fe, H+, K, Mg, Mn, N, P, S, Si, and Zn) was determined by spectroscopic technique. The concentrations of the elements were measured in water samples taken from three different locations of the lake from May to August 2008. The lake is polluted by water flow from mountain sides surrounding the lake. Other causes of pollution could be the use of agrochemicals in the sugar land, which surrounds the lake, and human activities near the lake. Finally, we proposed the strategies that can be applied in order to ensure good conservation of the environment and to prevent augmentation of heavy materials into the lake.
Paleoproterozoic, High‐Metamorphic, Metasedimentary Units of Siberian Craton
Authors: URMANTSEVA Lena , TURKINA Olga 
Published: August 2010

Abstract:Sensitive, high‐resolution ion microprobe zircon U–Pb ages of Paleoproterozoic, high‐grade, metasedimentary rocks from the south‐western part of the Siberian Craton are reported. Early Precambrian, high‐grade complexes, including garnet–biotite, hypersthene–biotite, and cordierite‐bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4–3.1 Ga indicate Archean‐to‐Paleoproterozoic source provinces. Zircons from gneisses show core‐rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, ∼2.3, and 1.95–2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High‐grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high‐grade metamorphism was related to the consolidation of the Siberian Craton.
Tectonic–Hydrocarbon Accumulation of Laoyemiao Region in the Nanpu Sag, Bohai Bay Basin
Authors: ZHANG Cuimei , LIU Xiaofeng , REN Jianye 
Published: August 2010

Abstract:This paper aims to gain insight into Laoyemiao (LYM) tectonic features and utilizes the tectonic–hydrocarbon accumulation model by integrated analysis tectonic controls on suitable reservoirs, trap styles, and hydrocarbon migration. On the basis of 3‐D seismic data interpretation and the Xi'nanzhuang (XNZ) Fault geometry analysis, it has been assessed that the LYM tectonics is essentially a transverse anticline produced by flexure of the XNZ Fault surface and superimposed by Neocene north‐east‐trending strike‐slip faults. Transverse anticline is found to exert controls both on major sediment transportation pathways and sedimentary facies distribution. Fan‐delta plains that accumulated on the anticline crest near the XNZ Fault scrap and fan‐delta front on the anticline front and the upper part of both limbs slumps on synclines and the Linque subsag. In combination with the reservoir properties, suitable reservoirs are predicted in the subfacies of subaqueous distributary channel and mouth bar deposited on the anticline crest. The LYM‐faulted anticline accounts for the following trap groups: faulted‐block and anticline‐dominated trap, fault‐dominated traps, and combined and stratigraphic traps. Evidence from biomarkers of crude oil and hydrocarbon‐filling period simultaneous, or a little later to the strike‐slip fault activity, reveal that the strike‐slip faults penetrating into the deep source rock, by connecting with shallow reservoirs, provide the major hydrocarbon migration pathways.
Landslide Research at the British Geological Survey: Capture, Storage and Interpretation on a National and Site‐Specific Scale
Authors: PENNINGTON Catherine , FOSTER Claire , CHAMBERS Jonathan , JENKINS Gareth 
Published: August 2010

Abstract:Landslide research at the British Geological Survey (BGS) is carried out through a number of activities, including surveying, database development and real‐time monitoring of landslides. Landslide mapping across the UK has been carried out since BGS started geological mapping in 1835. Today, BGS geologists use a combination of remote sensing and ground‐based investigations to survey landslides. The development of waterproof tablet computers (BGS·SIGMAmobile), with inbuilt GPS and GIS for field data capture provides an accurate and rapid mapping methodology for field surveys. Regional and national mapping of landslides is carried out in conjunction with site‐specific monitoring, using terrestrial LiDAR and differential GPS technologies, which BGS has successfully developed for this application. In addition to surface monitoring, BGS is currently developing geophysical ground‐imaging systems for landslide monitoring, which provide real‐time information on subsurface changes prior to failure events. BGS's mapping and monitoring activities directly feed into the BGS National Landslide Database, the most extensive source of information on landslides in Great Britain. It currently holds over 14 000 records of landslide events. By combining BGS's corporate datasets with expert knowledge, BGS has developed a landslide hazard assessment tool, GeoSure, which provides information on the relative landslide hazard susceptibility at national scale.
Climate Change and Pastoral Economy in Kenya: A Blinking Future
Authors: HUHO Julius M. , NGAIRA Josephine K.W. , OGINDO Harun O. 
Published: August 2010

Abstract:The present paper examines the changing climatic scenarios and associated effects on livestock farming (pastoralism) in the arid and semi arid lands (ASAL) of Kenya, which cover over 80% of the country. The study was carried out in the semi arid Mukogodo Division of Laikipia District in Kenya. This division received a mean annual rainfall of approximately 507.8 mm and the main source of livelihood was pastoralism. Questionnaire, structured interview, observation and literature review were the main methods of data collection. Rainfall was used in delineating changes in climate. Standardized precipitation index (SPI) and Markov process were used in analyzing drought severity and persistence, respectively. Approximately 38% of all droughts between 1975 and 2005 were prolonged and extremely severe, with cumulative severity indices ranging between −2.54 and −6.49. The probability that normal climatic conditions persisted for two or more consecutive years in Mukogodo Division remained constant at approximately 52%. However, the probability of wet years persisting for two or more years showed a declining trend, while persistence of dry years increased with duration. A drying climatic trend was established. This drying trend in the area led to increased land degradation and encroachment of invasive nonpalatable bushes. The net effect on pastoralism was large‐scale livestock loss through starvation, disease and cattle rustling. Proper drought monitoring and accurate forecasts, community participation in all government interventions, infrastructural development in the ASAL and allocation of adequate resources for livestock development are some of the measures necessary for mitigating the dwindling pastoral economy in Kenya and other parts of the world.