Geology of the Yap Trench: new observations from a transect near 10°N from manned submersible Jiaolong     

Yaomin Yang  Jinwei Gao  Liyan Tian  Jichao Yang  Yue Xu 《International Geology Review》2018,60(16):1941-1953

This paper describes the petrology and geochemistry of rocks from the Yap Trench acquired by three dives of the Jiaolong research submarine. Combining the geophysical data and submersible observations, this paper describes the geomorphology, shallow structures, and sedimentology of the Yap Trench and further discusses the tectonics and activities of this region. Two obvious slope breaks are found on the landward slope, and horsts and grabens with small fault offsets are observed in the ocean-ward slope of the trench. Peridotites sampled from the Yap Trench inner wall are highly depleted subduction-related mantle residues. Volcanic rocks in the northern segment of the trench have subduction-related characteristics that Yap fore-arc rocks underwent metasomatism during Cenozoic subduction. The rocks with remarkable lithologic difference from lithospheric mantle and upper crust sampled in the break slopes suggest that the slope break area may represent a lithologic boundary or transition zone. The landward slope of the Yap Trench was removed by subduction erosion as a result of collision with the Caroline Ridge. The bending of the down-going plate caused normal faults, horsts, and grabens with little or no sediments indicating that the Caroline Ridge is subducting beneath the Yap arc along the trench even though the convergence rate is very slow.  相似文献   

Impact of recharge water temperature on bioclogging during managed aquifer recharge: a laboratory study     

Lu Xia  Zongjun Gao  Xilai Zheng  Jiuchuan Wei 《Hydrogeology Journal》2018,26(7):2173-2187

To investigate the effect of recharge water temperature on bioclogging processes and mechanisms during seasonal managed aquifer recharge (MAR), two groups of laboratory percolation experiments were conducted: a winter test and a summer test. The temperatures were controlled at ~5±2 and ~15±3 °C, and the tests involved bacterial inoculums acquired from well water during March 2014 and August 2015, for the winter and summer tests, respectively. The results indicated that the sand columns clogged ~10 times faster in the summer test due to a 10-fold larger bacterial growth rate. The maximum concentrations of total extracellular polymeric substances (EPS) in the winter test were approximately twice those in the summer test, primarily caused by a ~200 μg/g sand increase of both loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). In the first half of the experimental period, the accumulation of bacteria cells and EPS production induced rapid bioclogging in both the winter and summer tests. Afterward, increasing bacterial growth dominated the bioclogging in the summer test, while the accumulation of LB-EPS led to further bioclogging in the winter test. The biological analysis determined that the dominant bacteria in experiments for both seasons were different and the bacterial community diversity was ~50% higher in the winter test than that for summer. The seasonal inoculums could lead to differences in the bacterial community structure and diversity, while recharge water temperature was considered to be a major factor influencing the bacterial growth rate and metabolism behavior during the seasonal bioclogging process.  相似文献   

Relationships between natural terrain landslide magnitudes and triggering rainfall based on a large landslide inventory in Hong Kong     

L. Gao  L. M. Zhang  R. W. M. Cheung 《Landslides》2018,15(4):727-740

Rain-induced landslides are recognized as one of the most catastrophic hazards on hilly terrains. To develop strategies for landslide risk assessment and management, it is necessary to estimate not only the rainfall threshold for the initiation of landslides, but also the likely magnitudes of landslides triggered by a storm of a given intensity. In this study, the frequency distributions of both open hillside landslides and channelized debris flows in Hong Kong are established on the basis of the Enhanced Natural Terrain Landslide Inventory (ENTLI) with 19,763 records in Hong Kong up to 2013. The landslide magnitudes are measured in terms of the number, scar area, volume, or density of landslides. The mean values of the scar areas and volumes are 55.2 m² and 102.0 m³, respectively, for the open hillside landslides and 91.3 m² and 166.5 m³, respectively, for the channelized debris flows. Empirical correlations between the numbers, scar areas, and volumes of hillside landslides or channelized debris flows and the maximum rolling rainfall intensities of different periods have been derived. The maximum rolling 4- to 24-h rainfall amounts provide better predictions compared with those with the maximum rolling 1-h rainfall. Maximum rolling rainfall intensity-duration thresholds identifying the likely rainfall conditions that yield natural terrain landslides or debris flows of different magnitudes are also proposed. The initiation rainfall thresholds are identified as 75, 90, 100, 120, 150, 180, and 200 mm for the maximum rolling 1-, 2-, 4-, 6-, 8-, 12-, and 24-h rainfall, respectively.  相似文献   

Acquiring high-resolution topography and performing spatial analysis of loess landslides by using low-cost UAVs   总被引：1，自引：0，他引：1  

Sheng Hu  Haijun Qiu  Xingang Wang  Yu Gao  Ninglian Wang  Jiang Wu  Dongdong Yang  Mingming Cao 《Landslides》2018,15(3):593-612

The Loess Plateau is a region in China prone to frequent geological disasters, where thousands of loess landslides can be found. Conventional field survey methods are inadequate for the requirements of fine spatial analysis of landslides. Due to its numerous advantages (fast, efficient, low cost, safe, and able to acquire high-resolution data), structure from motion (SfM) technique to photogrammetric orientation of flights and modeling applied to photographs taken by unmanned aerial vehicles (UAVs) equipped with a camera has become a powerful new tool for the generation of high-resolution topography that has emerged in recent years, which has become a powerful new technique for acquiring high-resolution topographic data. In this study, we conducted nearly two months of field UAV surveys of loess landslides on the Loess Plateau, eventually established 3D digital models for 11 loess landslides, and produced high-resolution digital orthophoto maps (DOMs) and digital elevation models (DEMs). High-resolution spatial analysis of the loess landslides (mainly including characteristic parameter extraction, topography profile analysis, surface feature analysis, and hydrologic analysis) was performed using Agisoft PhotoScan, ArcGIS 10.2, Global Mapper 17, and Origin Pro 9.0. The UAV technique allows us to further understand the micro-level internal spatial and structural characteristics of loess landslides. Moreover, not only does it allow us to accurately measure the characteristic geometric parameters but also enables us to detect the surface details of loess landslides (e.g., textures, fissures, and micro-landforms). Manifestly, we can also deduce the original structural characteristics and possible inducement mechanism of landslides based on a combination of high-resolution data acquired by UAVs, proper ground surveys, and theoretical knowledge. In summary, the low-cost UAVs are highly and especially suitable for surveys and digital terrain analysis of landslides on the Loess Plateau with sparse vegetation.  相似文献   

Development of chloroplast marker for identification of Ulva species     

Gao  Dahai  Zhang  Qingchun  Sun  Zhongmin 《中国海洋湖沼学报》2022,40(6):2364-2371

Journal of Oceanology and Limnology - Large-scale Ulva-caused green tides has posed various environmental and ecological problems as well as economic consequences. It is important to identify them...  相似文献   

The increasing predominance of extreme precipitation in Southwest China since the late 1970s          下载免费PDF全文

Guowei Zheng  Yang Li  Quanliang Chen  Xin Zhou  Guolu Gao  Minggang Li  Ting Duan 《大气和海洋科学快报》2022,15(5):100227

Extreme precipitation events cause severe environmental and societal damage worldwide. Southwest China (SWC) is sensitive to such effects because of its overpopulation, underdevelopment, and fragile ecosystems. Using daily observations from 108 rain-gauge stations, the authors investigated the frequency of extreme precipitation events and their contribution to total precipitation in SWC since the late 1970s. Results indicate that total precipitation is decreasing insignificantly, but rainfall-events frequency is decreasing significantly, whereas the region is experiencing more frequent and intense extreme precipitation events. Note that although fewer stations are statistically significant, about 60% of the rain-gauge stations show an increasing trend in the frequency and intensity of extreme precipitation. Furthermore, there is an increasing trend in the contribution of total extreme precipitation to total precipitation, with extreme precipitation becoming dominant in the increasingly arid SWC region. The results carry important implications for policymakers, who should place greater emphasis on extreme precipitation and associated floods and landslides when drafting water-resource management policies.摘要本文分析了中国西南20世纪70年代末以来极端降水事件的频率, 强度及其对总降水的贡献. 结果表明, 该地区约60%的降水站点极端降水的频率和强度正在增加, 而大多数站点总降水频率明显减少. 同时极端降水总量对总降水量的贡献有显著增加的趋势, 极端降水在日益干旱的中国西南地区变得更具主导性. 研究结果提醒应更加重视极端降水及其可能引发的次生灾害, 如洪水, 山体滑坡等.  相似文献   

Shaking table test of subgrade slope reinforced by gravity retaining wall with geogrids     

Qu  Honglue  Huang  Xue  Gao  Yanan  Zhang  Zhe  Wang  Chenxu 《地震工程与工程振动(英文版)》2022,21(3):715-727

Gravity retaining wall with geogrids has showed excellent seismic performance from Wenchuan great earthquake. However, seismic damage mechanism of this kind of wall is not sufficiently clear. In view of this, a large shaking table test of the gravity retaining wall with geogrids to reinforce the subgrade slope was carried out, and based on the Hilbert-Huang transform and the marginal spectrum theory, the energy identification method of the slope dynamic failure mode was studied. The results show that the geogrids can effectively reduce displacement and rotation of the retaining wall, and it can effectively absorb the energy of the ground movement when combined with the surrounding soil. In addition, it also reveals the failure development of the gravity retaining wall with geogrids to reinforce the subgrade slope. The damage started in the deep zone near the geogrids, and then gradually extended to the surface of the subgrade slope and other zones, finally formed a continuous failure surface along the geogrids. The analysis results of the failure mode identified by the Hilbert marginal spectrum are in good consistency with the experimental results, which prove that the Hilbert marginal spectrum can be applied to obtain the seismic damage mechanism of slope.

  相似文献   

Eastward subduction of the Indian plate beneath the Indo-Myanmese arc revealed by teleseismic P-wave tomography          下载免费PDF全文

Yu Gao  Jiansi Yang  Yu Zheng 《地震科学（英文版）》2022,35(4):243-262

The deep structure of the eastward-subducting Indian plate can provide new information on the dynamics of the India-Eurasia collision. We collected and processed waveform data from temporary seismic arrays (networks) on the eastern Tibetan Plateau, seismic arrays in Northeast India and Myanmar, and permanent stations of the China Digital Seismic Network in Tibet, Gansu, Qinghai, Yunnan, and Sichuan. We combined these data with phase reports from observation stations of the International Seismological Center on the Indian plate and selected 124,808 high-quality P-wave relative travel-time residuals. Next, we used these data to invert the 3-D P-wave velocity structure of the upper mantle to a depth of 800 km beneath the eastern segment of the arcuate Himalayan orogen, at the southeastern margin of the Tibetan Plateau. The results reveal a high-angle, easterly dipping subducting plate extending more than 200 km beneath the Indo-Myanmese arc. The plate breaks off at roughly 96°E; its fragments have passed through the 410-km discontinuity (D410) into the mantle transition zone (MTZ). The MTZ beneath the Tengchong volcanic area contains a high-velocity anomaly, which does not exceed the Red River fault to the east. No other large-scale continuous subducted plates were observed in the MTZ. However, a horizontally spreading high-velocity anomaly was identified on the D410 in some regions. The anomaly may represent the negatively buoyant 90°E Ridge plate or a thickened and delaminated lithospheric block experiencing collision and compression at the southeastern margin of the Tibetan Plateau. The Tengchong volcano may originate from the mantle upwelling through the slab window formed by the break-off of the subducting Indian continental plate and oceanic plate in the upper mantle. Low-velocity upper mantle materials on the west side of the Indo-Myanmese arc may have supplemented materials to the Tengchong volcano.  相似文献   

贵州新元古代大塘坡期巨量锰矿成矿物质来源分析   总被引：1，自引：0，他引：1  

杨瑞东  高军波  徐海  罗朝坤  高磊  倪莘然  薛忠喜 《地质学报》2022,96(5):1815-1826

新元古代大塘坡期,贵州松桃等地形成锰矿集聚区,并发育4个世界级锰矿床,累计探明锰资源量达7亿t。但是什么地质条件下,能导致如此巨量的锰质富集成矿,其成矿物质来源问题一直没有得到满意的解释。本文通过对含锰岩系大塘坡组基底板溪群及海底火山岩中锰含量特征、江南造山带演化以及Rodinia超大陆解体与锰矿成矿关系分析,认为基底板溪群中锰含量高,MnO含量达到0. 16%,板溪群风化壳中锰含量更高,MnO达0. 88%。板溪群中的同期岛弧玄武岩含MnO更高,达到0. 25%,它们可能是锰矿成矿的物源层,是形成巨量锰矿的基础;江南造山带造山挤压变质作用,引起板溪群和岛弧玄武岩中锰质活化、迁移富集;Rodinia超大陆解体,在650 Ma发生拉张裂谷作用,使活化富锰变质流体沿着断裂喷流出海底,形成大量锰矿。  相似文献   

Effect of voluntary cooperativisation on livelihood capital of smallholder dairy farmers in the southwest of Bangladesh     

Uddin  Md. Ektear  Pervez  A. K. M. Kanak  Gao  Qijie 《GeoJournal》2022,87(1):111-130

GeoJournal - This study investigated the effects of voluntary cooperativisationas conducted by the Community-Based Dairy Veterinary Foundation (CDVF) on the livelihood capital of smallholder dairy...  相似文献