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81.
Sandwaves on the Southeast Vietnam Shelf recorded by high resolution seismic profiles: formation and mechanism 总被引:1,自引:0,他引:1
Viet Dung Bui Alex Schimanski Karl Stattegger Phach Van Phung The Tiep Nguyen Tien Hai Nguyen Trung Thanh Nguyen Truong Thanh Phi 《Frontiers of Earth Science》2009,3(1):9-20
The application of high resolution seismic data using boomer sound source has revealed a wide distribution of large-scale
bedforms (sandwaves) on the Southeast Vietnam continental shelf. Bedforms that are a few meters high in wave height and hundreds
of meters long in wavelength are primarily developed in the inner shelf (20–40 m) and considered to be formed under the present-day
marine hydrodynamic conditions. Those bedforms developed in the deeper water (120 m) of the northernmost part of the continent
can be interpreted as the relict morphological features formed during the latest sea-level lowstand of the late Pleistocene
period. Two sediment transport paths have been identified on the basis of the bedform’s leeward orientation: northeast-southwest
(along-shore) and north-south (cross-shore). A quantitative bottom current map is constructed from sandwave dimensions, surface
sediments and measurement data. The strongest current velocities that gradually decrease toward the southwest are indicated
by large sandwaves in the north (field B). Water depth, surficial sediment composition and bottom current are three factors
that control the development of bedforms. 相似文献
82.
Thébault H Rodriguez Y Baena AM Andral B Barisic D Albaladejo JB Bologa AS Boudjenoun R Delfanti R Egorov VN El Khoukhi T Florou H Kniewald G Noureddine A Patrascu V Pham MK Scarpato A Stokozov NA Topcuoglu S Warnau M 《Marine pollution bulletin》2008,57(6-12):801-806
The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area. 相似文献
83.
Peter S. Fiske Charles C. Schnetzler John Mchone Kong Kham Chanthavaichith Inpong Homsombath Thonkeo Phouthakayalat Bounsou Khenthavong Pham Tich Xuan 《Meteoritics & planetary science》1999,34(5):757-761
Abstract— We have recovered 18 kg of layered tektites from 10 tektite-bearing localities in Laos and central Vietnam, including 5 localities around the town of Muong Nong (Laos). Several of these deposits originally contained several hundred kilograms of layered tektite fragments, and one fragmented mass may have been as large as 1000 kg. This is the largest single deposit of tektites yet reported. In this region, layered tektite fragments are found in isolated clusters usually associated with a pebbly laterite horizon that is 0–1 m below the surface. Near Khe Sanh, Vietnam, we estimate the abundance of layered tektite fragments to be ~100 g/m2. This is greater than five times the abundance estimated for northeast Thailand (Fiske et al., 1996). In a region that extends from northeast Thailand, through central Laos, and into central Vietnam, we found only layered tektites, which confirmed the existence of a large (>50 000 km2) subfield of the Australasian strewn field with only layered tektites. The east-west extent of the “layered-only” subfield is well constrained, but little field data exist to constrain its north-south extent. 相似文献
84.
The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian–middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO2 contents (59.9–75.1 wt%) and high K2O contents. They display typical features of I‐type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I‐type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA–ICP–MS U–Pb zircon is at 242–235 Ma, corresponding to Indosinian time. Zircon εHf values of –5.6 to –10.4, in combination with moderate Mg values of 34–45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (TDM2 = 1624–1923 Ma). 相似文献
85.
Thi Phuong Quynh Le Viet Nga Dao Emma Rochelle‐Newall Josette Garnier XiXi Lu Gilles Billen Thi Thuy Duong Cuong Tu Ho Henri Etcheber Thi Mai Huong Nguyen Thi Bich Ngoc Nguyen Bich Thuy Nguyen Nhu Da Le Quoc Long Pham 《地球表面变化过程与地形》2017,42(9):1329-1341
Riverine transport of organic carbon from terrestrial ecosystems to the oceans plays an important role in the global carbon cycle. The Red River is located in Southeast Asia where river discharge, sediment loads and fluxes of elements (carbon, nitrogen and phosphorus) associated with suspended solids have been dramatically altered over past decades as a result of reservoir impoundment and land use, population, and climate change. Dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations were measured monthly at four stations of the Red River system from January 2008 to December 2010. The results reveal that POC changed synchronically with total suspended solids (TSS) concentration and with the river discharge, whereas no clear trend was observed for DOC concentration. The mean value of total organic carbon (TOC = DOC + POC) flux in the delta of the Red River was 31.5 × 1013 ± 4.0 × 1013 MgC.yr?1 (range 27.9–35.8 × 1013 MgC.yr?1 which leads to a specific TOC flux of 2012 ± 255 kgC.km?2.yr?1 during this 2008–2010 period. About 80% of the TOC flux was transferred to the estuary during the rainy season as a consequence of the higher river water discharge. The high mean value of the POC:Chl‐a ratio (1585 ± 870 mgC.mgChl‐a?1) and the moderate C:N ratio (7.3 ± 0.1) in the water column system suggest that organic carbon in the Red River system is mainly derived from erosion and soil leaching in the basin. The effect of two new dam impoundments in the Red River was also observable with lower TOC fluxes in 2010 compared with 2008. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
86.
Pablo Santoro Mónica Fossati Pablo Tassi Nicolas Huybrechts Damien Pham Van Bang Ismael Piedra-Cueva 《国际泥沙研究》2019,34(5):444-454
The effect of the consolidation process on the morphodynamics and fine sediment dynamics of the Río de la Plata estuary is explored through a circulation-wave-sediment transport model. The consolidation model is calibrated based on settling column experimental data. Different simulations are done in order to initialize the mud layer distribution and to investigate the impact of different erosion parameter assumptions on the modeled sediment dynamics. Finally a two-year simulation is done with and without the consolidation process and realistic hydrodynamic forcings. Considering the consolidation process, the model correctly reproduces measured vertical density profiles in the Montevideo Bay access channel. The simulated suspended sediment dynamics behavior in Montevideo Bay with the consolidation process provides a more realistic deposition pattern in regard to the dredging activities. 相似文献
87.
Tuan D. Pham 《Mathematical Geology》1998,30(8):1039-1042
88.
Ghazi Babak Jeihouni Esmaeil Kisi Ozgur Pham Quoc Bao Đurin Bojan 《Theoretical and Applied Climatology》2022,149(1-2):25-37
Theoretical and Applied Climatology - In this study, statistical and soft-computing methods are compared in forecasting groundwater levels under Shared Socioeconomic Pathways (SSPs) SSP1-2.6,... 相似文献
89.
Yingnan Wang Hieu T. Tran Giang D. Nguyen Pathegama G. Ranjith Ha H. Bui 《国际地质力学数值与分析法杂志》2020,44(10):1417-1445
This paper focuses on the modelling of mixed-mode fracture using the conventional smoothed particle hydrodynamics (SPH) method and a mixed-mode cohesive fracture law embedded in the particles. The combination of conventional SPH and a mixed-mode cohesive model allows capturing fracture and separation under various loading conditions efficiently. The key advantage of this framework is its capability to represent complex fracture geometries by a set of cracked SPH particles, each of which can possess its own mixed-mode cohesive fracture with arbitrary orientations. Therefore, this can naturally capture complex fracture patterns without any predefined fracture topologies. Because a characteristic length scale related to the size of the fracture process zone is incorporated in the constitutive formulation, the proposed approach is independent from the spatial discretisation of the computational domain (or mesh independent). Furthermore, the anisotropic fracture responses of materials can be naturally captured thanks to the orientation of the fracture process zone embedded at the particle level. The performance of the proposed approach demonstrates its potentials in modelling mixed-mode fracture of rocks and similar quasi-brittle materials. 相似文献
90.
Rainfall data with an appropriate spatial resolution is a key input to hydrological models. However, networks of rain gauges are often sparsely and unevenly distributed in large catchments, especially in developing countries. High-resolution rainfall datasets, such as the Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE), the Climate Forecast System Reanalysis (CFSR), the Climatic Research Unit Time Series (CRU-TS), the Global Precipitation Climatology Centre (GPCC) and the Tropical Rainfall Measuring Mission (TRMM), have become available to overcome such limitations. The objective of this study was to evaluate the impacts of four land-based rainfall products (APHRODITE, CFSR, CRU-TS, and GPCC) and a satellite-based rainfall product (TRMM) on streamflow of the upper catchment of Tri An reservoir in Vietnam using the Hydrological Modeling System (HEC-HMS). In addition, the available rain gauges data were used for comparison purpose. Result indicates that the TRMM and GPCC data show their best match to rain gauges data in simulating the streamflow in the period 1999–2007. Generally, the results indicate that the TRMM and GPCC data could be alternative solutions. 相似文献