Linear Waveform Tomography Inversion Using Machine Learning Algorithms     

Holm-Jensen  Tue  Hansen  Thomas Mejer 《Mathematical Geosciences》2020,52(1):31-51

Mathematical Geosciences - A linear probabilistic waveform inversion strategy is proposed for crosshole tomographic data using machine learning algorithms that integrates a priori information...  相似文献   

A method for frost jacking prediction of single pile in permafrost     

Liu  Jiankun  Wang  Tengfei  Tai  Bowen  Lv  Peng 《Acta Geotechnica》2020,15(2):455-470

In this paper, a model is proposed to simulate frost jacking performances of a pile foundation within an axisymmetric pile–soil system through a coupling strategy. We consider three diversified stages for frost heave of adjacent foundation soil below freezing point, where mathematical expressions for the volumetric strain are given in terms of volumetric ice content, negative temperature and porosity. A modified strain-softening model characterizing frozen soil–pile interactions is established based on experimental results, taking into account the effects of normal pressure, negative temperature and moisture content. The proposed computational approach is then illuminated and validated via the numerical example of a simplified bridge pile foundation under natural permafrost condition. Variation of temperature regime, volumetric ice content, displacement and stress over time is analyzed. This model can be further applied to evaluating effects of different countermeasures that mitigate frost jacking hazard of single pile subjected to cold climate.

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利用InSAR获取2020年新疆于田Mw6.3地震同震形变场与断层滑动分布反演     

刘超亚  董彦芳  洪顺英  孟国杰  黄星  刘泰 《地震》2021,41(2):62-79

本文基于InSAR技术,利用欧空局Sentinel-1A/B升降轨SAR数据,提取了2020年6月26日新疆于田Mw6.3地震的同震形变场.利用升、降轨同震形变场约束,分别采用MPSO算法和Bayesian方法反演此次地震发震断层均匀滑动的几何参数,并进行对比.然后采用SDM方法获得发震断层非均匀滑动分布,并分析了同震...  相似文献   

Cold deep water in the South China Sea   总被引：1，自引：0，他引：1  

Ya-Ting Chang  Wei-Lun Hsu  Jen-Hua Tai  Tswen Yung Tang  Ming-Huei Chang  Shenn-Yu Chao 《Journal of Oceanography》2010,66(2):183-190

Two deep channels that cut through the Luzon Strait facilitate deep (>2000 m) water exchange between the western Pacific Ocean and the South China Sea. Our observations rule out the northern channel as a major exchange conduit. Rather, the southern channel funnels deep water from the western Pacific to the South China Sea at the rate of 1.06 ± 0.44 Sv (1 Sv = 10⁶ m³s⁻¹). The residence time estimated from the observed inflow from the southern channel, about 30 to 71 years, is comparable to previous estimates. The observation-based estimate of upwelling velocity at 2000 m depth is (1.10 ± 0.33) × 10⁻⁶ ms⁻¹, which is of the same order as Ekman pumping plus upwelling induced by the geostrophic current. Historical hydrographic observations suggest that the deep inflow is primarily a mixture of the Circumpolar Deep Water and Pacific Subarctic Intermediate Water. The cold inflow through the southern channel offsets about 40% of the net surface heat gain over the South China Sea. Balancing vertical advection with vertical diffusion, the estimated mean vertical eddy diffusivity of heat is about 1.21 × 10⁻³ m²s⁻¹. The cold water inflow from the southern channel maintains the shallow thermocline, which in turn could breed internal wave activities in the South China Sea.  相似文献   

Morphological Change in the Northern Red River Delta,Vietnam     

Vuong Van Bui  Daidu Fan  Dac Ve Nguyen  Dinh Lan Tran  Duc Thanh Tran  Van Long Hoang  Thi Hong Hanh Nguyen 《中国海洋大学学报(英文版)》2018,17(6):1272-1280

Coastal erosion has become a worldwide concern, typically in the densely populated Asian mega-river deltas. Severe coastal erosion in the southern Red River Delta(RRD) has been intensively studied. Coastal morphological change in the northern RRD was examined in detail through DEM(Digital Elevation Model) analysis based on time series of bathymetrical maps(1965–2004) and Landsat images(1975–2015) in this study. The results show that the northern RRD is featured by rapid coastal accretion in the past few decades, although suspended sediment flux has dropped by roughly 60% after the completeness of Hoa Binh Dam(HBD) in 1988 and relative sea level rose at 1.9 mm yr~(-1). However, accretion at the outer part of subtidal shoals and platforms was observed to slow down quickly or even turned into erosion in the last two decades. The resuspended sediments from the erosion zone can be transported landward to replenish the inner coastal zone, keeping the latter accretion in the near future to compensate for the sediment discharge decrease from the river. However, this lag effect should be terminated soon if other adverse effects go worse, e.g., damming rivers, sea-level rising, strengthening storms, land reclamation and other poor-designed coastal engineering. Coastal planners and managers should pay full attention to these changes.  相似文献   

Geological evolution,regional perspectives and hydrocarbon potential of the northwest Phu Khanh Basin,offshore Central Vietnam     

Michael B.W. Fyhn  Lars H. Nielsen  Lars O. Boldreel  Le D. Thang  Jørgen Bojesen-Koefoed  Henrik I. Petersen  Nguyen T. Huyen  Nguyen A. Duc  Nguyen T. Dau  Anders Mathiesen  Ian Reid  Dang T. Huong  Hoang A. Tuan  Le V. Hien  Hans P. Nytoft  Ioannis Abatzis 《Marine and Petroleum Geology》2009

Seismic stratigraphic and structural analyses of the northwest Phu Khanh Basin, offshore Central Vietnam, based on 2-D seismic data, indicate that the initial rifting began during the latest Cretaceous? or Palaeogene controlled by left-lateral transtension along the East Vietnam Boundary Fault Zone (EVBFZ) and northwest–southeast directed extension east of the EVBFZ. Rifting stopped due to transpression during middle Oligocene times but resumed by left-lateral transtension during the Late Oligocene. Thick sequences of lacustrine and alluvial sediments were deposited during the Palaeogene rift periods. The Late Oligocene rifting ended due to inversion, triggered by right-lateral wrenching near the Palaeogene–Neogene boundary. Following the onset of this inversion regional uplift and volcanism took place in the southern half of the study area and contemporaneous subsidence and transgression took place farther north, leading to widespread carbonate deposition. As the right-lateral wrenching decreased during the early Neogene, thermal subsidence and siliciclastic sedimentation became dominant, resulting in the buildup and southward propagation of the shelf slope. Sediment accumulation and subsidence rates increased after the Middle Miocene times due to eastward tilting of Central Vietnam and the adjacent offshore area.  相似文献   

Nearshore scavenging phenomenon elucidated by <Superscript>234</Superscript>th/<Superscript>238</Superscript>u disequilibrium in the coastal waters off Western Taiwan     

Ching-Ling Wei  Jing-Ru Tsai  Liang-Saw Wen  Su-Cheng Pai  Jen-Hua Tai 《Journal of Oceanography》2009,65(2):137-150

Dissolved and particulate ²³⁴Th activities in surface seawater were determined at 27 stations along the coastline of western Taiwan during 19–23 November 2004. Contrasting scavenging settings were observed between the northern and southern regimes of the nearshore water off western Taiwan, separated by the Cho-Shui River. The northern regime is characterized by a large quantity of suspended load contributed by northward transport of a suspension plume from the Cho-Shui River, while the southern regime, low in suspended load and high in chlorophyll concentration, is a system controlled by biological activity. A scavenging model that takes account of the physical transport was used to estimate the ²³⁴Th budget in order to estimate the scavenging and removal rates from the nearshore water. The scavenging and removal rates ranged from 21 to 127 dpm m⁻³d⁻¹ and from 36 to 525 dpm m⁻³d⁻¹, for dissolved and particulate ²³⁴Th, respectively. The removal fluxes of particulate organic carbon (POC) and particulate organic nitrogen (PON) were estimated by multiplying the particulate ²³⁴Th removal flux to the organic carbon/²³⁴Th and nitrogen/²³⁴Th ratios in suspended particles, which ranged from 4.5 to 275.2 mmol-C m⁻²d⁻¹ and from 1.3 to 50.1 mmol-N m⁻²d⁻¹, respectively. These fluxes resulted in residence times of 1∼20 days for the POC in the surface water of nearshore water off western Taiwan.  相似文献   

Tyrosinase, a new innate humoral immune parameter in large yellow croaker （Pseudosciaena crocea R）     

王淑红  王艺磊  张子平  谢芳靖  林鹏  邰振刚 《中国海洋湖沼学报》2009,27(3):527-535

We evaluated the immune response to infection with a pathogen in large yellow croaker(Pseudosciaena crocea Richardson).The fish were given an intraperitoneal(i.p.) injection of Vibrio parahaemolyticus or sterile sea water(control).We collected blood sera from the fish 0.17,1,2,4,8,12,or 16 d after injection(dpi).We measured tyrosinase activity and the concentrations of lysozyme,NOS,and antibodies.Serum tyrosinase activity was significantly higher at 0.17 and 4 dpi than in the control group,and peaked at 8 d...  相似文献   

The roles of the reversibility and irreversibility of capillary bonds on the impact dynamics of agglomerates     

Vo  Thanh-Trung  Nguyen  Trung-Kien 《Acta Geotechnica》2023,18(1):217-233

Acta Geotechnica - Wet agglomerates such as iron-ores, tablets, and aggregates are omnipresent in multi–field industries. However, our understanding of the impact dynamics of these materials...  相似文献