Coastal Areas Of Southeast China Research Articles

Finite Element Analysis of Seismic Wave Propagation Characteristics in Fuzhou Basin

AbstractQuantitative analysis on the ground motion triggered by the strong earthquake can be used to guide the urban planning and construction. It also plays an important role in the earthquake disaster assessment. We propose a finite element model to simulate the strong ground motion excited by earthquake. Then the peak ground acceleration (PGA) as well as the peak ground velocities are calculated accordingly with the displacement distribution with respect to the time. Fuzhou is the capital city of Fujian province, which is located in the coastal area of southeast China. It is characterized by the conspicuous basin structures with major fault zones. It is very easy to be subjected to hazards from the local strong earthquakes. This makes Fuzhou an ideal test‐bed to investigate the behaviors of the strong ground motion triggered by the possible future earthquakes. Through taking advantage of large‐scale finite element simulation, the peak ground displacements, peak ground acceleration and peak ground velocity patterns are put forward by elaborately designed post‐processing routines. These quantitative results can provide critical elements for the future urban planning, and future earthquake hazards prediction.

Mixing ratios and sources of halocarbons in urban, semi-urban and rural sites of the Pearl River Delta, South China

The pearl river delta (PRD) region is one of the most important industrial and manufacturing centers of China and the world. In order to explore the regional mixing ratios of halocarbons in the PRD atmosphere and to reconcile the major halocarbon emission sources, air samples were collected in an urban site in Guangzhou City, a semi-urban site in Panyu and a rural site on Dinghu Mountain, as well as roadside sites and vehicular tunnels of the PRD in 2001 and 2004. The samples were analyzed for a variety of carbon-containing compounds. The results revealed elevated regional mixing ratios of most halocarbons, especially trichloroethene (C 2HCl 3), methyl iodide (CH 3I), tetrachloroethene (C 2Cl 4), bromochlorodifluoromethane (Halon-1211, CBrClF 2), 1-dichloro-1,1-fluoroethane (HCFC-142b, CH 3CClF 2) and trichloromethane (CHCl 3) when compared with the background levels of the western Pacific and East Asian coast, and the Northern Hemisphere suggesting that there are significant sources of halocarbons in the PRD region. Higher dichlorodifluoromethane (CFC-12, CCl 2F 2), 1,1,1-trichlorotrifluoroethane (CFC-113, CCl 2FCClF 2), dibromomethane (CH 2Br 2) and tribromomethane (CHBr 3) mixing ratios were found in the tunnels and roadside samples when compared with the ambient samples. In these samples, CH 2Br 2 and CHBr 3 correlated well with each other and methyl bromide (CH 3Br) suggesting they are associated with exhaust emissions from vehicles running on leaded gasoline. High levels of methyl halides: methyl chloride (CH 3Cl), CH 3Br and CH 3I, and CH 2Br 2, bromodichloromethane (CHBrCl 2), CHBr 3 and dimethyl sulfide (C 2H 6S, DMS) were simultaneously observed in the oceanic air masses that originated from the coastal areas of southeast China and had passed over the Pearl River Estuary. Good correlations were found between CH 2Br 2 and CHBr 3 with linear regression slopes of 0.17 and 0.15 for the Dinghu Mountain and Guangzhou City samples, respectively, and between CH 3I and CHBr 3, and DMS suggesting that emissions from the coastal territorial ecosystems of the PRD are important sources of the methyl halides, CH 2Br 2, CHBrCl 2, CHBr 3 and DMS observed.

Examples of Settlement in Structures Constructed on Tidal Silt in Coastal Areas of Southeast China

Silt and tidal land have very low bearing strength, and they are generally very thick. Hence, the time necessary for completion of settlement of a constructed building is very long. If it is not possible to adopt deep foundation methods such as pile driving, other methods, such as soil-substitution or heavily rammed gravel bedding on the foundation can be adopted to form a better surface soil to sustain the constructed building. According to the related principles and formulas of fluid mechanics, soil mechanics, and elasticity mechanics, the author’s have found the optimum thickness of rammed gravel bedding, with better economic and social benefits.

Precipitation patterns in flood season over China associated with the El Niño/Southern Osciliation

The precipitation patterns in flood season over China associated with the El Nino/Southern Oscillation (ENSO) are investigated, especially in the eastern China, using the rather long period rainfall data in this century. The results show that there were remarkable differences between the precipitation patterns in flood seasons of ENSO warm phase (El Nino year) and cold phase (La Nina year), as well as between the patterns in El Nino years and their following years. The most parts of China received below normal rainfall in flood season of the onset years of El Nino events, but the coastal area of Southeast China received above normal amounts. Comparatively, the most parts of China received above normal rainfall in flood season of the following years of El Nino events, but the eastern part of the reaches among the Huanghe (Yellow) River, the Huaihe River and the Haihe River, and the Northeast China received less. During ENSO cold phase, the reaches of the Changjiang (Yangtze) River and the North China received more amounts than normal rainfall in flood season of the onset years of La Nina events, and the other regions of China received less. In the following years of La Nina events, the coastal area of the Southeast China, the most part of the Northeast China and the regions between the Huanghe River and the Huaihe River received more precipitation during flood seasons, but the other parts received below normal precipitation.

Geodynamic background of the mesozoic intracontinental magmatism in Southeast China

The authors have proposed a dynamic model in this paper based on the ages, rock series and associations, Sr-Nd isotopic signatures of the Mesozoic intracontinental magmatism overlying the Cathaysian and Yangtze blocks. The model describes the relation of intracontinental collision and subduction in the Tethyan tectonic regime with Paleo-Pacific oceanic plate subduction-strike slip-extension in the Pacific tectonic regime. During 220–150 Ma, the horizontal collision between the North China block and the Yangtze block, as well as the intracontinental subduction of some divergent microcontinental terranes in the southwestern part of South China are ascribed to the influence of the Tethyan tectonic regime, giving rise to a volume of high-ISr and low-ɛNd(t) S-type granites only in the Cathaysian block. During 145–90 Ma, under the geodynamic background of subduction-strike slip-extension of the Paleo-Pacific oceanic plate on the basis of the deep tectonic process in the Tethyan tectonic regime, high-K, alkali-rich calc-alkaline and shoshonitic volcano-plutonic complexes were generated in the Yangtze block, and high-K calc-alkalic and bimodal volcano-plutonic complexes were generated in the Cathaysian block. The occurrence of A-type peralkaline granites in the coastal areas of Southeast China indicates the end of Mesozoic intracontinental magmatism.

Rock-forming and ore-forming temperatures of Lianhuashan tungsten deposit, Guangdong Province

The Lianhuashan tungsten deposit occurs in the volcanic terrain in the coastal area of Southeast China, where rhyolite, quartz porphyry and granite constitute a complete magmatic series. The orebodies are located in the endo- and exo-contacts between the quartz porphyry and the metasandstone of the Xiaoping coal measures. Homogenization temperatures of melt inclusions in zircon and quartz are 1100°C and 1050°C for rhyolite, 1000°C and 860°C for quartz porphyry, and 950 – 1000°C and 820°C for granite, respectively, demonstrating that the rockforming temperatures dropped successively from the eruptive to the intrusive rocks and that the homogenization temperatures of melt inclusions in zircon are 50 – 180°C higher than those in quartz. Homogenization temperatures of gas liquid inclusions in quartz are 230 – 520°C (mostly 230 – 270°C) for quartz porphyry, 200 – 450°C (mostly 200 – 360°C) for ore-bearing quartz veins, 150– 210°C for granite and 170 – 200°C for the vein quartz in it. Quartz from the quartz porphyry and from the ore-bearing quartz veins show similar characteristics in inclusion type and homogenization temperature, indicating that intergranular solutions must have been formed upon cooling of magma and that ore-forming solutions for the tungsten mineralization were evolved mainly from ore-bearing intergranular solutions in the quartz porphyry.

Geological-geochemical characteristics of Lianhuashan porphyry tungsten deposit

The Lianhuashan porphyry tungsten deposit occurs in the coastal area of southeast China, where volcanic rocks are extensively developed. Its regional geology is related to the Benioff belt along the west Pacific Ocean during Mesozoic. Alteration-mineralization is genetically connected with quartz porphyry of Upper Jurassic age. The isochron age of the quartz porphyry was estimated at 135.8±7.3–137.8±2.4×106 yr, with an initial strontium ratio of 0.70668±0.00038. From the quartz porphyry outwards developed such alterations as potashalteration, phyllitization and propylitization. Tungsten mineralization occurs in the phyllitization zone. The mineral associations are characterized by the paragenesis of wolframite with scheelite, and high sulfides, especially pyrite, pyrrihotite and arsenopyrite. Stable isotope data are presented as follows: Evidence developed from fluid inclusions indicates that the temperature of alteration-mineralization ranges from 650° to 150°C. Ore fluids are high in salinity and rich in Cl. The geological-geochemical characteristics of the deposit permit a conclusion that the studied deposit is a porphyry-tungsten deposit.