Light rain or moderate rain is the most common meteorological event in the rainy season in the loess area of China, so the probability of landslide hazards induced by the coupling effect of earthquakes and rainfall under the condition of light rain or moderate rain is relatively higher than that under heavy rain. To study the dynamic response characteristics and instability mechanism of loess slopes by the coupling effect of earthquakes and rainfall under the conditions of moderate rain and light rain, a low-angle slope model test of a large-scale shaking table after 10 mm of rainfall was carried out. By gradually increasing the dynamic loading, the evolution of the macroscopic deformation and the instability failure mode of the slope model are observed; the temporal and spatial trends of the amplification effect, acceleration spectrum, pore pressure and soil pressure are analyzed; and the failure mechanism of the slope is determined. The results showed that the amplification effect increased along the slope surface upward, and a strong amplification effect appeared at the front of the top of the slope. Because of the stronger dynamic stress action on the upper part of the slope, the immersed soil in the upper part of the slope experienced seismic subsidence deformation, the saturation in the seismic subsidence soil increased, and the water content temporarily increased locally. With the further increase in the loading intensity, a large number of tension cracks were generated in the seismic subsidence area, and water infiltrated down along the cracks and the wetting range expanded under dynamic action. The range of seismic subsidence and cracks further extended to the deep part of the slope. Under the reciprocating action of the subsequent ground motion, the swing amplitude of the soil mass in the seismic subsidence area, which is divided by a large number of cracks in the upper part of the slope, increased further, resulting in the further reduction in the residual strength of the seismic subsidence soil mass located at the crack tip due to the pull and shear action. Finally, under the combined action of gravity and dynamic force, the upper soil mass in the seismic subsidence area dragged the lower soil mass in the seismic subsidence area downward because the sliding force is greater than the residual strength of the soil mass, which induced a seismic subsidence-type loess landslide. Under the coupling effect of earthquakes and rainfall, the instability mode and mechanism of this landslide are significantly different from those of liquefaction-type landslides.
The South China Sea (SCS) exhibits strong variations on seasonal to interannual time scale, and the changing Southeast Asian
Monsoon has direct impacts on the nutrients and phytoplankton dynamics, as well as the carbon cycle. A Pacific basin-wide
physical-biogeochemical model has been developed and used to investigate the physical variations, ecosystem responses, and
carbon cycle consequences. The Pacific basin-wide circulation model, based on the Regional Ocean Model Systems (ROMS) with
a 50-km spatial resolution, is driven with daily air-sea fluxes derived from the National Centers for Environmental Prediction
(NCEP) reanalysis between 1990 and 2004. The biogeochemical processes are simulated with the Carbon, Si(OH)4, Nitrogen Ecosystem (CoSINE) model consisting of multiple nutrients and plankton functional groups and detailed carbon cycle
dynamics. The ROMS-CoSINE model is capable of reproducing many observed features and their variability over the same period
at the SouthEast Asian Time-series Study (SEATS) station in the SCS. The integrated air-sea CO2 flux over the entire SCS reveals a strong seasonal cycle, serving as a source of CO2 to the atmosphere in spring, summer and autumn, but acting as a sink of CO2 for the atmosphere in winter. The annual mean sea-to-air CO2 flux averaged over the entire SCS is +0.33 moles CO2 m−2year−1, which indicates that the SCS is a weak source of CO2 to the atmosphere. Temperature has a stronger influence on the seasonal variation of pCO2 than biological activity, and is thus the dominant factor controlling the oceanic pCO2 in the SCS. The water temperature, seasonal upwelling and Kuroshio intrusion determine the pCO2 differences at coast of Vietnam and the northwestern region of the Luzon Island. The inverse relationship between the interannual
variability of Chl-a in summer near the coast of Vietnam and NINO3 SST (Sea Surface Temperature) index in January implies that the carbon cycle and primary productivity in the SCS is teleconnected
to the Pacific-East Asian large-scale climatic variability. 相似文献
The I ingwu fault is in the eastern boundary of the southern section of Yinchuan graben. It hasa close relation to seismicity in the Lingwu-Wuzhong region.Few researches have been done.In this Paper,on the basis of tee data obtained from field investigation,the activity features inLate Quaternary have been discussed.The vertical displacement and its slip rate have been alsoestimated.The fault is 48km in length,being divided into 3 segments according to geologicaland topographical characteristics.The last rupture along its northern and middle segments wasoccurred in late of Late Pleistocene or early Holocene while that along the southern segmentwas occurred in midle Holocene.The vertical slip rate is estimated as 0.23~025mm/a sinceabout 66ka B.P.based on the vertical displacements of terracesⅠ,Ⅱ and Ⅲ and their ages. 相似文献